Single Board Computers | 0 articles | Tech News, Tutorials & Expert Insights

article-image-building-voice-technology-iot-projects

08 Nov 2016

10 min read

Building Voice Technology on IoT Projects

08 Nov 2016

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25394

article-image-prototyping-arduino-projects-using-python

Packt

04 Mar 2015

18 min read

Prototyping Arduino Projects using Python

Packt

04 Mar 2015

18 min read

In this article by Pratik Desai, the author of Python Programming for Arduino, we will cover the following topics: Working with pyFirmata methods Servomotor – moving the motor to a certain angle The Button() widget – interfacing GUI with Arduino and LEDs (For more resources related to this topic, see here.) Working with pyFirmata methods The pyFirmata package provides useful methods to bridge the gap between Python and Arduino's Firmata protocol. Although these methods are described with specific examples, you can use them in various different ways. This section also provides detailed description of a few additional methods. Setting up the Arduino board To set up your Arduino board in a Python program using pyFirmata, you need to specifically follow the steps that we have written down. We have distributed the entire code that is required for the setup process into small code snippets in each step. While writing your code, you will have to carefully use the code snippets that are appropriate for your application. You can always refer to the example Python files containing the complete code. Before we go ahead, let's first make sure that your Arduino board is equipped with the latest version of the StandardFirmata program and is connected to your computer: Depending upon the Arduino board that is being utilized, start by importing the appropriate pyFirmata classes to the Python code. Currently, the inbuilt pyFirmata classes only support the Arduino Uno and Arduino Mega boards: from pyfirmata import Arduino In case of Arduino Mega, use the following line of code: from pyfirmata import ArduinoMega Before we start executing any methods that is associated with handling pins, it is required to properly set the Arduino board. To perform this task, we have to first identify the USB port to which the Arduino board is connected and assign this location to a variable in the form of a string object. For Mac OS X, the port string should approximately look like this: port = '/dev/cu.usbmodemfa1331' For Windows, use the following string structure: port = 'COM3' In the case of the Linux operating system, use the following line of code: port = '/dev/ttyACM0' The port's location might be different according to your computer configuration. You can identify the correct location of your Arduino USB port by using the Arduino IDE. Once you have imported the Arduino class and assigned the port to a variable object, it's time to engage Arduino with pyFirmata and associate this relationship to another variable: board = Arduino(port) Similarly, for Arduino Mega, use this: board = ArduinoMega(port) The synchronization between the Arduino board and pyFirmata requires some time. Adding sleep time between the preceding assignment and the next set of instructions can help to avoid any issues that are related to serial port buffering. The easiest way to add sleep time is to use the inbuilt Python method, sleep(time): from time import sleep sleep(1) The sleep() method takes seconds as the parameter and a floating-point number can be used to provide the specific sleep time. For example, for 200 milliseconds, it will be sleep(0.2). At this point, you have successfully synchronized your Arduino Uno or Arduino Mega board to the computer using pyFirmata. What if you want to use a different variant (other than Arduino Uno or ArduinoMega) of the Arduino board? Any board layout in pyFirmata is defined as a dictionary object. The following is a sample of the dictionary object for the Arduino board: arduino = { 'digital' : tuple(x for x in range(14)), 'analog' : tuple(x for x in range(6)), 'pwm' : (3, 5, 6, 9, 10, 11), 'use_ports' : True, 'disabled' : (0, 1) # Rx, Tx, Crystal } For your variant of the Arduino board, you have to first create a custom dictionary object. To create this object, you need to know the hardware layout of your board. For example, an Arduino Nano board has a layout similar to a regular Arduino board, but it has eight instead of six analog ports. Therefore, the preceding dictionary object can be customized as follows: nano = { 'digital' : tuple(x for x in range(14)), 'analog' : tuple(x for x in range(8)), 'pwm' : (3, 5, 6, 9, 10, 11), 'use_ports' : True, 'disabled' : (0, 1) # Rx, Tx, Crystal } As you have already synchronized the Arduino board earlier, modify the layout of the board using the setup_layout(layout) method: board.setup_layout(nano) This command will modify the default layout of the synchronized Arduino board to the Arduino Nano layout or any other variant for which you have customized the dictionary object. Configuring Arduino pins Once your Arduino board is synchronized, it is time to configure the digital and analog pins that are going to be used as part of your program. Arduino board has digital I/O pins and analog input pins that can be utilized to perform various operations. As we already know, some of these digital pins are also capable of PWM. The direct method Now before we start writing or reading any data to these pins, we have to first assign modes to these pins. In the Arduino sketch-based, we use the pinMode function, that is, pinMode(11, INPUT) for this operation. Similarly, in pyFirmata, this assignment operation is performed using the mode method on the board object as shown in the following code snippet: from pyfirmata import Arduino from pyfirmata import INPUT, OUTPUT, PWM # Setting up Arduino board port = '/dev/cu.usbmodemfa1331' board = Arduino(port) # Assigning modes to digital pins board.digital[13].mode = OUTPUT board.analog[0].mode = INPUT The pyFirmata library includes classes for the INPUT and OUTPUT modes, which are required to be imported before you utilized them. The preceding example shows the delegation of digital pin 13 as an output and the analog pin 0 as an input. The mode method is performed on the variable assigned to the configured Arduino board using the digital[] and analog[] array index assignment. The pyFirmata library also supports additional modes such as PWM and SERVO. The PWM mode is used to get analog results from digital pins, while SERVO mode helps a digital pin to set the angle of the shaft between 0 to 180 degrees. If you are using any of these modes, import their appropriate classes from the pyFirmata library. Once these classes are imported from the pyFirmata package, the modes for the appropriate pins can be assigned using the following lines of code: board.digital[3].mode = PWM board.digital[10].mode = SERVO Assigning pin modes The direct method of configuring pin is mostly used for a single line of execution calls. In a project containing a large code and complex logic, it is convenient to assign a pin with its role to a variable object. With an assignment like this, you can later utilize the assigned variable throughout the program for various actions, instead of calling the direct method every time you need to use that pin. In pyFirmata, this assignment can be performed using the get_pin(pin_def) method: from pyfirmata import Arduino port = '/dev/cu.usbmodemfa1311' board = Arduino(port) # pin mode assignment ledPin = board.get_pin('d:13:o') The get_pin() method lets you assign pin modes using the pin_def string parameter, 'd:13:o'. The three components of pin_def are pin type, pin number, and pin mode separated by a colon (:) operator. The pin types ( analog and digital) are denoted with a and d respectively. The get_pin() method supports three modes, i for input, o for output, and p for PWM. In the previous code sample, 'd:13:o' specifies the digital pin 13 as an output. In another example, if you want to set up the analog pin 1 as an input, the parameter string will be 'a:1:i'. Working with pins As you have configured your Arduino pins, it's time to start performing actions using them. Two different types of methods are supported while working with pins: reporting methods and I/O operation methods. Reporting data When pins get configured in a program as analog input pins, they start sending input values to the serial port. If the program does not utilize this incoming data, the data starts getting buffered at the serial port and quickly overflows. The pyFirmata library provides the reporting and iterator methods to deal with this phenomenon. The enable_reporting() method is used to set the input pin to start reporting. This method needs to be utilized before performing a reading operation on the pin: board.analog[3].enable_reporting() Once the reading operation is complete, the pin can be set to disable reporting: board.analog[3].disable_reporting() In the preceding example, we assumed that you have already set up the Arduino board and configured the mode of the analog pin 3 as INPUT. The pyFirmata library also provides the Iterator() class to read and handle data over the serial port. While working with analog pins, we recommend that you start an iterator thread in the main loop to update the pin value to the latest one. If the iterator method is not used, the buffered data might overflow your serial port. This class is defined in the util module of the pyFirmata package and needs to be imported before it is utilized in the code: from pyfirmata import Arduino, util # Setting up the Arduino board port = 'COM3' board = Arduino(port) sleep(5) # Start Iterator to avoid serial overflow it = util.Iterator(board) it.start() Manual operations As we have configured the Arduino pins to suitable modes and their reporting characteristic, we can start monitoring them. The pyFirmata provides the write() and read() methods for the configured pins. The write() method The write() method is used to write a value to the pin. If the pin's mode is set to OUTPUT, the value parameter is a Boolean, that is, 0 or 1: board.digital[pin].mode = OUTPUT board.digital[pin].write(1) If you have used an alternative method of assigning the pin's mode, you can use the write() method as follows: ledPin = board.get_pin('d:13:o') ledPin.write(1) In case of the PWM signal, the Arduino accepts a value between 0 and 255 that represents the length of the duty cycle between 0 and 100 percent. The PyFiramta library provides a simplified method to deal with the PWM values as instead of values between 0 and 255, as you can just provide a float value between 0 and 1.0. For example, if you want a 50 percent duty cycle (2.5V analog value), you can specify 0.5 with the write() method. The pyFirmata library will take care of the translation and send the appropriate value, that is, 127, to the Arduino board via the Firmata protocol: board.digital[pin].mode = PWM board.digital[pin].write(0.5) Similarly, for the indirect method of assignment, you can use code similar to the following one: pwmPin = board.get_pin('d:13:p') pwmPin.write(0.5) If you are using the SERVO mode, you need to provide the value in degrees between 0 and 180. Unfortunately, the SERVO mode is only applicable for direct assignment of the pins and will be available in future for indirect assignments: board.digital[pin].mode = SERVO board.digital[pin].write(90) The read() method The read() method provides an output value at the specified Arduino pin. When the Iterator() class is being used, the value received using this method is the latest updated value at the serial port. When you read a digital pin, you can get only one of the two inputs, HIGH or LOW, which will translate to 1 or 0 in Python: board.digital[pin].read() The analog pins of Arduino linearly translate the input voltages between 0 and +5V to 0 and 1023. However, in pyFirmata, the values between 0 and +5V are linearly translated into the float values of 0 and 1.0. For example, if the voltage at the analog pin is 1V, an Arduino program will measure a value somewhere around 204, but you will receive the float value as 0.2 while using pyFirmata's read() method in Python. Servomotor – moving the motor to certain angle Servomotors are widely used electronic components in applications such as pan-tilt camera control, robotics arm, mobile robot movements, and so on where precise movement of the motor shaft is required. This precise control of the motor shaft is possible because of the position sensing decoder, which is an integral part of the servomotor assembly. A standard servomotor allows the angle of the shaft to be set between 0 and 180 degrees. The pyFirmata provides the SERVO mode that can be implemented on every digital pin. This prototyping exercise provides a template and guidelines to interface a servomotor with Python. Connections Typically, a servomotor has wires that are color-coded red, black and yellow, respectively to connect with the power, ground, and signal of the Arduino board. Connect the power and the ground of the servomotor to the 5V and the ground of the Arduino board. As displayed in the following diagram, connect the yellow signal wire to the digital pin 13: If you want to use any other digital pin, make sure that you change the pin number in the Python program in the next section. Once you have made the appropriate connections, let's move on to the Python program. The Python code The Python file consisting this code is named servoCustomAngle.py and is located in the code bundle of this book, which can be downloaded from https://www.packtpub.com/books/content/support/19610. Open this file in your Python editor. Like other examples, the starting section of the program contains the code to import the libraries and set up the Arduino board: from pyfirmata import Arduino, SERVO from time import sleep # Setting up the Arduino board port = 'COM5' board = Arduino(port) # Need to give some time to pyFirmata and Arduino to synchronize sleep(5) Now that you have Python ready to communicate with the Arduino board, let's configure the digital pin that is going to be used to connect the servomotor to the Arduino board. We will complete this task by setting the mode of pin 13 to SERVO: # Set mode of the pin 13 as SERVO pin = 13 board.digital[pin].mode = SERVO The setServoAngle(pin,angle) custom function takes the pins on which the servomotor is connected and the custom angle as input parameters. This function can be used as a part of various large projects that involve servos: # Custom angle to set Servo motor angle def setServoAngle(pin, angle): board.digital[pin].write(angle) sleep(0.015) In the main logic of this template, we want to incrementally move the motor shaft in one direction until it achieves the maximum achievable angle (180 degrees) and then move it back to the original position with the same incremental speed. In the while loop, we will ask the user to provide inputs to continue this routine, which will be captured using the raw_input() function. The user can enter character y to continue this routine or enter any other character to abort the loop: # Testing the function by rotating motor in both direction while True: for i in range(0, 180): setServoAngle(pin, i) for i in range(180, 1, -1): setServoAngle(pin, i) # Continue or break the testing process i = raw_input("Enter 'y' to continue or Enter to quit): ") if i == 'y': pass else: board.exit() break While working with all these prototyping examples, we used the direct communication method by using digital and analog pins to connect the sensor with Arduino. Now, let's get familiar with another widely used communication method between Arduino and the sensors. This is called I2C communication. The Button() widget – interfacing GUI with Arduino and LEDs Now that you have had your first hands-on experience in creating a Python graphical interface, let's integrate Arduino with it. Python makes it easy to interface various heterogeneous packages within each other and that is what you are going to do. In the next coding exercise, we will use Tkinter and pyFirmata to make the GUI work with Arduino. In this exercise, we are going to use the Button() widget to control the LEDs interfaced with the Arduino board. Before we jump to the exercises, let's build the circuit that we will need for all upcoming programs. The following is a Fritzing diagram of the circuit where we use two different colored LEDs with pull up resistors. Connect these LEDs to digital pins 10 and 11 on your Arduino Uno board, as displayed in the following diagram: While working with the code provided in this section, you will have to replace the Arduino port that is used to define the board variable according to your operating system. Also, make sure that you provide the correct pin number in the code if you are planning to use any pins other than 10 and 11. For some exercises, you will have to use the PWM pins, so make sure that you have correct pins. You can use the entire code snippet as a Python file and run it. But, this might not be possible in the upcoming exercises due to the length of the program and the complexity involved. For the Button() widget exercise, open the exampleButton.py file. The code contains three main components: pyFirmata and Arduino configurations Tkinter widget definitions for a button The LED blink function that gets executed when you press the button As you can see in the following code snippet, we have first imported libraries and initialized the Arduino board using the pyFirmata methods. For this exercise, we are only going to work with one LED and we have initialized only the ledPin variable for it: import Tkinter import pyfirmata from time import sleep port = '/dev/cu.usbmodemfa1331' board = pyfirmata.Arduino(port) sleep(5) ledPin = board.get_pin('d:11:o') As we are using the pyFirmata library for all the exercises in this article, make sure that you have uploaded the latest version of the standard Firmata sketch on your Arduino board. In the second part of the code, we have initialized the root Tkinter widget as top and provided a title string. We have also fixed the size of this window using the minsize() method. In order to get more familiar with the root widget, you can play around with the minimum and maximum size of the window: top = Tkinter.Tk() top.title("Blink LED using button") top.minsize(300,30) The Button() widget is a standard Tkinter widget that is mostly used to obtain the manual, external input stimulus from the user. Like the Label() widget, the Button() widget can be used to display text or images. Unlike the Label() widget, it can be associated with actions or methods when it is pressed. When the button is pressed, Tkinter executes the methods or commands specified by the command option: startButton = Tkinter.Button(top, text="Start", command=onStartButtonPress) startButton.pack() In this initialization, the function associated with the button is onStartButtonPress and the "Start" string is displayed as the title of the button. Similarly, the top object specifies the parent or the root widget. Once the button is instantiated, you will need to use the pack() method to make it available in the main window. In the preceding lines of code, the onStartButonPress() function includes the scripts that are required to blink the LEDs and change the state of the button. A button state can have the state as NORMAL, ACTIVE, or DISABLED. If it is not specified, the default state of any button is NORMAL. The ACTIVE and DISABLED states are useful in applications when repeated pressing of the button needs to be avoided. After turning the LED on using the write(1) method, we will add a time delay of 5 seconds using the sleep(5) function before turning it off with the write(0) method: def onStartButtonPress(): startButton.config(state=Tkinter.DISABLED) ledPin.write(1) # LED is on for fix amount of time specified below sleep(5) ledPin.write(0) startButton.config(state=Tkinter.ACTIVE) At the end of the program, we will execute the mainloop() method to initiate the Tkinter loop. Until this function is executed, the main window won't appear. To run the code, make appropriate changes to the Arduino board variable and execute the program. The following screenshot with a button and title bar will appear as the output of the program. Clicking on the Start button will turn on the LED on the Arduino board for the specified time delay. Meanwhile, when the LED is on, you will not be able to click on the Start button again. Now, in this particular program, we haven't provided sufficient code to safely disengage the Arduino board and it will be covered in upcoming exercises. Summary In this article, we learned about the Python library pyFirmata to interface Arduino to your computer using the Firmata protocol. We build a prototype using pyFirmata and Arduino to control servomotor and also developed another one with GUI, based on the Tkinter library, to control LEDs. Resources for Article: Further resources on this subject: Python Functions : Avoid Repeating Code? [article] Python 3 Designing Tasklist Application [article] The Five Kinds Of Python Functions Python 3.4 Edition [article]

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24158

article-image-raspberry-pi-4-is-up-for-sale-at-35-with-64-bit-arm-core-up-to-4gb-memory-full-throughput-gigabit-ethernet-and-more

Vincy Davis

24 Jun 2019

5 min read

Raspberry Pi 4 is up for sale at $35, with 64-bit ARM core, up to 4GB memory, full-throughput gigabit Ethernet and more!

Vincy Davis

24 Jun 2019

5 min read

Today, the Raspberry Pi 4 model is up for sale, starting at $35. It has a 1.5GHz quad-core 64-bit ARM Cortex-A72 CPU, three memory options of up to 4GB, full-throughput gigabit Ethernet, Dual-band 802.11ac wireless networking, two USB 3.0 and two USB 2.0 ports, a complete compatibility with earlier Raspberry Pi products and more. Eben Upton, Chief Executive at Raspberry Pi Trading has said that “This is a comprehensive upgrade, touching almost every element of the platform.” This is the first Raspberry Pi product available offline, since the opening of their store in Cambridge, UK. https://youtu.be/sajBySPeYH0 What’s new in Raspberry Pi 4? New Raspberry Pi silicon Previous Raspberry Pi models are based on 40nm silicon. However, the new Raspberry Pi 4 is a complete re-implementation of BCM283X on 28nm. The power saving delivered by the smaller process geometry has enabled the use of Cortex-A72 core, which has a 1.5GHz quad-core 64-bit ARM. The Cortex-A72 core can execute more instructions per clock, yielding four times performance improvement, over Raspberry Pi 3B+, depending on the benchmark. New Raspbian software The new Raspbian software provides numerous technical improvements, along with an extensively modernized user interface, and updated applications including the Chromium 74 web browser. For Raspberry Pi 4, the Raspberry team has retired the legacy graphics driver stack used on previous models and opted for the Mesa “V3D” driver. It offers benefits like OpenGL-accelerated web browsing and desktop composition, and also eliminates roughly half of the lines of closed-source code in the platform. Raspberry Pi 4 memory options For the first time, Raspberry Pi 4 is offering a choice of memory capacities, as shown below: All three variants of the new Raspberry Pi model have been launched. The entry-level Raspberry Pi 4 Model B is priced at 35$, excluding sales tax, import duty, and shipping. Additional improvements in Raspberry Pi 4 Power Raspberry Pi 4 has USB-C as the power connector, which will support an extra 500mA of current, ensuring 1.2A for downstream USB devices, even under heavy CPU load. Video The previous type-A HDMI connector has been replaced with a pair of type-D HDMI connectors, so as to accommodate dual display output within the existing board footprint. Ethernet and USB The Gigabit Ethernet magjack has been moved to the top right of the board, hence simplifying the PCB routing. The 4-pin Power-over-Ethernet (PoE) connector is in the same location, thus Raspberry Pi 4 remains compatible with the PoE HAT. The Ethernet controller on the main SoC is connected to an external Broadcom PHY, thus providing full throughput. USB is provided via an external VLI controller, connected over a single PCI Express Gen 2 lane, and providing a total of 4Gbps of bandwidth, shared between the four ports. The Raspberry Pi 4 model has the LPDDR4 memory technology, with triple bandwidth. It has also upgraded the video decode, 3D graphics, and display output to support 4Kp60 throughput. Onboard Gigabit Ethernet and PCI Express controllers have been added to address the non-multimedia I/O limitations of the previous devices. Image Source: Raspberry Pi blog New Raspberry Pi 4 accessories Due to the connector and form-factor changes, Raspberry Pi 4 has the requirement of new accessories. The Raspberry Pi 4 has its own case, priced at $5. It also has developed a suitable 5V/3A power supply, which is priced at $8 and is available in the UK, European, North American and Australian plug formats. The Raspberry Pi 4 Desktop Kit is also available and priced at $120. While the earlier Raspberry Pi models will be available in the market, Upton has mentioned that Raspberry Pi will continue to build these models as long as there's a demand for them. Users are quite ecstatic with the availability of Raspberry Pi 4 and many have already placed orders for it. https://twitter.com/Morphy99/status/1143103131821252609 https://twitter.com/M0VGA/status/1143064771446677509 A user on Reddit comments, “Very nice. Gigabit LAN and 4GB memory is opening it up to a hell of a lot more use cases. I've been tempted by some of the Pi's higher-specced competitors like the Pine64, but didn't want to lose out on the huge community behind the Pi. This seems like the best of both worlds to me.” A user on Hacker News says that “Oh my! This is such a crazy upgrade. I've been using the RPI2 as my HTPC/NAS at my folks, and I'm so happy with it. I was itching to get the last one for myself. USB 3.0! Gigabit Ethernet! WiFi 802.11ac, BT 5.0, 4GB RAM! 4K! $55 at most?! What the!? How the??! I know I'm not maintaining decorum at Hacker News, but I am SO mighty, MIGHTY excited! I'm setting up a VPN to hook this (when I get it) to my VPS and then do a LOT of fun stuff back and forth, remotely, and with the other RPI at my folks.” Another comment reads “This is absolutely great. The RPi was already exceptional for its price point, and this version seems to address the few problems it had (lack of Gigabit, USB speed and RAM capacity) and add onto it even more features. It almost seems too good to be true. Can't wait!” Another user says that “I'm most excited about the modern A72 cores, upgraded hardware decode, and up to 4 GB RAM. They really listened and delivered what most people wanted in a next gen RPi.” For more details, head over to the Raspberry Pi official blog. You can now install Windows 10 on a Raspberry Pi 3 Setting up a Raspberry Pi for a robot – Headless by Default [Tutorial] Introducing Strato Pi: An industrial Raspberry Pi

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Packt

07 Jul 2015

15 min read

Installation and Setup

Packt

07 Jul 2015

15 min read

The Banana Pi is a single-board computer, which enables you to build your own individual and versatile system. In fact, it is a complete computer, including all the required elements such as a processor, memory, network, and other interfaces, which we are going to explore. It provides enough power to run even relatively complex applications suitably. In this article by, Ryad El-Dajani, author of the book, Banana Pi Cookbook, we are going to get to know the Banana Pi device. The available distributions are mentioned, as well as how to download and install these distributions. We will also examine Android in contrast to our upcoming Linux adventure. (For more resources related to this topic, see here.) Thus, you are going to transform your little piece of hardware into a functional, running computer with a working operating system. You will master the whole process of doing the required task from connecting the cables, choosing an operating system, writing the image to an SD card, and successfully booting up and shutting down your device for the first time. Banana Pi Overview In the following picture, you see a Banana Pi on the left-hand side and a Banana Pro on the right-hand side: As you can see, there are some small differences that we need to notice. The Banana Pi provides a dedicated composite video output besides the HDMI output. However, with the Banana Pro, you can connect your display via composite video output using a four-pole composite audio/video cable on the jack. In contrast to the Banana Pi, which has 26 pin headers, the Banana Pro provides 40 pins. Also the pins for the UART port interface are located below the GPIO headers on the Pi, while they are located besides the network interface on the Pro. The other two important differences are not clearly visible on the previous picture. The operating system for your device comes in the form of image files that need to be written (burned) to an SD card. The Banana Pi uses normal SD cards while the Banana Pro will only accept Micro SD cards. Moreover, the Banana Pro provides a Wi-Fi interface already on board. Therefore, you are also able to connect the Banana Pro to your wireless network, while the Pi would require an external wireless USB device. Besides the mentioned differences, the devices are very similar. You will find the following hardware components and interfaces on your device. On the back side, you will find: A20 ARM Cortex-A7 dual core central processing unit (CPU) ARM Mali400 MP2 graphics processing unit (GPU) 1 gigabyte of DDR3 memory (that is shared with the GPU) On the front side, you will find: Ethernet network interface adapter Two USB 2.0 ports A 5V micro USB power with DC in and a micro USB OTG port A SATA 2.0 port and SATA power output Various display outputs [HDMI, LVDS, and composite (integrated into jack on the Pro)] A CSI camera input connector An infrared (IR) receiver A microphone Various hardware buttons on board (power key, reset key, and UBoot key) Various LEDs (red for power status, blue for Ethernet status, and green for user defined) As you can see, you have a lot of opportunities for letting your device interact with various external components. Operating systems for the Banana Pi The Banana Pi is capable of running any operating system that supports the ARM Cortex-A7 architecture. There are several operating systems precompiled, so you are able to write the operating system to an SD card and boot your system flawlessly. Currently, there are the following operating systems provided officially by LeMaker, the manufacturer of the Banana Pi. Android Android is a well-known operating system for mobile phones, but it is also runnable on various other devices such as smart watches, cars, and, of course, single-board computers such as the Banana Pi. The main advantage of running Android on a single-board computer is its convenience. Anybody who uses an Android-based smartphone will recognize the graphical user interface (GUI) and may have less initial hurdles. Also, setting up a media center might be easier to do on Android than on a Linux-based system. However, there are also a few disadvantages, as you are limited to software that is provided by an Android store such as Google Play. As most apps are optimized for mobile use at the moment, you will not find a lot of usable software for your Banana Pi running Android, except some Games and Multimedia applications. Moreover, you are required to use special Windows software called PhoenixCard to be able to prepare an Android SD card. In this article, we are going to ignore the installing of Android. For further information, please see Installing the Android OS image (LeMaker Wiki) at http://wiki.lemaker.org/BananaPro/Pi:SD_card_installation. Linux Most of the Linux users never realize that they are actually using Linux when operating their phones, appliances, routers, and many more products, as most of its magic happens in the background. We are going to dig into this adventure to discover its possibilities when running on our Banana Pi device. The following Linux-based operating systems—so-called distributions—are used by the majority of the Banana Pi user base and are supported officially by the manufacturer: Lubuntu: This is a lightweight distribution based on the well-known Ubuntu using the LXDE desktop, which is principally a good choice, if you are a Windows user. Raspbian: This is a distribution based on Debian, which was initially produced for the Raspberry Pi (hence the name). As a lot of Raspberry Pi owners are running Raspbian on their devices while also experimenting with the Banana Pi, LeMaker ported the original Raspbian distribution to the Banana Pi. Raspbian also comes with an LXDE desktop by default. Bananian: This too is a Debian-based Linux distribution optimized exclusively for the Banana Pi and its siblings. All of the aforementioned distributions are based on the well-known distribution, Debian. Besides the huge user base, all Debian-based distributions use the same package manager Apt (Advanced Packaging Tool) to search for and install new software, and all are similar to use. There are still more distributions that are officially supported by LeMaker, such as Berryboot, LeMedia, OpenSUSE, Fedora, Gentoo, Scratch, ArchLinux, Open MediaVault, and OpenWrt. All of them have their pros and cons or their specific use cases. If you are an experienced Linux user, you may choose your preferred distribution from the mentioned list, as most of the recipes are similar to, or even equally usable on, most of the Linux-based operating systems. Moreover, the Banana Pi community publishes various customized Linux distributions for the Banana Pi regularly. The possible advantages of a customized distribution may include enabled and optimized hardware acceleration capabilities, supportive helper scripts, fully equipped desktop environments, and much more. However, when deciding to use a customized distribution, there is no official support by LeMaker and you have to contact the publisher in case you encounter bugs, or need help. You can also check the customized Arch Linux image that author have built (http://blog.eldajani.net/banana-pi-arch-linux-customized-distribution/) for the Banana Pi and Banana Pro, including several useful applications. Downloading an operating system for the Banana Pi The following two recipes will explain how to set up the SD card with the desired operating system and how to get the Banana Pi up and running for the first time. This recipe is a predecessor. Besides the device itself, you will need at least a source for energy, which is usually a USB power supply and an SD card to boot your Banana Pi. Also, a network cable and connection is highly recommended to be able to interact with your Banana Pi from another computer via a remote shell using the application. You might also want to actually see something on a display. Then, you will need to connect your Banana Pi via HDMI, composite, or LVDS to an external screen. It is recommended that you use an HDMI Version 1.4 cable since lower versions can possibly cause issues. Besides inputting data using a remote shell, you can directly connect an USB keyboard and mouse to your Banana Pi via the USB ports. After completing the required tasks in the upcoming recipes, you will be able to boot your Banana Pi. Getting ready The following components are required for this recipe: Banana Pi SD card (minimum class 4; class 10 is recommended) USB power supply (5V 2A recommended) A computer with an SD card reader/writer (to write the image to the SD card) Furthermore, you are going to need an Internet connection to download a Linux distribution or Android. A few optional but highly recommended components are: Connection to a display (via HDMI or composite) Network connection via Ethernet USB keyboard and mouse You can acquire these items from various retailers. All items shown in the previous two pictures were bought from an online retailer that is known for originally selling books. However, the Banana Pi and the other products can be acquired from a large number of retailers. It is recommended to get a USB power supply with 2000mA (2A) output. How to do it… To download an operating system for Banana Pi, follow these steps: Download an image of your desired operating system. We are going to download Android and Raspbian from the official LeMaker image files website: http://www.lemaker.org/resources/9-38/image_files.html. The following screenshot shows the LeMaker website where you can download the official images: If you are clicking on one of the mirrors (such as Google Drive, Dropbox, and so on), you will be redirected to the equivalent file-hosting service. From there, you are actually able to download the archive file. Once your archive containing the image is downloaded, you are ready to unpack the downloaded archive, which we will do in the upcoming recipes. Setting up the SD card on Windows This recipe will explain how to set up the SD card using a Windows operating system. How to do it… In the upcoming steps, we will unpack the archive containing the operating system image for the Banana Pi and write the image to the SD card: Open the downloaded archive with 7-Zip. The following screenshot shows the 7-Zip application opening a compressed .tgz archive: Unpack the archive to a directory until you get a file with the file extension .img. If it is .tgz or .tar.gz file, you will need to unpack the archive twice Create a backup of the contents of the SD card as everything on the SD card is going to be erased unrecoverablely. Open SD Formatter (https://www.sdcard.org/downloads/formatter_4/) and check the disk letter (E: in the following screenshot). Choose Option to open the Option Setting window and choose: FORMAT TYPE: FULL (Erase) FORMAT SIZE ADJUSTMENT: ON When everything is configured correctly, check again to see whether you are using the correct disk and click Format to start the formatting process. Writing a Linux distribution image to the SD card on Windows The following steps explain how to write a Linux-based distribution to the SD card on Windows: Format the SD card using SD Formatter, which we covered in the previous section. Open the Win32 Disk Imager (http://sourceforge.net/projects/win32diskimager/). Choose the image file by clicking on the directory button. Check, whether you are going to write to the correct disk and then click on Write. Once the burning process is done, you are ready to insert the freshly prepared SD card containing your Linux operating system into the Banana Pi and boot it up for the first time. Booting up and shutting down the Banana Pi This recipe will explain how to boot up and shut down the Banana Pi. As the Banana Pi is a real computer, these tasks are as equally important as tasks on your desktop computer. The booting process starts the Linux kernel and several important services. The shutting down stops them accordingly and does not power off the Banana Pi until all data is synchronized with the SD card or external components correctly. How to do it… We are going to boot up and shut down the Banana Pi. Booting up Do the following steps to boot up your Banana Pi: Attach the Ethernet cable to your local network. Connect your Banana Pi to a display. Plug in an USB keyboard and mouse. Insert the SD card to your device. Power your Banana Pi by plugging in the USB power cable. The next screenshot shows the desktop of Raspbian after a successful boot: Shutting down Linux To shut down your Linux-based distribution, you either use the shutdown command or do it via the desktop environment (in case of Raspbian, it is called LXDE). For the latter method, these are the steps: Click on the LXDE icon in the lower-left corner. Click on Logout. Click on Shutdown in the upcoming window. To shut down your operating system via the shell, type in the following command: $ sudo shutdown -h now Connecting via SSH on Windows using PuTTY The following recipe shows you how to connect to your Banana Pi remotely using an open source application called PuTTY. Getting ready For this recipe, you will need the following ingredients: A booted up Linux operating system on your Banana Pi connected to your local network The PuTTY application on your Windows PC that is also connected to your local area network How to do it… To connect to your Banana Pi via SSH on Windows, perform the following: Run putty.exe. You will see the PuTTY Configuration dialog. Enter the IP address of the Banana Pi and leave the Port as number 22 as. Click on the Open button. A new terminal will appear, attempting a connection to the Banana Pi. When connecting to the Banana Pi for the first time, you will see a PuTTY security alert. The following screenshot shows the PuTTY Security Alert window: Trust the connection by clicking on Yes. You will be requested to enter the login credentials. Use the default username bananapi and password bananapi. When you are done, you should be welcomed by the shell of your Banana Pi. The following screenshot shows the shell of your Banana Pi accessed via SSH using PuTTY on Windows: To quit your SSH session, execute the command exit or press Ctrl + D. Searching, installing, and removing the software Once you have your decent operating system on the Banana Pi, sooner or later you are going to require a new software. As most software for Linux systems is published as open source, you can obtain the source code and compile it for yourself. One alternative is to use a package manager. A lot of software is precompiled and provided as installable packages by the so-called repositories. In case of Debian-based distributions (for example, Raspbian, Bananian, and Lubuntu), the package manager that uses these repositories is called Advanced Packaging Tool (Apt). The two most important tools for our requirements will be apt-get and apt-cache. In this recipe, we will cover the searching, the installing, and removing of software using the Apt utilities. Getting ready The following ingredients are required for this recipe. A booted Debian-based operating system on your Banana Pi An Internet connection How to do it… We will separate this recipe into searching for, installing and removing of packages. Searching for packages In the upcoming example, we will search for a solitaire game: Connect to your Banana Pi remotely or open a terminal on the desktop. Type the following command into the shell: $ apt-cache search solitaire You will get a list of packages that contain the string solitaire in their package name or description. Each line represents a package and shows the package name and description separated by a dash (-). Now we have obtained a list of solitaire games: The preceding screenshot shows the output after searching for packages containing the string solitaire using the apt-cache command. Installing a package We are going to install a package by using its package name. From the previous received list, we select the package ace-of-penguins. Type the following command into the shell: $ sudo apt-get install ace-of-penguins If asked to type the password for sudo, enter the user's password. If a package requires additional packages (dependencies), you will be asked to confirm the additional packages. In this case, enter Y. After downloading and installing, the desired package is installed: Removing a package When you want to uninstall (remove) a package, you also use the apt-get command: Type the following command into a shell: $ sudo apt-get remove ace-of-penguins If asked to type the password for sudo, enter the user's password. You will be asked to confirm the removal. Enter Y. After this process, the package is removed from your system. You will have uninstalled the package ace-of-penguins. Summary In this article, we discovered the installation of a Linux operating system on the Banana Pi. Furthermore, we connected to the Banana Pi via the SSH protocol using PuTTY. Moreover, we discussed how to install new software using the Advanced Packaging Tool. This article is a combination of parts from the first two chapters of the Banana Pi Cookbook. In the Banana Pi Cookbook, we are diving more into detail and explain the specifics of the Banana Pro, for example, how to connect to the local network via WLAN. If you are using a Linux-based desktop computer, you will also learn how to set up the SD card and connect via SSH to your Banana Pi on your Linux computer. Resources for Article: Further resources on this subject: Color and motion finding [article] Controlling the Movement of a Robot with Legs [article] Develop a Digital Clock [article]

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Packt

02 Jan 2017

20 min read

Programming with Linux

Packt

02 Jan 2017

20 min read

In this article by Edward Snajder, the author of Raspberry Pi Zero Cookbook, we pick up from having our operating system installed and our Raspberry Pi Zero on our home network. We can now dive into some basic Linux commands. You will find knowing these commands useful any time you are working on a Linux machine. In this article, we'll start prepping with some Linux recipes: (For more resources related to this topic, see here.) Navigating a filesystem and viewing and searching the contents of a directory Creating a new file, editing it in an editor, and changing ownership Renaming and copying/moving the file/folder into a new directory Installing and uninstalling a program Navigating a filesystem and viewing and searching the contents of a directory If you aren’t already a Linux or Mac user, getting around the filesystem can seem pretty alien at first. Truly, if you’ve only used Windows Explorer, this is going to seem like a strange, alien process. Once you start getting the hang of things, though, you’ll find that getting around the Linux filesystem is easy and fun. Getting ready The only thing you need to get started is a client connection to your Raspberry Pi Zero. I like to use SSH, but you can certainly connect using the serial connection or a terminal in X Windows. How to do it… If you want to find out where you are in the filesystem, use pwd: pi@rpz14101:~$ pwd /home/pi This tells me I’m in the /home/pi directory, which is the default home directory for the pi user. Generally, every user you create should get a /home/username directory to keep their own files in. This can be done automatically with user creation and the adduser command. To look at the contents of the directory you are in, use the ls command: pi@rpz14101:~$ ls Desktop Downloads Pictures python_games share Videos Documents Music Public Scratch Templates To look in another directory, simply specify the directory you want to list (you may need to use sudo depending on where you are looking): pi@rpz14101:~$ sudo ls /opt/ cookbook.share pigpio sonic-pi vc minecraft-pi share testsudo.deleteme Wolfram This is a nice quick summary of what files are in the directory, but you will usually want a little more information about the files and directories. The ls command has a ton of options, all of which can be displayed with ls –help and explained in more detail with man ls. Some of the best ones to know are as follows: -a show all files (regular and hidden) -l show long format (more file information, in columns) -h human readable (turns bytes into MB or GB as appropriate) -t or -tr order in time order, or reverse time order My typical command when I start looking in a directory is this one: ls -ltrh This produces all non-hidden files, with human-readable sizes, in column format, and the newest file at the bottom: pi@rpz14101:~$ ls -ltrh /opt/ total 513M drwxr-xr-x 7 root root 4.0K May 27 04:11 vc drwxr-xr-x 3 root root 4.0K May 27 04:32 Wolfram drwxr-xr-x 3 root root 4.0K May 27 04:34 pigpio drwxr-xr-x 4 root root 4.0K May 27 04:36 minecraft-pi drwxr-xr-x 5 root root 4.0K May 27 04:36 sonic-pi -rw-r--r-- 1 root root 0 Jul 4 13:41 testsudo.deleteme drwxr-xr-x 2 root root 4.0K Jul 9 13:05 share -rwxr-xr-x 1 root root 512M Jul 24 17:53 cookbook.share One last trick: if you need this format but there are a lot of files in the directory you are searching, you will see a ton of text scroll by. Maybe you just need the most recent or largest files? We can do this with a pipe (|) and the tail command. Let’s take a directory with a lot of files, such as /usr/lib/. To list the five most recently modified files, I can pipe ls -ltrh to the tail command: pi@rpz14101:~$ ls -ltrh /usr/lib/ | tail -5 lrwxrwxrwx 1 root root 22 May 27 04:40 libwiringPiDev.so -> libwiringPiDev.so.2.32 drwxr-xr-x 2 root root 4.0K Jun 5 10:38 samba drwxr-xr-x 3 root root 4.0K Jul 4 22:48 pppd drwxr-xr-x 65 root root 60K Jul 24 15:48 arm-linux-gnueabihf drwxr-xr-x 2 root root 4.0K Jul 24 15:48 tmpfiles.d What about the five largest files? Instead of the t in -ltrh, I can use S: pi@rpz14101:~$ ls -lSrh /usr/lib/ | tail -5 -rw-r--r-- 1 root root 2.8M Sep 17 2014 libmozjs185.so.1.0.0 -rw-r--r-- 1 root root 2.8M Sep 30 2014 libqscintilla2.so.11.3.0 -rw-r--r-- 1 root root 2.9M Jun 5 2014 libcmis-0.4.so.4.0.1 -rw-r--r-- 1 root root 3.4M Jun 12 2015 libv8.so.3.14.5 -rw-r--r-- 1 root root 5.1M Aug 18 2014 libmwaw-0.3.so.3.0.1 A little creative piping and you can find exactly the file you are looking for. If not, another great tool for exploring the filesystem is tree. This gives a pseudo-graphical tree that shows how the files are structured in the system. It produces a lot of text, especially if you have it print an entire directory tree. If just looking into directory structures, you can use tree with the -d flag for directories only. The -L flag will reduce how deep you dive into nested directories: pi@rpz14101:~$ tree -d -L 2 /opt/ /opt/ ├── minecraft-pi │ ├── api │ └── data ├── pigpio │ └── cgi ├── share ├── sonic-pi │ ├── app │ ├── bin │ └── etc ├── vc │ ├── bin │ ├── include │ ├── lib │ ├── sbin │ └── src └── Wolfram └── WolframEngine Last, we will look at a couple of searching utilities, find and grep. The find command is a powerful function that finds files in whatever directories you specify. It is great for trying to find that mystery piece of software that installed itself in an odd place or the needle-in-a-haystack file in a directory that contains hundreds of files. For example, if I were to run tree in the /opt/sonic-pi/ directory, it would run on for several seconds, and thousands of files would shoot by. I, however, am only interested in finding files with cowbell in the name. I can use the find command to look for it: pi@rpz14101:~$ find /opt/sonic-pi/ -name *cowbell* /opt/sonic-pi/etc/samples/drum_cowbell.flac When looking for anything with cowbell in the filename, the find command returns the exactly location of anything that matches. There are tons of options for using the find command; start with find –help, and then try man find when you want to get really deep. The grep command can be used in a couple different ways when searching for files, and it is one of those commands you will find yourself using constantly while both loving and hating its awesome power. Let’s say you need to find something inside of a file—grep is the tool for you. It can also find things like find can, but generally, find is more efficient at finding filename patterns than grep is. If I use grep to look for cowbells in my sonic-pi directory, I’ll get a different, and more colorful, output: We don’t see the file with cowbell in the name like we did using find, but we find every file that contains cowbell inside of it. The -r flag tells grep to delve into subdirectories, and -i tells it to ignore cases with cowbells (so Cowbell and cowbell are both found, as shown in the screenshot). As you use Linux more often, both find and grep become regularly used tools for administration and file management. This won’t be the last time you use them! Creating a new file, editing it in an editor, and changing ownership There are a lot of different text editors to use on a Linux system from the command line. The program vi is the Ubuntu default, and the program you will find installed on pretty much any Linux system. Emacs is another popular editor, and lots of Linux users get quite passionate about which one is better. My preference is vim, which is generally known as vi improved. The nano text editor is another one that is commonly installed on Linux distros, and it is one of the most lightweight editors available. Getting ready For this recipe, we will work with vi, since that’s definitely going to be installed on your system. If you want to try out vim, you can install it using this: sudo apt-get vim How to do it… First we will go to our share directory: cd /home/pi/share Then, we will create an empty file using the touch command: touch ch3_touchfile.txt If you use the ls command from the previous directory, you can see that the size of the file is 0. You can also display the contents of the file with the cat command, which will return nothing in this case. The touch command is a great way to test whether you have permissions to create files in a specific directory. You can also create a new file with the editor itself: vi ch3_vifile.txt This will open the vi editor with a blank file named ch3_vifile.txt: Using vi or vim (or Emacs) for the first time is completely different from using something like OpenOffice or Microsoft Word. Vi works in two modes: insert (or edit) and command. Once you learn how to use command mode, vi becomes a very efficient editor for working on scripts in bash or Python. Edit mode, more or less, is the mode where you can type and edit text like a regular WYSIWYG editor. There are books written on becoming a power user of vi, well beyond the scope of this book. Getting a handle on the basics is the best place to start: With the empty file, you can jump into edit mode by pressing the i or a keys. The editor will switch to insert mode, as shown by the -- INSERT -- in the bottom left of the screen. Then you can you start typing in your text: To get out of insert mode, press the Esc key. The :w command will save the file, and the :q command will quit. You can combine them, so :wq saves the file and quits. You can verify that the contents were saved with the cat command: pi@rpz14101:~$ cat ch3_vifile.txt Hello from the Raspberry Pi Zero Cookbook! Let’s take another look at the ls command and some of the information the -l format includes. We will take a look at the files we’ve created so far in this recipe: pi@rpz14101:~$ ls -ltrh *.txt -rw-r--r-- 1 pi pi 43 Jul 25 11:23 ch3_vifile.txt -rw-r--r-- 1 pi pi 0 Jul 25 11:24 ch3_touchfile.txt File Permissions Number of links Owner:Group Size Modification Date File Name -rw-r--r-- 1 pi:pi 43 Jul 25 11:23 ch3_vifile.txt We can see that since we made the files as the pi user, the owner of the file and the group owner are pi. By default, when a new user is created, a group container is created as well, so root has a root group, user rpz has an rpz group, and so on. We can change the ownership settings of a file with the chown command. Be careful, since you can take away your own access, though you can always sudo your way back. The chmod command will change who is allowed to do what with a file. Let’s look at ownership changes and what impact they will have with a few examples: pi@rpz14101:~ $ ls -ltrh *.txt -rw-r--r-- 1 pi pi 0 Jul 25 13:28 ch3_touchfile.txt -rwx------ 1 pi pi 43 Jul 25 13:28 ch3_vifile.txt pi@rpz14101:~ $ cat ch3_vifile.txt Hello from the Raspberry Pi Zero Cookbook! pi@rpz14101:~ $ sudo chown rpz:rpz ch3_vifile.txt pi@rpz14101:~ $ cat ch3_vifile.txt cat: ch3_vifile.txt: Permission denied pi@rpz14101:~ $ sudo cat ch3_vifile.txt Hello from the Raspberry Pi Zero Cookbook! pi@rpz14101:~ $ sudo chown rpz:pi ch3_vifile.txt pi@rpz14101:~ $ cat ch3_vifile.txt cat: ch3_vifile.txt: Permission denied pi@rpz14101:~ $ sudo chmod 750 ch3_vifile.txt pi@rpz14101:~ $ cat ch3_vifile.txt Hello from the Raspberry Pi Zero Cookbook! pi@rpz14101:~ $ sudo chown root:root ch3_vifile.txt pi@rpz14101:~ $ cat ch3_vifile.txt cat: ch3_vifile.txt: Permission denied pi@rpz14101:~ $ sudo chmod 755 ch3_vifile.txt pi@rpz14101:~ $ cat ch3_vifile.txt Hello from the Raspberry Pi Zero Cookbook! The chmod values are documented very well, and with a little practice, you can get your file permissions and ownership set up in a way that is both secure and easy to work with. Renaming and copying/moving the file/folder into a new directory A common activity on any filesystem is the practice of copying and moving files, and even directories, from one place to another. You might do it to make a backup copy of something, or you might decide that the contents should live in a more appropriate location. This recipe will explore how to manipulate files in the Raspbian system. Getting ready If you are still in your terminal from the last recipe, we are going to use the same files from the previous recipe. We should have the ownership back to pi:pi; if not, run the following: sudo chown pi:pi /home/pi/*.txt How to do it… First, let’s make a new directory. We’ll put it under the /home/pi/share/ folder so it is accessible to other computers on your home network. To make a directory, use the mkdir command: pi@rpz14101:~$ mkdir /home/pi/share/ch3 We can look at the new directory with the ls command: pi@rpz14101:~$ ls -ltrh /home/pi/share/ total 4.0K -rw-r--r-- 1 pi pi 0 Jul 24 15:56 helloNetwork.yes drwxr-xr-x 2 pi pi 4.0K Jul 25 13:06 ch3 A great flag to go with the mkdir command is -p. This will allow you to create directories and subdirectories in one command. Without it, if I try to create a subdirectory that doesn’t already exist, I’ll get an error: pi@rpz14101:~$ mkdir /home/pi/share/ch3/nested/folders mkdir: cannot create directory ‘/home/pi/share/ch3/nested/folders’: No such file or directory With the -p flag, it works without a problem: pi@rpz14101:~$ mkdir -p /home/pi/share/ch3/nested/folders The tree command shows the structure of our ch3 directory: pi@rpz14101:~$ tree /home/pi/share /home/pi/share ├── ch3 │ └── nested │ └── folders └── helloNetwork.yes 3 directories, 1 file Now, let’s move our files to our new ch3 directory. The copy and move commands—cp and mv, respectively—are the tools we will use. Copying a file from one place to another is as simple as indicating the file's source and destination. The following command will make a copy of vifile.txt and save it as vifile.txt.copy in the /home/pi/share/ch3/ directory: cp /home/pi/ch3_vifile.txt /home/pi/share/ch3/ch3_vifile.txt.copy We can copy files as well as directories and their contents as long as you have enough disk space. To move or rename a file, we use the mv command. This takes the file given in the source and moves it to the destination provided. As simple as the cp command, let’s move all of our files to the share directory: mv /home/pi/ch3_vifile.txt /home/pi/share/ch3/ch3_vifile.txt.moved mv /home/pi/ch3_touchfile.txt /home/pi/share/ch3/ch3_touchfile.txt If we look at the tree of our share directory, we will see everything nicely organized: pi@rpz14101:~$ tree /home/pi/share/ /home/pi/share/ ├── ch3 │ ├── ch3_touchfile.txt │ ├── ch3_vifile.txt.copy │ ├── ch3_vifile.txt.moved │ └── nested │ └── folders └── helloNetwork.yes 3 directories, 4 files Installing and uninstalling a program We’ve installed a few programs throughout the book so far, but have yet to delve into the apt-get command and the family of software-installation utilities. Now, we will learn how to install and uninstall any program available for Raspbian as well as how to search for new software and run updates. Getting ready Stay in your terminal window, and get ready to install some applications! How to do it… The apt-* commands are a suite of utilities that allow you to do various things with installed packages. To install a package, we use the apt-get tool, and the install command, like this: sudo apt-get install <packagename> Let’s install something cool—how about a Matrix screensaver? It is super easy and works great from the command line. To look for a package, we use the apt-cache search command. apt-cache is another tool in the apt-* family of utilities, and it checks the software database for matches. Running sudo apt-cache search matrix results tons of results! The word "matrix" is a little too popular for us computer and math nerds—we have matrixes everywhere! It would take forever to go through that list to find what we are looking for. Fortunately, we can take advantage of grep, which we touched on in an earlier recipe, to narrow down our results. One of the fun things about using Linux and the command line is the ways you can chain commands to do cool things: pi@rpz14101:~ $ sudo apt-cache search matrix | grep "The Matrix" cmatrix - simulates the display from "The Matrix" wmmatrix - View The Matrix in a Window Maker dock application That’s a bit more manageable! We could also have narrowed the list using this command: sudo apt-cache search “The Matrix” This returns fewer results than before, but a few more than the grep command. Whichever way you find it, we see that the cmatrix package is the one we are looking for. Installing is as simple as running this: pi@rpz14101:~ $ ` Reading package lists... Done Building dependency tree Reading state information... Done Suggested packages: cmatrix-xfont The following NEW packages will be installed: cmatrix 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. Need to get 16.2 kB of archives. After this operation, 27.6 kB of additional disk space will be used. Get:1 http://mirrordirector.raspbian.org/raspbian/ jessie/main cmatrix armhf 1.2a-5 [16.2 kB] Fetched 16.2 kB in 1s (15.3 kB/s) Selecting previously unselected package cmatrix. (Reading database ... 121906 files and directories currently installed.) Preparing to unpack .../cmatrix_1.2a-5_armhf.deb ... Unpacking cmatrix (1.2a-5) ... Processing triggers for man-db (2.7.0.2-5) ... Setting up cmatrix (1.2a-5) ... After that, we are ready to go! Channel your inner Neo and run this command: cmatrix -s -b You should be in the Matrix! Try it on your serial and SSH connections, and even in the terminal on VNC: you’ll notice differences in the rendering behavior. There are literally thousands of software packages available to install in the repositories of our awesome open source communities. Pretty much anything you think a computer should be able to do, someone, or a group of people, has worked on a solution and pushed it out to the repositories. We will be using apt-get a lot throughout this cookbook; it is one of the commands you’ll find yourself using all the time as you get more interested in Raspberry Pis and the Linux operating system. Running sudo apt-get update will check all repositories to see whether there are any version updates available. Here, you can see all of the locations it checks to see whether there is anything new for Raspbian: pi@rpz14101:~ $ sudo apt-get update Get:1 http://archive.raspberrypi.org jessie InRelease [13.2 kB] Get:2 http://mirrordirector.raspbian.org jessie InRelease [14.9 kB] Get:3 http://archive.raspberrypi.org jessie/main armhf Packages [144 kB] Get:4 http://mirrordirector.raspbian.org jessie/main armhf Packages [8,981 kB] Hit http://archive.raspberrypi.org jessie/ui armhf Packages Ign http://archive.raspberrypi.org jessie/main Translation-en_GB Get:5 http://mirrordirector.raspbian.org jessie/contrib armhf Packages [37.5 kB] Ign http://archive.raspberrypi.org jessie/main Translation-en Get:6 http://mirrordirector.raspbian.org jessie/non-free armhf Packages [70.3 kB] Ign http://archive.raspberrypi.org jessie/ui Translation-en_GB Ign http://archive.raspberrypi.org jessie/ui Translation-en Get:7 http://mirrordirector.raspbian.org jessie/rpi armhf Packages [1,356 B] Ign http://mirrordirector.raspbian.org jessie/contrib Translation-en_GB Ign http://mirrordirector.raspbian.org jessie/contrib Translation-en Ign http://mirrordirector.raspbian.org jessie/main Translation-en_GB Ign http://mirrordirector.raspbian.org jessie/main Translation-en Ign http://mirrordirector.raspbian.org jessie/non-free Translation-en_GB Ign http://mirrordirector.raspbian.org jessie/non-free Translation-en Ign http://mirrordirector.raspbian.org jessie/rpi Translation-en_GB Ign http://mirrordirector.raspbian.org jessie/rpi Translation-en Fetched 9,263 kB in 34s (272 kB/s) Reading package lists... Done After updating, apt-get upgrade will look at the versions of everything you have installed and upgrade anything to the latest version if there is one available. Depending on how many updates you have, this can take quite a while: pi@rpz14101:~ $ sudo apt-get upgrade Reading package lists... Done Building dependency tree Reading state information... Done Calculating upgrade... Done The following packages will be upgraded: dpkg-dev gir1.2-gdkpixbuf-2.0 initramfs-tools libavcodec56 libavformat56 libavresample2 libavutil54 libdevmapper-event1.02.1 libdevmapper1.02.1 libdpkg-perl python-picamera python3-picamera raspberrypi-kernel raspberrypi-net-mods ssh tzdata xarchiver 40 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. Need to get 57.0 MB of archives. After this operation, 415 kB of additional disk space will be used. Do you want to continue? [Y/n] y Get:1 http://archive.raspberrypi.org/debian/ jessie/main nodered armhf 0.14.5 [5,578 kB] … Adding 'diversion of /boot/overlays/w1-gpio.dtbo to /usr/share/rpikernelhack/overlays/w1-gpio.dtbo by rpikernelhack' … run-parts: executing /etc/kernel/postrm.d/initramfs-tools 4.4.11-v7+ /boot/kernel7.img Preparing to unpack .../raspberrypi-net-mods_1.2.3_armhf.deb ... Unpacking raspberrypi-net-mods (1.2.3) over (1.2.2) ... Processing triggers for man-db (2.7.0.2-5) ... … Setting up libssl1.0.0:armhf (1.0.1t-1+deb8u2) ... Setting up libxml2:armhf (2.9.1+dfsg1-5+deb8u2) ... … Removing 'diversion of /boot/overlays/w1-gpio-pullup.dtbo to /usr/share/rpikernelhack/overlays/w1-gpio-pullup.dtbo by rpikernelhack' … Setting up raspberrypi-net-mods (1.2.3) ... Modified /etc/network/interfaces detected. Leaving unchanged and writing new file as interfaces.new. Processing triggers for libc-bin (2.19-18+deb8u4) ... Processing triggers for initramfs-tools (0.120+deb8u2) ... You don’t really have to understand the details of what’s going on during the upgrade, and it will let you know if there were any problems at the end (and often what to do to fix them). Regularly updating and upgrading will keep all of your software current with all of the latest bug fixes and security patches. There’s more… You can also add and remove software from the GUI. If you log on to your Pi, either directly to a monitor or over VNC Server (a recipe we covered earlier), you can find the Add / Remove Software option under Menu | Preferences: The PiPackages utility makes it very easy to find software when you only have a general idea of what you are looking for. While you can do the same things with the apt commands, if you are browsing, this is a little easier on the eyes. The utility provides categorizations so you don’t have to scroll through every package. Clicking on a package provides a detailed description: Simply check the box and click on Apply or OK, and the software will be installed. Now you can install software on your Raspberry Pi Zero from the command line or GUI. Summary In this article, we looked at the basic file manipulation functionalities of Linux on a Raspberry Pi. We saw how to navigate the filesystem and create, edit, rename, copy, and move files and folders. We also saw how to change ownership of a file and install and uninstall programs. Resources for Article: Further resources on this subject: Sending Notifications using Raspberry Pi Zero [Article] Raspberry Pi LED Blueprints [Article] Hacking a Raspberry Pi project? Understand electronics first! [Article]

0
0
18524

article-image-exploring-new-reality-oculus-rift

Packt

21 Dec 2016

7 min read

Exploring a New Reality with the Oculus Rift

Packt

21 Dec 2016

7 min read

In this article by Jack Donovan the author of the book Mastering Oculus Rift Development explains about virtual reality. What made you feel like you were truly immersed in a game world for the first time? Was it graphics that looked impressively realistic, ambient noise that perfectly captured the environment and mood, or the way the game's mechanics just started to feel like a natural reflex? Game developers constantly strive to replicate scenarios that are as real and as emotionally impactful as possible, and they've never been as close as they are now with the advent of virtual reality. Virtual reality has been a niche market since the early 1950s, often failing to evoke a meaningful sense of presence that the concept hinges on—that is, until the first Oculus Rift prototype was designed in 2010 by Oculus founder Palmer Luckey. The Oculus Rift proved that modern rendering and display technology was reaching a point that an immersive virtual reality could be achieved, and that's when the new era of VR development began. Today, virtual reality development is as accessible as ever, comprehensively supported in the most popular off-the-shelf game development engines such as Unreal Engine and Unity 3D. In this article, you'll learn all of the essentials that go into a complete virtual reality experience, and master the techniques that will enable you to bring any idea you have into VR. This article will cover everything you need to know to get started with virtual reality, including the following points: The concept of virtual reality The importance of intent in VR design Common limitations of VR games (For more resources related to this topic, see here.) The concept of virtual reality Virtual reality has taken many forms and formats since its inception, but this article will be focused on modern virtual reality experienced with a Head-Mounted Display (HMD). HMDs like the Oculus Rift are typically treated like an extra screen attached to your computer (more on that later) but with some extra components that enable it to capture its own orientation (and position, in some cases). This essentially amounts to a screen that sits on your head and knows how it moves, so it can mirror your head movements in the VR experience and enable you to look around. In the following example from the Oculus developer documentation, you can see how the HMD translates this rotational data into the game world: Depth perception Depth perception is another big principle of VR. Because the display of the HMD is always positioned right in front of the user's eyes, the rendered image is typically split into two images: one per eye, with each individual image rendered from the position of that eye. You can observe the difference between normal rendering and VR rendering in the following two images. This first image is how normal 3D video games are rendered to a computer screen, created based on the position and direction of a virtual camera in the game world: This next image shows how VR scenes are rendered, using a different virtual camera for each eye to create a stereoscopic depth effect: Common limitations of VR games While virtual reality provides the ability to immerse a player's senses like never before, it also creates some new, unique problems that must be addressed by responsible VR developers. Locomotion sickness Virtual reality headsets are meant to make you feel like you're somewhere else, and it only makes sense that you'd want to be able to explore that somewhere. Unfortunately, common game mechanics like traditional joystick locomotion are problematic for VR. Our inner ears and muscular system are accustomed to sensing inertia while we move from place to place, so if you were to push a joystick forward to walk in virtual reality, your body would get confused when it sensed that you're still in a chair. Typically when there's a mismatch between what we're seeing and what we're feeling, our bodies assume that a nefarious poison or illness is at work, and they prepare to rid the body of the culprit; that's the motion sickness you feel when reading in a car, standing on a boat, and yes, moving in virtual reality. This doesn't mean that we have to prevent users from moving in VR, we just might want to be more clever about it—more on that later. The primary cause of nausea with traditional joystick movement in VR is acceleration; your brain gets confused when picking up speed or slowing down, but not so much when it's moving at a constant rate (think of being stationary in a car that's moving at a constant speed). Rotation can get even more complicated, because rotating smoothly even at a constant speed causes nausea. Some developers get around this by using hard increments instead of gradual acceleration, such as rotating in 30 degree "snaps" once per second instead of rotating smoothly. Lack of real-world vision One of the potentially clumsiest aspects of virtual reality is getting your hands where they need to be without being able to see them. Whether you're using a gamepad, keyboard, or motion controller, you'll likely need to use your hands to interact with VR—which you can't see with an HMD sitting over your eyes. It's good practice to centralize input around resting positions (i.e. the buttons naturally closest to your thumbs on a gamepad or the home row of a computer keyboard), but shy away from anything that requires complex precise input, like writing sentences on a keyboard or hitting button combos on a controller. Some VR headsets, such as the HTC Vive, have a forward-facing camera (sometimes called a passthrough camera) that users can choose to view in VR, enabling basic interaction with the real world without taking the headset off. The Oculus Rift doesn't feature a built-in camera, but you could still display the feed from an external camera on any surface in virtual reality. Even before modern VR, developers were creating applications that overlay smart information over what a camera is seeing; that's called augmented reality (AR). Experiences that ride the line between camera output and virtual environments are called mixed reality (MR). Unnatural head movements You may not have thought about it before, but looking around in a traditional first-person shooter (FPS) is quite different than looking around using your head. The right analog stick is typically used to direct the camera and make adjustments as necessary, but in VR, players actually move their head instead of using their thumb to move their virtual head. Don't expect players in VR to be able to make the same snappy pivots and 180-degree turns on a dime that are trivial in a regular console game. Summary In this article, we approached the topic of virtual reality from a fundamental level. The HMD is the crux of modern VR simulation, and it uses motion tracking components as well as peripherals like the constellation system to create immersive experiences that transport the player into a virtual world. Now that we've scratched the surface of the hardware, development techniques and use cases of virtual reality—particularly the Oculus Rift—you're probably beginning to think about what you'd like to create in virtual reality yourself Resources for Article: Further resources on this subject: Cardboard is Virtual Reality for Everyone [article] Virtually Everything for Everyone [article] Customizing the Player Character [article]

0
0
18314

article-image-build-sensor-application-measure-ambient-light

Gebin George

01 May 2018

16 min read

How to build a sensor application to measure Ambient Light

Gebin George

01 May 2018

16 min read

In today's tutorial, we will look at how to build a sensor application to measure the ambient light. Preparing our Sensor project We will create a new Universal Windows Platform application project. This time, we call it Sensor. We can use the Raspberry Pi 3, even though we will only use the light sensor and motion detector (PIR sensor) in this project. We will also add the latest version of a new NuGet package, the Waher.Persistence.FilesLW package. This package will help us with data persistence. It takes our objects and stores them in a local object database. We can later load the objects back into the memory and search for them. This is all done by analyzing the metadata available in the class definitions, so there's no need to do any database programming. Go ahead and install the package in your new project. The Waher.Persistence.Files package contains similar functionality, but it performs data encryption and dynamic code compilation of object serializes as well. These features require .NET standard v1.5, which is not compatible with the Universal Windows Platform in its current state. That is why we use the Light Weight version of the same library, which only requires .NET standard 1.3. The Universal Windows Platform supports .NET Standard up to 1.4. For more information, visit https://docs.microsoft.com/en-us/dotnet/articles/standard/library#net-platforms-support. Initializing the inventory library The next step is to initialize the libraries we have just included in the project. The persistence library includes an inventory library (Waher.Runtime.Inventory) that helps with dynamic type-related tasks, as well as keeping track of available types, interfaces and which ones have implemented which interfaces in the runtime environment. This functionality is used by the object database defined in the persistence libraries. The object database figures out how to store, load, search for, and create objects, using only their class definitions appended with a minimum of metadata in the form of attributes. So, one of the first things we need to do during startup is to tell the inventory environment which assemblies it and, by extension, the persistence library can use. We do this as follows: Log.Informational("Starting application."); Types.Initialize( typeof(FilesProvider).GetTypeInfo().Assembly, typeof(App).GetTypeInfo().Assembly); Here, Types is a static class defined in the Waher.Runtime.Inventory namespace. We initialize it by providing an array of assemblies it can use. In our case, we include the assembly of the persistence library, as well as the assembly of our own application. Initializing the persistence library We then go on to initialize our persistence library. It is accessed through the static Database class, defined in the Waher.Persistence namespace. Initialization is performed by registering one object database provider. This database provider will then be used for all object database transactions. In our case, we register our local files object database provider, FilesProvider, defined in the Waher.Persistence.Files namespace: Database.Register(new FilesProvider( Windows.Storage.ApplicationData.Current.LocalFolder.Path + Path.DirectorySeparatorChar + "Data", "Default", 8192, 1000, 8192, Encoding.UTF8, 10000)); The first parameter defines a folder where database files will be stored. In our case, we store database files in the Data subfolder of the application local data folder. Objects are divided into collections. Collections are stored in separate files and indexed differently, for performance reasons. Collections are defined using attributes in the class definition. Classes lacing a collection definition are assigned the default collection, which is specified in the second argument. Objects are then stored in B-tree ordered files. Such files are divided into blocks into which objects are crammed. For performance reasons, the block size, defined in the third argument, should be correlated to the sector size of the underlying storage medium, which is typically a power of two. This minimizes the number of reads and writes necessary. In our example, we've chosen 8,192 bytes as a suitable block size. The fourth argument defines the number of blocks the provider can cache in the memory. Caching improves performance, but requires more internal memory. In our case, we're satisfied with a relatively modest cache of 1,000 blocks (about 8 MB). Binary Large Objects (BLOBs), that is, objects that cannot efficiently be stored in a block, are stored separately in BLOB files. These are binary files consisting of doubly linked blocks. The fifth parameter controls the block size of BLOB files. The sixth parameter controls the character encoding to use when serializing strings. The seventh, and last parameter, is the maximum time the provider will wait, in milliseconds, to get access to the underlying database when an operation is to be performed. Sampling raw sensor data After the database provider has been successfully registered, the persistence layer is ready to be used. We now continue with the first step in acquiring the sensor data: sampling. Sampling is normally done using a short regular time interval. Since we use the Arduino, we get values as they change. While such values can be an excellent source for event-based algorithms, they are difficult to use in certain kinds of statistical calculations and error-correction algorithms. To set up the regular sampling of values, we begin by creating a Timer object from the System.Threading namespace, after the successful initialization of the Arduino: this.sampleTimer = new Timer(this.SampleValues, null, 1000 - DateTime.Now.Millisecond, 1000); This timer will call the SampleValues method every thousand milliseconds, starting the next second. The second parameter allows us to send a state object to the timer callback method. We will not use this, so we let it be null. We then sample the values, as follows: privateasync void SampleValues(object State) { try { ushort A0 = this.arduino.analogRead("A0"); PinState D8= this.arduino.digitalRead(8); ... } catch (Exception ex) { Log.Critical(ex); } } We define the method as asynchronous at this point, even though we still haven't used any asynchronous calls. We will do so, later in this chapter. Since the method does not return a Task object, exceptions are not propagated to the caller. This means that they must be caught inside the method to avoid unhandled exceptions closing the application. Performing basic error correction Values we sample may include different types of errors, some of which we can eliminate in the code to various degrees. There are systematic errors and random errors. Systematic errors are most often caused by the way we've constructed our device, how we sample, how the circuit is designed, how the sensors are situated, how they interact with the physical medium and our underlying mathematical model, or how we convert the sampled value into a physical quantity. Reducing systematic errors requires a deeper analysis that goes beyond the scope of this book. Random errors are errors that are induced stochastically and are often unbiased. They can be induced due to a lack of resolution or precision, by background noise, or through random events in the physical world. While background noise and the lack of resolution or precision in our electronics create a noise in the measured input, random events in the physical world may create spikes. If something briefly flutters past our light sensor, it might register a short downwards spike, even though the ambient light did not change. You'll learn how to correct for both types of random errors. Canceling noise Since the digital PIR sensor already has error correction built into it, we will only focus on how to cancel noise from our analog light sensor. Noise can be canceled electronically, using, for instance, low-pass filters. It can also be cancelled algorithmically, using a simple averaging calculation over a short window of values. The averaging calculation will increase our resolution, at the cost of a small delay in the output. If we perform the average over 10 values, we effectively gain one power of 10, or one decimal, of resolution in our output value. The value will be delayed 10 seconds, however. This algorithm is therefore only suitable for input signals that vary slowly, or where a quick reaction to changes in the input stimuli is not required. Statistically, the expected average value is the same as the expected value, if the input is a steady signal overlaid with random noise. The implementation is simple. We need the following variables to set up our averaging algorithm: privateconstintwindowSize = 10; privateint?[] windowA0 = new int?[windowSize]; privateint nrA0 = 0; privateint sumA0 = 0; We use nullable integers (int?), to be able to remove bad values later. In the beginning, all values are null. After sampling the value, we first shift the window one step, and add our newly sampled value at the end. We also update our counters and sums. This allows us to quickly calculate the average value of the entire window, without having to loop through it each time: if (this.windowA0[0].HasValue) { this.sumA0 -= this.windowA0[0].Value; this.nrA0--; } Array.Copy(this.windowA0, 1, this.windowA0, 0, windowSize - 1); this.windowA0[windowSize - 1] = A0; this.sumA0 += A0; this.nrA0++; double AvgA0 = ((double)this.sumA0) / this.nrA0; int? v; Removing random spikes We now have a value that is 10 times more accurate than the original, in cases where our ambient light is not expected to vary quickly. This is typically the case, if ambient light depends on the sun and weather. Calculating the average over a short window has an added advantage: it allows us to remove bad measurements, or spikes. When a physical quantity changes, it normally changes continuously, slowly, and smoothly. This will have the effect that roughly half of the measurements, even when the input value changes, will be on one side of the average value, and the other half on the other side. A single spike, on the other hand, especially in the middle of the window, if sufficiently large, will stand out alone on one side, while the other values remain on the other. We can use this fact to remove bad measurements from our window. We define our middle position first: private const int spikePos = windowSize / 2; We proceed by calculating the number of values on each side of the average, if our window is sufficiently full: if (this.nrA0 >= windowSize - 2) { int NrLt = 0; int NrGt = 0; foreach (int? Value in this.windowA0) { if (Value.HasValue) { if (Value.Value < AvgA0) NrLt++; else if (Value.Value > AvgA0) NrGt++; } } If we only have one value on one side, and this value happens to be in the middle of the window, we identify it as a spike and remove it from the window. We also make sure to adjust our average value accordingly: if (NrLt == 1 || NrGt == 1) { v = this.windowA0[spikePos]; if (v.HasValue) { if ((NrLt == 1 && v.Value < AvgA0) || (NrGt == 1 && v.Value > AvgA0)) { this.sumA0 -= v.Value; this.nrA0--; this.windowA0[spikePos] = null; AvgA0 = ((double)this.sumA0) / this.nrA0; } } } } Since we remove the spike when it reaches the middle of the window, it might pollute the average of the entire window up to that point. We therefore need to recalculate an average value for the half of the window, where any spikes have been removed. This part of the window is smaller, so the resolution gain is not as big. Instead, the average value will not be polluted by single spikes. But we will still have increased the resolution by a factor of five: int i, n; for (AvgA0 = i = n = 0; i < spikePos; i++) { if ((v = this.windowA0[i]).HasValue) { n++; AvgA0 += v.Value; } } if (n > 0) { AvgA0 /= n; Converting to a physical quantity It is not sufficient for a sensor to have a numerical raw value of the measured quantity. It only tells us something if we know something more about the raw value. We must, therefore, convert it to a known physical unit. We must also provide an estimate of the precision (or error) the value has. A sensor measuring a physical quantity should report a numerical value, its physical unit, and the corresponding precision, or error of the estimate. To avoid creating a complex mathematical model that converts our measured light intensity into a known physical unit, which would go beyond the scope of this book, we convert it to a percentage value. Since we've gained a factor of five of precision using our averaging calculation, we can report two decimals of precision, even though the input value is only 1,024 bits, and only contains one decimal of precision: double Light = (100.0 * AvgA0) / 1024; MainPage.Instance.LightUpdated(Light, 2, "%"); } Illustrating measurement results Following image shows how our measured quantity behaves. The light sensor is placed in broad daylight on a sunny day, so it's saturated. Things move in front of the sensor, creating short dips. The thin blue line is a scaled version of our raw input A0. Since this value is event based, it is being reported more often than once a second. Our red curve is our measured, and corrected, ambient light value, in percent. The dots correspond to our second values. Notice that the first two spikes are removed and don't affect the measurement, which remains close to 100%. Only the larger dips affect the measurement. Also, notice the small delay inherent in our algorithm. It is most noticeable if there are abrupt changes: If we, on the other hand, have a very noisy input, our averaging algorithm helps our measured value to stay more stable. Perhaps the physical quantity goes below some sensor threshold, and input values become uncertain. In the following image, we see how the floating average varies less than the noisy input: Calculating basic statistics A sensor normally reports more than the measured momentary value. It also calculates basic statistics on the measured input, such as peak values. It also makes sure to store measured values regularly, to allow its users to view historical measurements. We begin by defining variables to keep track of our peak values: private int? lastMinute = null; private double? minLight = null; private double? maxLight = null; private DateTime minLightAt = DateTime.MinValue; private DateTime maxLightAt = DateTime.MinValue; We then make sure to update these after having calculated a new measurement: DateTime Timestamp = DateTime.Now; if (!this.minLight.HasValue || Light < this.minLight.Value) { this.minLight = Light; this.minLightAt = Timestamp; } if (!this.maxLight.HasValue || Light > this.maxLight.Value) { this.maxLight = Light; this.maxLightAt = Timestamp; } Defining data persistence The last step in this is to store our values regularly. Later, when we present different communication protocols, we will show how to make these values available to users. Since we will use an object database to store our data, we need to create a class that defines what to store. We start with the class definition: [TypeName(TypeNameSerialization.None)] [CollectionName("MinuteValues")] [Index("Timestamp")] public class LastMinute { [ObjectId] public string ObjectId = null; } The class is decorated with a couple of attributes from the Waher.Persistence.Attributes namespace. The CollectionName attribute defines the collection in which objects of this class will be stored. The TypeName attribute defines if we want the type name to be stored with the data. This is useful, if you mix different types of classes in the same collection. We plan not to, so we choose not to store type names. This saves some space. The Index attribute defines an index. This makes it possible to do quick searches. Later, we will want to search historical records based on their timestamps, so we add an index on the Timestamp field. We also define an Object ID field. This is a special field that is like a primary key in object databases. We need it to be able to delete objects later. You can add any number of indices and any number of fields in each index. Placing a hyphen (-) before the field name makes the engine use descending sort order for that field. Next, we define some member fields. If you want, you can use properties as well, if you provide both getters and setters for the properties you wish to persist. By providing default values, and decorating the fields (or properties) with the corresponding default value, you can optimize storage somewhat. Only members with values different from the declared default values will then be persisted, to save space: [DefaultValueDateTimeMinValue] public DateTime Timestamp = DateTime.MinValue; [DefaultValue(0)] public double Light = 0; [DefaultValue(PinState.LOW)] public PinState Motion= PinState.LOW; [DefaultValueNull] public double? MinLight = null; [DefaultValueDateTimeMinValue] public DateTime MinLightAt = DateTime.MinValue; [DefaultValueNull] public double? MaxLight = null; [DefaultValueDateTimeMinValue] public DateTime MaxLightAt = DateTime.MinValue; Storing measured data We are now ready to store our measured data. We use the lastMinute field defined earlier to know when we pass into a new minute. We use that opportunity to store the most recent value, together with the basic statistics we've calculated: if (!this.lastMinute.HasValue) this.lastMinute = Timestamp.Minute; else if (this.lastMinute.Value != Timestamp.Minute) { this.lastMinute = Timestamp.Minute; We begin by creating an instance of the LastMinute class defined earlier: LastMinute Rec = new LastMinute() { Timestamp = Timestamp, Light = Light, Motion= D8, MinLight = this.minLight, MinLightAt = this.minLightAt, MaxLight = this.maxLight, MaxLightAt = this.maxLightAt }; Storing this object is very easy. The call is asynchronous and can be executed in parallel, if desired. We choose to wait for it to complete, since we will be making database requests after the operation has completed: await Database.Insert(Rec); We then clear our variables used for calculating peak values, to make sure peak values are calculated within the next period: this.minLight = null; this.minLightAt = DateTime.MinValue; this.maxLight = null; this.maxLightAt = DateTime.MinValue; } Removing old data We cannot continue storing new values without also having a plan for removing old ones. Doing so is easy. We choose to delete all records older than 100 minutes. This is done by first performing a search, and then deleting objects that are found in this search. The search is defined by using filters from the Waher.Persistence.Filters namespace: foreach (LastMinute Rec2 in await Database.Find<LastMinute>( new FilterFieldLesserThan("Timestamp", Timestamp.AddMinutes(-100)))) { await Database.Delete(Rec2); } You can now execute the application, and monitor how the MinuteValues collection is being filled. We created a simple sensor app for the Raspberry Pi using C#. You read an excerpt from the book, Mastering Internet of Things, written by Peter Waher. This book will help you augment your IoT skills with the help of engaging and enlightening tutorials designed for Raspberry Pi 3. 25 Datasets for Deep Learning in IoT How IoT is going to change tech teams How to run and configure an IoT Gateway

0
0
17898

article-image-getting-started-beaglebone

Packt

27 Sep 2016

36 min read

Getting Started with BeagleBone

Packt

27 Sep 2016

36 min read

0
1
17309

article-image-sending-notifications-using-raspberry-pi-zero

Packt

12 Oct 2016

6 min read

Sending Notifications using Raspberry Pi Zero

Packt

12 Oct 2016

6 min read

In this article by Marco Schwartz, author of Building Smart Homes with Raspberry Pi Zero, we are going to start diving into a very interesting field that will change the way we interact with our environment: the Internet of Things (IoT). The IoT basically proposes to connect every device around us to the Internet, so we can interact with them from anywhere in the world. (For more resources related to this topic, see here.) Within this context, a very important application is to receive notifications from your devices when they detect something in your home, for example a motion in your home or the current temperature. This is exactly what we are going to do in this article, we are going to learn how to make your Raspberry Pi Zero board send you notifications via text message, email, and push notifications. Let's start! Hardware and software requirements As always, we are going to start with the list of required hardware and software components for the project. Except Raspberry Pi Zero, you will need some additional components for each of the sections in this article. For the project of this article, we are going to use a simple PIR motion sensor to detect motion from your Pi. Then, for the last two projects of the article, we'll use the DHT11 sensor. Finally, you will need the usual breadboard and jumper wires. This is the list of components that you will need for this whole article, not including the Raspberry Pi Zero: PIR motion sensor (https://www.sparkfun.com/products/13285) DHT11 sensor + 4.7k Ohm resistor (https://www.adafruit.com/products/386) Breadboard (https://www.adafruit.com/products/64) Jumper wires (https://www.adafruit.com/products/1957) On the software side, you will need to create an account on IFTTT, which we will use in all the projects of this article. For that, simply go to: https://ifttt.com/ You should be redirected to the main page of IFTTT where you'll be able to create an account: Making a motion sensor that sends text messages For the first project of this chapter, we are going to attach a motion sensor to the Raspberry Pi board and make the Raspberry Pi Zero send us a text message whenever motion is detected. For that, we are going to use IFTTT to make the link between our Raspberry Pi and our phone. Indeed, whenever IFTTT will receive a trigger from the Raspberry Pi, it will automatically send us a text message. Lets first connect the PIR motion sensor to the Raspberry Pi. For that, simply connect the VCC pin of the sensor to a 3.3V pin of the Raspberry Pi, GND to GND, and the OUT pin of the sensor to GPIO18 of the Raspberry Pi. This is the final result: Let's now add our first channel to IFTTT, which will allow us later to interact with the Raspberry Pi and with web services. You can easily add new channels by clicking on the corresponding tab on the IFTTT website. First, add the Maker channel to your account: This will basically give you a key that you will need when writing the code for this project: After that, add the SMS channel to your IFTTT account. Now, you can actually create your first recipe. Select the Maker channel as the trigger channel: Then, select Receive a web request: As the name of this request, enter motion_detected: As the action channel, which is the channel that will be executed when a trigger is received, choose the SMS channel: For the action, choose Send me an SMS: You can now enter the message you want to see in the text messages: Finally, confirm the creation of the recipe: Now that our recipe is created and active, we can move on to actually configuring Raspberry Pi so it sends alerts whenever a motion is detected. As usual, we'll use Node.js to code this program. After a minute, pass your hand in front of the sensor: your Raspberry Pi should immediately send a command to IFTTT and after some seconds you should be able to receive a message on your mobile phone: Congratulations, you can now use your Raspberry Pi Zero to send important notifications, on your mobile phone! Note that for an actual use of this project in your home, you might want to limit the number of messages you are sending as IFTTT has a limit on the number of messages you can send (check the IFTTT website for the current limit). For example, you could use this for only very important alerts, like in case of an intruder coming in your home in your absence. Sending temperature alerts through email In the second project of the article, we are going to learn how to send automated email alerts based on data measured by the Raspberry Pi. Let's first assemble the project. Place the DHT11 sensor on the breadboard and then place the 4.7k Ohm resistor between pin 1 and 2 of the sensor. Then, connect pin 1 of the sensor to the 3.3V pin of the Raspberry Pi, pin 2 to GPIO18, and pin 4 to GND. This is the final result: Let us now see how to configure the project. Go over to IFTTT and create add the Email Channel to your account: After that, create a new recipe by choosing the Maker channel as the trigger: For the event, enter temperature_alert and then choose Email as the action channel: You will then be able to customize the text and subject of the email sent to Pi. As we want to send the emails whenever the temperature in your home gets too low, you can use a similar message: You can now finalize the creation of the recipe and close IFTTT. Let's now see how to configure the Raspberry Pi Zero. As the code for this project is quite similar to the one we saw in the previous section, I will only highlight the main differences here. It starts by including the required components: var request = require('request'); var sensorLib = require('node-dht-sensor'); Then, give the correct name to the event we'll use in the project: var eventName = 'temperature_low'; We also define the pin on which the sensor is connected: var sensorPin = 18; As we want to send alerts based on the measured temperature, we need to define a threshold. As it was quite warm when I made this project, I have assigned a high threshold at 30 degrees Celsius, but you can, of course, modify it: var threshold = 30; Summary In this article, we learned all the basics about sending automated notifications from your Raspberry Pi. We learned, for example, how to send notifications via email, text messages, and push notifications. This is really important to build a smart home, as you want to be able to get alerts in real-time from what's going on inside your home and also receive regular reports about the current status of your home. Resources for Article: Further resources on this subject: The Raspberry Pi and Raspbian [article] Building Our First Poky Image for the Raspberry Pi [article] Raspberry Pi LED Blueprints [article]

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article-image-preparing-initial-two-nodes

Packt

02 Mar 2017

8 min read

Preparing the Initial Two Nodes

Packt

02 Mar 2017

8 min read

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17012

article-image-raspberry-pi-led-blueprints

Packt

16 Sep 2015

5 min read

Raspberry Pi LED Blueprints

Packt

16 Sep 2015

5 min read

Blinking LEDs is a popular application in the field of embedded development. In Raspberry Pi LED Blueprints by Agus Kurniawan, we are going to design, build, and test LED-based projects using the Raspberry Pi. To Implement real LED-based projects for Raspberry Pi, we need to learn how to interface various LED modules, such as LEDs, 7-segment, 4-digit 7-segment, and dot matrix to Raspberry Pi. We will get hands-on experience by exploring real-time LEDs with this project-based book. (For more resources related to this topic, see here.) Why Raspberry Pi? The Raspberry Pi was designed by the Raspberry Pi Foundation in the UK initially to help schoolkids learn basic computer science knowledge. The Raspberry Pi uses Linux as a basic programming language, and they attempt to come up with their own language that fits this technology better sometime in the future. Although Raspberry Pi is as small as the size of a credit card, it works like a normal computer at a relatively low price. A Raspberry Pi can easily control an LED, which is a simple actuator device that displays lighting. This book will provide you with the ability to control LEDs using Raspberry Pi. What this article covers? This article covers introduction of Raspberry Pi GPIO. In this, we will learn how to use different libraries to access Raspberry Pi GPIO. The step-by-step procedure to install it is also provided along with the Python command. Introducing Raspberry Pi GPIO General-purpose input/output (GPIO) is a generic pin on the Raspberry Pi, which can be used to interact with external devices, for instance, sensor and actuator devices. In general, you can see Raspberry Pi GPIO pinouts in the following figure: To access Raspberry Pi GPIO, we can use several GPIO libraries. If you are working with Python, Raspbian has already installed the RPi.GPIO library to access Raspberry Pi GPIO. You can read more about RPi.GPIO at https://pypi.python.org/pypi/RPi.GPIO. You can verify the RPi.GPIO library from a Python terminal by importing the RPi.GPIO module. If you don’t find this library on Python at runtime or get the error message ImportError: No module named RPi.GPIO, you can install it by compiling from the source code. For instance, if we want to install RPi.GPIO 0.5.11, type the following commands: wget https://pypi.python.org/packages/source/R/RPi.GPIO/RPi.GPIO-0.5.11.tar.gz tar -xvzf RPi.GPIO-0.5.11.tar.gz cd RPi.GPIO-0.5.11/ sudo python setup.py install To install and update through the apt command, your Raspberry Pi must be connected to the Internet. Another way to access Raspberry Pi GPIO is to use WiringPi. It is a library written in C for Raspberry Pi to access GPIO pins. You can read more about WiringPi at http://wiringpi.com/. To install WiringPi, you can type the following commands: sudo apt-get update sudo apt-get install git-core git clone git://git.drogon.net/wiringPi cd wiringPi sudo ./build Please make sure that your Pi network does not block the git protocol for git://git.dragon.net/wiringPi. You can browsed https://git.drogon.net/?p=wiringPi;a=summary for this code. The next step is to install the WiringPi interface for Python, so you can access Raspberry Pi GPIO from the Python program. Type the following commands: sudo apt-get install python-dev python-setuptools git clone https://github.com/Gadgetoid/WiringPi2-Python.git cd WiringPi2-Python sudo python setup.py install When finished, you can verify it by showing GPIO map from the Raspberry Pi board using the following gpio tool: gpio readall You should see the GPIO map from the Raspberry Pi board on the terminal. You can also see values in the wPi column, which will be used in the WirinPi program as GPIO value parameters. In this book, you can find more information about how to use it on the WiringPi library. What you need for this book? We are going to use Raspberry Pi 2 board Model B. To make Raspberry Pi work, we need OS that acts as a bridge between the hardware and the user. There are many OS options that you can use for Raspberry Pi. This book uses Raspbian for the OS platform for Raspberry Pi. To deploy Raspbian on Raspberry Pi 2 Model B, we need microSD card of at least 4 GB size. Who this book is written for? This book is for those who want to learn how to build Raspberry Pi projects using LEDs, 7-segment, 4-digit 7-segment, and dot matrix modules. You will also learn to implement those modules in real applications, including interfacing with wireless modules and the Android mobile app. However, you don't need to have any previous experience with the Raspberry Pi or Android platforms. Summary In this article, we learned different techniques to install Raspberry Pi GPIO. Read Raspberry Pi LED Blueprints to start designing and implementing several projects based on LEDs, such as 7-segments, 4-digit 7-segment, and dot matrix displays. Other related titles are: Raspberry Pi Blueprints Raspberry Pi Super Cluster Learning Raspberry Pi Raspberry Pi Robotic Projects Resources for Article: Further resources on this subject: Color and motion finding [article] Basic Image Processing [article] Develop a Digital Clock [article]

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Packt

02 Feb 2017

11 min read

BLE and the Internet of Things

Packt

02 Feb 2017

11 min read

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15404

Packt

03 Jan 2017

5 min read

Our First Program!

Packt

03 Jan 2017

5 min read

In this article by Syed Omar Faruk Towaha, author of Learning C for Arduino, we will be learning how we can connect our Arduino to our system and we will learn how to write program on the Arduino IDE. (For more resources related to this topic, see here.) First connect your A-B cable to your PC and then connect the cable to the PC. Your PC will make a sound which will confirm that the Arduino has connected to the PC. Now open the Arduino IDE. From menu go to Tools | Board:"Arduino/Genuino Uno". You can select any board you have bought from the list. See the following screenshot for the list: You have to select the port on which the Arduino is connected. There are a lot of things you can do to see on which port your Arduino is connected. Hello Arduino! Let's write our first program on the Arduino IDE. Go to File and click on New. A text editor will open with few lines of code. Delete those lines first, and then type the following code: void setup() { Serial.begin(9600); } void loop() { Serial.print("Hello Arduino!n"); } From menu go to Sketch and click Upload. It is a good practice to verify or compile the code before uploading to the Arduino board. To verify or compile the code you need to go to Sketch and click Verify/Compile. You will see a message Done compiling. on the bottom of the IDE if the code is error free. See the following figure for the explanation: After the successful upload, you need to open the serial monitor of the Arduino IDE. To open the serial monitor, you need to go to Tools and click on Serial Monitor. You will see the following screen: setup() function The setup() function helps to initialize variables, set pin modes, and we can also use libraries here. This function is called first when we compile or upload the whole code. The setup() runs only for the first time it is uploaded to the board and later it runs every time we press the reset button on the Arduino. On our code we used Serial.begin(9600); which sets the data rate per second for the serial communication. We already know that serial communication is the process by which we send data one bit at a time over a communication channel. For Arduino to communicate with the computer we used the data rate 9600 which is a standard data rate. This is also known as baud rate. We can set the baud rate any of the following depending on the connection speed and type. I will recommend using 9600 for general data communication purposes. If you use higher baud rate, the characters we print might be broken: 300 1200 2400 4800 9600 19200 38400 57600 74880 115200 230400 250000 If we do not declare the baud rate inside the setup() function there will be no output on the serial monitor. Baud rate 9600 means 960 characters per second. This is because in serial communication, you need to transmit one start bit, eight data bits and one stop bit, for a total of 10 bits at a speed of 9600 bits per second. loop() function loop() function will let the code run again and again until we disconnect the Arduino. We have written a print statement on the loop() function which will execute for the infinity time. To print something on the serial monitor we need to write the following line: Serial.print("Anything We Want To Print"); Between the quotations we can write anything we want to print. On the last code we have written Serial.print("Hello Arduino!n");. That's why on the serial monitor we have seen Hello Arduino! had been printing for an infinity time. We have used n after Hello Arduino!.This is called escape sequence. For now, just remember we need to put this after each of our line inside the print statement to break a line and print the next command on the net line. We can use Serial.println("Hello Arduino!"); instead of Serial.print("Hello Arduino!n");. Both will give the same result. We need to put Serial.println("Hello Arduino!"); inside the setup() function. Now let's see what happens if we put a print statement inside the setup() function. Have a look at the following figure. Hello Arduino! is printed for only one time: Since C is a case sensitive language we need to be careful about the casing. We cannot use serial.print("Hello Arduino!"); instead of Serial.print("Hello Arduino!n");. Summary In this article we have learned how to connect the Arduino to our system and uploaded the code to our board. We have learned how the Arduino code work. If you are new to Arduino this article is most important. Resources for Article: Further resources on this subject: Zabbix Configuration [article] A Configuration Guide [article] Thorium and Salt API [article]

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Packt

17 Oct 2016

9 min read

First Projects with the ESP8266

Packt

17 Oct 2016

9 min read

In this article by Marco Schwartz, author Internet of Things with ESP8266, we will focus on the ESP8266 chip is ready to be used and you can connect it to your Wi-Fi network, we can now build some basic projects with it. This will help you understand the basics of the ESP8266. (For more resources related to this topic, see here.) We are going to see three projects in this article: how to control an LED, how to read data from a GPIO pin, and how to grab the contents from a web page. We will also see how to read data from a digital sensor. Controlling an LED First, we are going to see how to control a simple LED. Indeed, the GPIO pins of the ESP8266 can be configured to realize many functions: inputs, outputs, PWM outputs, and also SPI or I2C communications. This first project will teach you how to use the GPIO pins of the chip as outputs. The first step is to add an LED to our project. These are the extra components you will need for this project: 5mm LED (https://www.sparkfun.com/products/9590) 330 Ohm resistor (to limit the current in the LED) (https://www.sparkfun.com/products/8377) The next step is to connect the LED with the resistor to the ESP8266 board. To do so, the first thing to do is to place the resistor on the breadboard. Then, place the LED on the breadboard as well, connecting the longest pin of the LED (the anode) to one pin of the resistor. Then, connect the other end of the resistor to the GPIO pin 5 of the ESP8266, and the other end of the LED to the ground. This is how it should look like at the end: We are now going to light up the LED by programming the ESP8266 chip, by connecting it to the Wi-Fi network. This is the complete code for this section: // Import required libraries #include <ESP8266WiFi.h> void setup() { // Set GPIO 5 as output pinMode(5, OUTPUT); // Set GPIO 5 on a HIGH state digitalWrite(5, HIGH); } void loop() { } This code simply sets the GPIO pin as an output, and then applies a HIGH state on it. The HIGH state means that the pin is active, and that positive voltage (3.3V) is applied on the pin. A LOW state would mean that the output is at 0V. You can now copy this code and paste it in the Arduino IDE. Then, upload the code to the board using the instructions from the previous article. You should immediately see that the LED is lighting up. You can shut it down again by using digitalWrite(5, LOW) in the code. You could also, for example, modify the code so the ESP8266 switches the LED on and off every second. Reading data from a GPIO pin As a second project in this article, we are going to read the state of a GPIO pin. For this, we will use the same pin as in the previous project. You can therefore remove the LED and the resistor that we used in the previous project. Now, simply connect this pin (GPIO 5) of the board to the positive power supply on your breadboard with a wire, therefore applying a 3.3V signal on this pin. Reading data from a pin is really simple. This is the complete code for this part: // Import required libraries #include <ESP8266WiFi.h> void setup(void) { // Start Serial (to display results on the Serial monitor) Serial.begin(115200); // Set GPIO 5 as input pinMode(5, INPUT);} void loop() { // Read GPIO 5 and print it on Serial port Serial.print("State of GPIO 5: "); Serial.println(digitalRead(5)); // Wait 1 second delay(1000); } We simply set the pin as an input, and then read the value of this pin, and print it out every second. Copy and paste this code into the Arduino IDE, then upload it to the board using the instructions from the previous article. This is the result you should get in the Serial monitor: State of GPIO 5: 1 We can see that the returned value is 1 (digital state HIGH), which is what we expected, because we connected the pin to the positive power supply. As a test, you can also connect the pin to the ground, and the state should go to 0. Grabbing the content from a web page As a last project in this article, we are finally going to use the Wi-Fi connection of the chip to grab the content of a page. We will simply use the www.example.com page, as it's a basic page largely used for test purposes. This is the complete code for this project: // Import required libraries #include <ESP8266WiFi.h> // WiFi parameters constchar* ssid = "your_wifi_network"; constchar* password = "your_wifi_password"; // Host constchar* host = "www.example.com"; void setup() { // Start Serial Serial.begin(115200); // We start by connecting to a WiFi network Serial.println(); Serial.println(); Serial.print("Connecting to "); Serial.println(ssid); WiFi.begin(ssid, password); while (WiFi.status() != WL_CONNECTED) { delay(500); Serial.print("."); } Serial.println(""); Serial.println("WiFi connected"); Serial.println("IP address: "); Serial.println(WiFi.localIP()); } int value = 0; void loop() { Serial.print("Connecting to "); Serial.println(host); // Use WiFiClient class to create TCP connections WiFiClient client; const int httpPort = 80; if (!client.connect(host, httpPort)) { Serial.println("connection failed"); return; } // This will send the request to the server client.print(String("GET /") + " HTTP/1.1rn" + "Host: " + host + "rn" + "Connection: closernrn"); delay(10); // Read all the lines of the reply from server and print them to Serial while(client.available()){ String line = client.readStringUntil('r'); Serial.print(line); } Serial.println(); Serial.println("closing connection"); delay(5000); } The code is really basic: we first open a connection to the example.com website, and then send a GET request to grab the content of the page. Using the while(client.available()) code, we also listen for incoming data, and print it all inside the Serial monitor. You can now copy this code and paste it into the Arduino IDE. This is what you should see in the Serial monitor: This is basically the content of the page, in pure HTML code. Reading data from a digital sensor In this last section of this article, we are going to connect a digital sensor to our ESP8266 chip, and read data from it. As an example, we will use a DHT11 sensor that can be used to get ambient temperature and humidity. You will need to get this component for this section, the DHT11 sensor (https://www.adafruit.com/products/386) Let's now connect this sensor to your ESP8266: First, place the sensor on the breadboard. Then, connect the first pin of the sensor to VCC, the second pin to pin #5 of the ESP8266, and the fourth pin of the sensor to GND. This is how it will look like at the end: Note that here I've used another ESP8266 board, the Adafruit ESP8266 breakout board. We will also use the aREST framework in this example, so it's easy for you to access the measurements remotely. aREST is a complete framework to control your ESP8266 boards remotely (including from the cloud), and we are going to use it several times in the article. You can find more information about it at the following URL: http://arest.io/. Let's now configure the board. The code is too long to be inserted here, but I will detail the most important part of it now. It starts by including the required libraries: #include "ESP8266WiFi.h" #include <aREST.h> #include "DHT.h" To install those libraries, simply look for them inside the Arduino IDE library manager. Next, we need to set the pin on which the DHT sensor is connected to: #define DHTPIN 5 #define DHTTYPE DHT11 After that we declare an instance of the DHT sensor: DHT dht(DHTPIN, DHTTYPE, 15); As earlier, you will need to insert your own Wi-Fi name and password inside the code: const char* ssid = "wifi-name"; const char* password = "wifi-pass"; We also define two variables that will hold the measurements of the sensor: float temperature; float humidity; In the setup() function of the sketch, we initialize the sensor: dht.begin(); Still in the setup() function, we expose the variables to the aREST API, so we can access them remotely via Wi-Fi: rest.variable("temperature",&temperature); rest.variable("humidity",&humidity); Finally, in the loop() function, we make the measurements from the sensor: humidity = dht.readHumidity(); temperature = dht.readTemperature(); It's now time to test the project! Simply grab all the code and put it inside the Arduino IDE. Also make sure to install the aREST Arduino library using the Arduino library manager. Now, put the ESP8266 board in bootloader mode, and upload the code to the board. After that, reset the board, and open the Serial monitor. You should see the IP address of the board being displayed: Now, we can access the measurements from the sensor remotely. Simply go to your favorite web browser, and type: 192.168.115.105/temperature You should immediately get the answer from the board, with the temperature being displayed: { "temperature": 25.00, "id": "1", "name": "esp8266", "connected": true } You can of course do the same with humidity. Note that we used here the aREST API. You can learn more about it at: http://arest.io/. Congratulations, you just completed your very first projects using the ESP8266 chip! Feel free to experiment with what you learned in this article, and start learning more about how to configure your ESP8266 chip. Summary In this article, we realized our first basic projects using the ESP8266 Wi-Fi chip. We first learned how to control a simple output, by controlling the state of an LED. Then, we saw how to read the state of a digital pin on the chip. Finally, we learned how to read data from a digital sensor, and actually grab this data using the aREST framework. We are going to go right into the main topic of the article, and build our first Internet of Things project using the ESP8266. Resources for Article: Further resources on this subject: Sending Notifications using Raspberry Pi Zero [article] The Raspberry Pi and Raspbian [article] Working with LED Lamps [article]

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14940

Packt

12 May 2016

11 min read

Working with LED Lamps

Packt

12 May 2016

11 min read

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14756

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