Raspberry Pi for Python Programmers Cookbook - Second Edition

The Raspberry Pi is a single-board computer created by the Raspberry Pi Foundation, a charity formed with the primary purpose of reintroducing low-level computer skills to children in the UK. The aim was to rekindle the microcomputer revolution of the 1980s, which produced a whole generation of skilled programmers.

Even before the computer was released at the end of February 2012, it was clear that the Raspberry Pi had gained a huge following worldwide and, at the time of writing this book, has sold over 10 million units. The following image shows several different Raspberry Pi Models:

Raspberry Pi Model 3B, Model A+, and Pi Zero

The name, Raspberry Pi, was the combination of the desire to create an alternative fruit-based computer (such as Apple, BlackBerry, and Apricot) and a nod to the original concept of a simple computer that can be programmed using Python (shortened to Pi).

In this book, we will take this little computer, find out how to set it up, and then explore its capabilities chapter by chapter using the Python programming language.

It is often asked, "Why has Python been selected as the language to use on the Raspberry Pi?" The fact is that Python is just one of the many programming languages that can be used on the Raspberry Pi.

There are many programming languages that you can choose, from high-level graphical block programming, such as Scratch, to traditional C, right down to BASIC, and even raw Machine Code Assembler. A good programmer often has to be code multilingual to be able to play to the strengths and weaknesses of each language in order to best meet the needs of their desired application. It is useful to understand how different languages (and programming techniques) try to overcome the challenge of converting "what you want" into "what you get" as this is what you are trying to do as well while you program.

Python has been selected as a good place to start when learning about programming, by providing a rich set of coding tools while still allowing simple programs to be written without fuss. This allows beginners to gradually be introduced to the concepts and methods on which modern programming languages are based without requiring them to know it all from the start. It is very modular with lots of additional libraries that can be imported to quickly extend the functionality. You will find that over time, this encourages you to do the same, and you will want to create your own modules that you can plug into your own programs, thus taking your first steps into structured programming.

Like all programming languages, Python isn't perfect; things such as adding a space at the start of a line will often break your code (indents matter a lot in Python; they define how blocks of code are grouped together). Generally, Python is slow; since it is interpreted, it takes time to create a module while it is running the program. This can be a problem if you need to respond to time critical events. However, you can precompile Python or use modules written in other languages to overcome this. It hides the details; this is both an advantage and disadvantage. It is excellent for beginners but can be difficult when you have to second-guess aspects such as data-types. However, this in turn forces you to consider all the possibilities, which can be a good thing.

A massive source of confusion for beginners is that there are two versions of Python on the Raspberry Pi (Version 2.7 and Version 3.4), which are not compatible with one another, so code written for Python 2.7 may not run with Python 3.4 (and vice versa).

The Python Software Foundation is continuously working to improve and move forward with the language, which sometimes means they have to sacrifice backward compatibility in order to embrace new improvements (and importantly, remove redundant and legacy ways of doing things).

Essentially, the selection of which version to use will depend on what you intend to do. For instance, you may require Python 2.7 libraries, which are not yet available for Python 3.4. Python 3 has been available since 2008, so these tend to be older or larger libraries that have not been translated. In many cases, there are new alternatives to legacy libraries; however, their support can vary.

In this book, we have used Python 3.4, which is also compatible with Python 3.3 and 3.2.

Since its release, the Raspberry Pi has come in various iterations, featuring both small and large updates and improvements to the original Raspberry Pi Model B unit. Although it can be confusing at first, there are three basic types of Raspberry Pi available (and one special model).

The main flagship model is called Model B . This has all the connections and features, as well as the maximum RAM and the latest processor. Over the years, there have been several versions, most notably Model B (which had 256 MB and then 512 MB RAM) and then Model B+ (which increased the 26-pin GPIO to 40 pins, switched to using a micro SD card slot, and had four USB ports instead of two). These original models all used the Broadcom BCM2835 SOC (short for System On Chip), consisting of a single core 700 MHz ARM11 and VideoCore IV GPU (short for Graphical Processing Unit).

The release of the Raspberry Pi 2 Model B (also referred to as 2B) in 2015 introduced a new Broadcom BCM2836 SOC, providing a quad-core 32-bit ARM Cortex A7 1.2 GHz processor and GPU, with 1 GB of RAM. The improved SOC added support for Ubuntu and Windows 10 IoT. Finally we had the latest Raspberry Pi 3 Model B, using another new Broadcom BCM2837 SOC, which provides a quad-core 64-bit ARM Cortex-A53 and GPU, alongside adding on-board Wi-Fi and Bluetooth.

Model A has always been targeted as a cut-down version. While having the same SOC as Model B, there are limited connections consisting of a single USB port and no wired network (LAN). Model A+ again added more GPIO pins and a micro SD slot. However, the RAM was later upgraded to 512 MB of RAM and again only a single USB port/no LAN. The Broadcom BCM2835 SOC on Model A has not been updated so far (so is still a single core ARM11); however, a Model 3A (most likely using the BCM2837) is expected 2016/2017.

The Pi Zero is an ultra-compact version of the Raspberry Pi intended for embedded applications where cost and space are a premium. It has the same 40-pin GPIO and micro SD card slot as the other models, but lacks the on-board display (CSI and DSI) connection. It does still have HDMI (via a mini-HDMI) and a single micro USB OTG (on-the-go) connection. Although not present in the first revision of the Pi Zero, the most recent model also includes a CSI connection for the on-board camera.

The special model is known as the compute module. This takes the form of a 200-pin SO-DIMM card. It is intended for industrial use or within commercial products, where all the external interfaces would be provided by a host/motherboard, into which the module would be inserted. Example products include the Slice media player (http://fiveninjas.com) and the Otto camera. The current module uses the BCM2835, although an updated compute module (CM3) is expected in 2016.

The Raspberry Pi Wikipedia page provides a full list of the all different variants and their specifications:

https://en.wikipedia.org/wiki/Raspberry_Pi#Specifications

All sections of this book are compatible will all current versions of the Raspberry Pi, but Model 3B is recommended as the best model to start with. This offers the best performance (particularly useful for the GPU examples in Chapter 5, Creating 3D Graphics, and the OpenCV examples used in Chapter 8, Creating Projects with the Raspberry Pi Camera Module), lots of connections, and built-in Wi-Fi, which can be very convenient.

The Pi Zero is recommended for projects where you want low power usage or reduced weight/size but do not need the full processing power of Model 3B. However, due to its ultra-low cost, the Pi Zero is ideal for deploying a completed project after you have developed it.

Before you can use your Raspberry Pi, you will need an SD card with an operating system installed or with the New Out Of Box System (NOOBS) on it, as discussed in the Using NOOBS to set up your Raspberry Pi SD card recipe.

The following section will detail the types of devices you can connect to the Raspberry Pi and, importantly, how and where to plug them in.

As you will discover later, once you have your Raspberry Pi set up, you may decide to connect remotely and use it through a network link, in which case you only need power and a network connection. Refer to the following sections: Connecting remotely to the Raspberry Pi over the network using VNC and Connecting remotely to the Raspberry Pi over the network using SSH (and X11 Forwarding).

The layout of the Raspberry Pi is shown in the following figure:

The Raspberry Pi connection layout (Model 3 B, Model A+, and Pi Zero)

The description of the preceding figure is as follows:

You should aim to make all other connections to the Raspberry Pi before connecting the power. However, USB devices, audio, and network may be connected and removed while it is running without problems.

In addition to the standard primary connections you would expect to see on a computer, the Raspberry Pi also has a number of other connections.

Since NOOBS creates a RECOVERY partition to keep the original installation images, an 8-GB SD card or larger is recommended. You will also need an SD card reader (experience has shown that some built-in card readers can cause issues, so an external USB type reader is recommended).

If you are using an SD card that you have used previously, you may need to reformat it to remove any previous partitions and data. NOOBS expects the SD card to consist of a single FAT32 partition. If using Windows or Mac OS X, you can use the SD association's formatter, as shown in the following screenshot (available at https://www.sdcard.org/downloads/formatter_4/):

Get rid of any partitions on the SD card using SD formatter

From the Option Setting dialog box, set Format Size Adjustment. This will remove all the SD card partitions that were created previously.

If using Linux, you can use gparted to clear any previous partitions and reformat it as a FAT32 partition.

The full NOOBS package (typically just over 1 GB) contains the Raspbian, the most popular Raspberry Pi operating system image built in. A lite version of NOOBS is also available that has no preloaded operating systems (although a smaller initial download of 20 MB and a network connection on the Raspberry Pi are required to directly download the operating system you intend to use).

NOOBS is available at http://www.raspberrypi.org/downloads, with the documentation available at https://github.com/raspberrypi/noobs.

By performing the following steps, we will prepare the SD card to run NOOBS. This will then allow us to select and install the operating system we want to use:

By default, NOOBS will display via the HDMI connection. If you have another type of screen (or you don't see anything), you will need to manually select the output type by pressing 1, 2, 3, or 4 according to the following functions:

This display setting will also be set for the installed operating system.

After a short while, you will see the NOOBS selection screen that lists the available distributions (the offline version only includes Raspbian). There are many more distributions that are available, but only the selected ones are available directly through the NOOBS system. Click on Raspbian as this is the operating system being used in this book.

Press Enter or click on Install OS, and confirm that you wish to overwrite all the data on the card. This will overwrite any distributions previously installed using NOOBS but will not remove the NOOBS system; you can return to it at any time by pressing Shift when you turn the power on.

It will take around 20 to 40 minutes to write the data to the card depending on its speed. When it completes and the Image Applied Successfully message appears, click on OK and the Raspberry Pi will start to boot into the Raspberry Pi Desktop.

The purpose of writing the image file to the SD card in this manner is to ensure that the SD card is formatted with the expected filesystem partitions and files required to correctly boot the operating system.

When the Raspberry Pi powers up, it loads some special code contained within the GPU's internal memory (commonly referred to as binary blob by the Raspberry Pi Foundation). The binary blob provides the instructions required to read the BOOT Partition on the SD card, which (in the case of a NOOBS install) will load NOOBS from the RECOVERY partition. If at this point Shift is pressed, NOOBS will load the recovery and installation menu. Otherwise, NOOBS will begin loading the OS as specified by the preferences stored in the SETTINGS Partition.

When loading the operating system, it will boot via the BOOT partition using the settings defined in config.txt and options in cmdline.txt to finally load to the desktop on the root Partition. Refer to the following diagram:

NOOBS creates several partitions on the SD card to allow installation of multiple operating systems and provide recovery

NOOBS allows the user to optionally install multiple operating systems on the same card and provides a boot menu to select between them (with an option to set a default value in the event of a time-out period).

If you later add, remove, or reinstall an operating system, ensure first that you make a copy of any files, including system settings you wish to keep, as NOOBS may overwrite everything on the SD card.

When you power up the Raspberry Pi for the first time, it will start directly with the desktop. You can now configure the system settings using the Raspberry Pi Configuration program (under the Preferences menu on the Desktop or via the sudo raspi-config command), which will allow you to perform changes to your SD card and set up your general preferences.

Raspberry Pi Configuration program

Changing the default user password

Ensure that you change the default password for the pi user account once you have logged in, as the default password is well known. This is particularly important if you connect to public networks. You can do this with the passwd command, as shown in the following screenshot:

Setting a new password for the pi user

This gives greater confidence because if you later connect to another network, only you will be able to access your files and take control of your Raspberry Pi.

sudo shutdown –h now

sudo halt

sudo reboot

Expanding the system to fit in your SD card

A manually written image will be of a fixed size (usually made to fit the smallest-sized SD card possible). To make full use of the SD card, you will need to expand the system partition to fill the remainder of the SD card. This can be achieved using the Raspberry Pi Configuration tool.

Select Expand Filesystem, as shown in the following screenshot:

The Raspberry Pi Configuration tool

Accessing the RECOVERY/BOOT partition

Windows and Mac OS X do not support the ext4 format, so when you read the SD card, only the File Allocation Table (FAT) partitions will be accessible. In addition, Windows only supports the first partition on an SD card, so if you've installed NOOBS, only the RECOVERY partition will be visible. If you've written your card manually, you will be able to access the BOOT partition.

The data partition (if you installed one via NOOBS) and the root partition are in ext4 format and won't usually be visible on non-Linux systems.

Note

If you do need to read files from the SD card using Windows, a freeware program, Linux Reader (available at www.diskinternals.com/linux-reader) can provide read-only access to all of the partitions on the SD card.

Access the partitions from the Raspberry Pi. To view the currently mounted partitions, use df, as shown in the following screenshot:

The result of the df command

To access the BOOT partition from within Raspbian, use the following command:

cd /boot/

To access the RECOVERY or data partition, we have to mount it by performing the following steps:

1. Determine the name of the partition as the system refers to it by listing all the partitions, even the unmounted ones. The sudo fdisk -l command lists the partitions, as shown in the following screenshot:

   

   The partition table of a NOOBS install of Raspbian and data partition

   mmcblk0p1	(vfat) RECOVERY
   mmcblk0p2	(Extended partition) contains (root, data, BOOT)
   mmcblk0p5	(ext4) root
   mmcblk0p6	(vfat) BOOT
   mmcblk0p7	(ext4) SETTINGS

   If you have installed additional operating systems on the same card, the partition identifiers shown in the preceding table will be different.

2. Create a folder and set it as the mount point for the partition, as follows:

   • For the RECOVERY partition, use the following command:

     mkdir ~/recovery
     sudo mount –t vfat /dev/mmcblk0p1 ~/recovery
     

To ensure that they are mounted each time the system is started, perform the following steps:

1. Add the sudo mount commands to /etc/rc.local before exit 0. If you have a different username, you will need to change pi to match:

   sudo nano /etc/rc.local
   sudo mount -t vfat /dev/mmcblk0p1 /home/pi/recovery
   

2. Save and exit by pressing Ctrl + X, Y, and Enter.

Note

Commands added to /etc/rc.local will be run for any user who logs on to the Raspberry Pi. If you only want the drive to be mounted for the current user, the commands can be added to .bash_profile instead.

If you have to install additional operating systems on the same card, the partition identifiers shown here will be different.

Using the tools to back up your SD card in case of failure

You can use Win32 Disk Imager to make a full backup image of your SD card by inserting your SD card into your reader, starting the program, and creating a filename to store the image in. Simply click on the Read button instead to read the image from the SD card and write it to a new image file.

To make a backup of your system, or to clone to another SD card using the Raspberry Pi, use the SD Card Copier (available from the desktop menu via the Accessories | SD Card Copier).

Insert an SD card into a card reader into a spare USB port of the Raspberry Pi and select the new storage device, as shown in the following screenshot:

SD Card Copier program

Before continuing, the SD Card Copier will confirm that you wish to format and overwrite the target device and, if there is sufficient space, make a clone of your system.

The dd command can similarly be used to back up the card, as follows:

• For Linux, replacing sdX with your device ID, use this command:

  sudo dd if=/dev/sdX of=image.img.gz bs=1M
  

• For OS X, replacing diskX with your device ID, use the following command:

  sudo dd if=/dev/diskX of=image.img.gz bs=1M
  

• You can also use gzip and split to compress the contents of the card and split them into multiple files if required for easy archiving, as follows:

  sudo dd if=/dev/sdX bs=1M | gzip –c | split –d –b 2000m – image.img.gz
  

• To restore the split image, use the following command:

  sudo cat image.img.gz* | gzip –dc | dd of=/dev/sdX bs=1M
  

You will need access to a suitable wired network, which will be connected to the Internet, and a standard network cable (with an RJ45 type connector for connecting to the Raspberry Pi).

Many networks connect and configure themselves automatically using Dynamic Host Configuration Protocol (DHCP), which is controlled by the router or switch. If this is the case, simply plug the network cable into a spare network port on your router or network switch (or wall network socket if applicable).

Alternatively, if a DHCP server is not available, you shall have to configure the settings manually (refer to the There's more… section for details).

You can confirm this is functioning successfully with the following steps:

If the aforementioned tests fail, you will need to check your connections and then confirm the correct configuration for your network.

If you find yourself using your Raspberry Pi regularly on the network, you won't want to have to look up the IP address each time you want to connect to it.

On some networks, you may be able to use the Raspberry Pi's hostname instead of its IP address (the default is raspberrypi). To assist with this, you may need some additional software such as Bonjour to ensure hostnames on the network are correctly registered. If you have an OS X Mac, you will have Bonjour running already. On Windows, you can either install iTunes (if you haven't got it) which also includes the service, or you can install it separately (via the Apple Bonjour Installer available from https://support.apple.com/kb/DL999). Then you can use the hostname, raspberrypi or raspberrypi.local, to connect to the Raspberry Pi over the network. If you need to change the hostname, then you can do so in the Raspberry Pi configuration tool, shown previously.

Alternatively, you may find it helpful to fix the IP address to a known value by manually setting the IP address. However, remember to switch it back to use DHCP when connecting on another network.

Some routers will also have an option to set a Static IP DHCP address, so the same address is always given to the Raspberry Pi (how this is set will vary on the router itself).

Knowing your Raspberry Pi's IP address or using the hostname is particularly useful if you intend to use one of the remote access solutions described later on, which avoids the need for a display.

The latest version of Raspbian includes helpful utilities to quickly and easily configure your Wi-Fi and Bluetooth through the graphical interface.

Wi-Fi and Bluetooth configuration applications

You can use the built-in Bluetooth to connect a wireless keyboard, a mouse or even wireless speakers. This can be exceptionally helpful for projects where additional cables and wires are an issue, such as robotic projects, or when the Raspberry Pi is installed in hard-to-reach locations (acting as a server or security camera).

Before you start, you will need to determine the network settings for your network.

You will need to find out the following information from your router's settings or another computer connected to the network:

For Windows, you can obtain this information by connecting to the Internet and running the following command:

ipconfig /all

Locate the active connection (usually called Local Area Connection 1 or similar if you are using a wired connection, or if you are using Wi-Fi, it is called wireless network connection) and find the information required, as follows:

The ipconfig/all command shows useful information about your network settings

For Linux and Mac OS X, you can obtain the required information with the following command (note that it is ifconfig rather than ipconfig):

ifconfig

The DNS servers are called nameservers and are usually listed in the resolv.conf file. You can use the less command as follows to view its contents (press Q to quit when you have finished viewing it):

less /etc/resolv.conf

To set the network interface settings, edit /etc/network/interfaces using the following code:

sudo nano /etc/network/interfaces

Now, perform the following steps:

You can configure the network settings by editing cmdline.txt in the BOOT partition and adding settings to the startup command line with ip.

The ip option takes the following form:

ip=client-ip:nfsserver-ip:gw-ip:netmask:hostname:device:autoconf

You will need the Raspberry Pi with power and a standard network cable.

It may also be helpful to have a keyboard and monitor available to perform additional testing, particularly if this is the first time you have tried this.

To ensure that you can restore your network settings to their original values, you should check whether it has a fixed IP address or the network is configured automatically.

To check the network settings on Windows 10, perform these steps:

To check the network settings on Windows 7 and Vista, perform the following steps:

To check the network settings on Linux, perform the following steps:

To check the network settings on Mac OS X, perform the following steps:

If you just need to access or control the Raspberry Pi without an Internet connection, refer to the Direct network link section in the There's more…section.

First, we need to enable ICS on our network devices. In this case, we will be sharing the Internet, which is available on Wireless Network Connection through the Ethernet connection to the Raspberry Pi.

For Windows, perform these steps:

For Mac OS X, to enable the ICS, perform the following steps:

For Linux to enable the ICS, perform the following steps:

The IP address of the network adapter will be the Gateway IP address to be used on the Raspberry Pi, and be assigned an IP address within the same range (matching except the last number). For instance, if the computer's wired connection now has 192.168.137.1, the Gateway IP of the Raspberry Pi will be 192.168.137.1 and its own IP address might be set to 192.168.137.10.

Fortunately, thanks to updates in the operating system, Raspbian will now automatically allocate a suitable IP address to join the network and set the gateway appropriately. However, unless we have a screen attached to the Raspberry Pi or scan for devices on our network, we do not know what IP address the Raspberry PI has given itself.

Fortunately (as mentioned in the Networking and connecting your Raspberry Pi to the Internet via the LAN connector recipe in the There's more… section), Apple's Bonjour software will automatically ensure hostnames on the network are correctly registered. As stated previously, if you have an OSX Mac you will have Bonjour running already. On Windows you can either install iTunes, or you can install it separately (available from https://support.apple.com/kb/DL999). By default, the hostname raspberrypi can be used.

We are now ready to test the new connection, as follows:

Hopefully, you will find you have a working connection and receive replies from theRaspberry Pi.

If you have a keyboard and screen connected to the Raspberry Pi, you can perform the following steps:

If all goes well, you will have full Internet available through your computer to the Raspberry Pi, allowing you to browse the web as well as update and install new software.

If the connection fails, perform the following steps:

When we enable ICS on the primary computer, the operating system will automatically allocate a new IP address to the computer. Once connected and powered up, the Raspberry Pi will set itself to a compatible IP address and use the primary computer IP address as an Internet Gateway.

By using Apple Bonjour, we are able to use the raspberrypi hostname to connect to the Raspberry Pi from the connected computer.

Finally, we check whether the computer can communicate over the direct network link to the Raspberry Pi, back the other way, and also through to the Internet.

If you do not require the Internet on the Raspberry Pi, or your computer only has a single network adapter, we can still connect the computers together through a direct network link. Refer to the following diagram:

Connecting and using the Raspberry Pi with just a network cable, a standard imaged SD card, and power

If you don't have a keyboard or screen connected to the Raspberry Pi, you can use this network link to remotely access the Raspberry Pi just as you would on a normal network (just use the new IP address you have set for the connection). Refer to the Connecting remotely to the Raspberry Pi over the network using VNC and Connecting remotely to the Raspberry Pi over the network using SSH (and X11 Forwarding) recipes.

There is lots of additional information available on my website, https://pihw.wordpress.com/guides/direct-network-connection, including additional troubleshooting tips and several other ways to connect to your Raspberry Pi without needing a dedicated screen and keyboard.

You will need to obtain a suitable USB Wi-Fi dongle; and in some cases, you may require a powered USB hub (this will depend on the hardware version of the Raspberry Pi you have and the quality of your power supply). General suitability of USB Wi-Fi dongles will vary depending on the chipset that is used inside and the level of Linux support available. You may find that some USB Wi-Fi dongles will work without installing additional drivers (in which case you can jump to configuring it for the wireless network).

A list of supported Wi-Fi adapters is available at http://elinux.org/RPi_USB_Wi-Fi_Adapters.

You will need to ensure that your Wi-Fi adapter is also compatible with your intended network; for example, it supports the same types of signals 802.11bgn and the encryptions WEP, WPA, and WPA2 (although most networks are backward compatible).

You will also need the following details of your network:

You will require a working internet connection (that is, wired Ethernet) in order to download the required drivers. Otherwise, you may be able to locate the required firmware files (they will be the .deb files), and copy them to the Raspberry Pi (that is, via a USB flash drive; the drive should be automatically mounted if you are running in desktop mode). Copy the file to a suitable location and install it with the following command:

sudo apt-get install firmware_file.deb

This task has two stages; first, we identify and install firmware for the Wi-Fi adapter, and then we need to configure it for the wireless network.

We will try to identify the chipset of your Wi-Fi adapter (the part that handles the connection); this may not match the actual manufacturer of the device.

An approximate list of supported firmware can be found with this command:

sudo apt-cache search wireless firmware

This will produce results similar to the following output (disregarding any results without firmware in the package title):

atmel-firmware - Firmware for Atmel at76c50x wireless networking chips.
firmware-atheros - Binary firmware for Atheros wireless cards
firmware-brcm80211 - Binary firmware for Broadcom 802.11 wireless cards
firmware-ipw2x00 - Binary firmware for Intel Pro Wireless 2100, 2200 and 2915
firmware-iwlwifi - Binary firmware for Intel PRO/Wireless 3945 and 802.11n cards
firmware-libertas - Binary firmware for Marvell Libertas 8xxx wireless cards
firmware-ralink - Binary firmware for Ralink wireless cards
firmware-realtek - Binary firmware for Realtek wired and wireless network adapters
libertas-firmware - Firmware for Marvell's libertas wireless chip series (dummy package)
zd1211-firmware - Firmware images for the zd1211rw wireless driver

To find out the chipset of your wireless adapter, plug the Wi-Fi-adapter into Raspberry Pi, and from the terminal, run the following command:

dmesg | grep 'Product:\|Manufacturer:'

This should return something similar to the following output (in this case, I've got a ZyXEL device, which has a ZyDAS chipset (a quick Google search reveals that zd1211-firmware is for ZyDAS devices):

[    1.893367] usb usb1: Product: DWC OTG Controller
[    1.900217] usb usb1: Manufacturer: Linux 3.6.11+ dwc_otg_hcd
[    3.348259] usb 1-1.2: Product: ZyXEL G-202
[    3.355062] usb 1-1.2: Manufacturer: ZyDAS

Once you have identified your device and the correct firmware, you can install it, as you would for any other package available through apt-get (where zd1211-firmware can be replaced with your required firmware). This is shown in the following command:

sudo apt-get install zd1211-firmware

Remove and reinsert the USB Wi-Fi dongle to allow it to be detected and the drivers loaded. We can now test if the new adapter is correctly installed with ifconfig. The output is shown as follows:

wlan0     IEEE 802.11bg  ESSID:off/any
          Mode:Managed  Access Point: Not-Associated   Tx-Power=20 dBm
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Power Management:off

The command will show the network adapters present on the system. For Wi-Fi, this is usually as wlan0, or wlan1, or so on if you have installed more than one. If not, double-check the selected firmware, and perhaps try an alternative or check on the site for troubleshooting tips.

Once we have the firmware installed for the Wi-Fi adapter, we will need to configure it for the network we wish to connect. We can use the GUI as shown in the previous recipe, or we can manually configure it through the terminal as shown in the following steps:

The Model A version of the Raspberry Pi does not have a built-in network port; so in order to get a network connection, a USB network adapter will have to be added (either a Wi-Fi dongle, as explained in the preceding section, or a LAN-to-USB adapter, as described in the following section).

sudo apt-get install firmware_file.deb

You will need the address of the proxy server you are trying to connect to, including the username and password if one is required.

You should confirm that the Raspberry Pi is already connected to the network and that you can access the proxy server.

Use the ping command to check this as follows:

ping proxy.address.com -c 4

If this fails (you get no responses), you will need to ensure your network settings are correct before continuing.

Create a new file using nano as follows (if there is already some content in the file, you can add the code at the end):

sudo nano -c ~/.bash_profile

To allow basic web browsing through programs such as midori while using a proxy server, you can use the following script:

function proxyenable {
# Define proxy settings
PROXY_ADDR="proxy.address.com:port"
# Login name (leave blank if not required):
LOGIN_USER="login_name"
# Login Password (leave blank to prompt):
LOGIN_PWD=
#If login specified - check for password
if [[ -z $LOGIN_USER ]]; then
  #No login for proxy
  PROXY_FULL=$PROXY_ADDR
else
  #Login needed for proxy Prompt for password -s option hides input
  if [[ -z $LOGIN_PWD ]]; then
    read -s -p "Provide proxy password (then Enter):" LOGIN_PWD
    echo
  fi
  PROXY_FULL=$LOGIN_USER:$LOGIN_PWD@$PROXY_ADDR
fi
#Web Proxy Enable: http_proxy or HTTP_PROXY environment variables
export http_proxy="http://$PROXY_FULL/"
export HTTP_PROXY=$http_proxy
export https_proxy="https://$PROXY_FULL/"
export HTTPS_PROXY=$https_proxy
export ftp_proxy="ftp://$PROXY_FULL/"
export FTP_PROXY=$ftp_proxy
#Set proxy for apt-get
sudo cat <<EOF | sudo tee /etc/apt/apt.conf.d/80proxy > /dev/null
Acquire::http::proxy "http://$PROXY_FULL/";
Acquire::ftp::proxy "ftp://$PROXY_FULL/";
Acquire::https::proxy "https://$PROXY_FULL/";
EOF
#Remove info no longer needed from environment
unset LOGIN_USER LOGIN_PWD PROXY_ADDR PROXY_FULL
echo Proxy Enabled
}

function proxydisable {
#Disable proxy values, apt-get and git settings
unset http_proxy HTTP_PROXY https_proxy HTTPS_PROXY
unset ftp_proxy FTP_PROXY
sudo rm /etc/apt/apt.conf.d/80proxy
echo Proxy Disabled
}

Once done, save and exit by pressing Ctrl + X, Y, and Enter.

Many programs that make use of the Internet will check for the http_proxy or HTTP_PROXY environment variables before connecting. If they are present, they will use the proxy settings to connect through. Some programs may also use the HTTPS and FTP protocols, so we can set the proxy setting for them here too.

The last part allows any programs that execute using the sudo command to use the proxy environment variables while acting as the super user (most programs will try accessing the network using normal privileges first, even if running as a super user, so it isn't always needed).

We also need to allow the proxy settings to be used by some programs, which use super user permissions while accessing the network (this will depend on the program; most don't need this). We need to add the commands into a file stored in /etc/sudoers.d/ by performing the following steps:

Ensure that your Raspberry Pi is powered up and connected to the Internet. We will use the Internet connection to install a program using apt-get. This is a program that allows us to find and install applications directly from the official repositories.

First, we need to install the TightVNC server on the Raspberry Pi with the following commands. It is advisable to run an update command first to get the latest version of the package you want to install as follows:

sudo apt-get update
sudo apt-get install tightvncserver

Accept the prompt to install and wait until it completes. To start a session, use the following command to start a session:

vncserver :1

The first time you run this, it will ask you to enter a password (of no more than eight characters) to access the desktop (you will use this when you connect from your computer).

The following message should confirm that a new desktop session has been started:

New 'X' desktop is raspberrypi:1

If you do not already know the IP address of the Raspberry Pi, use hostname –I and take note of it.

Next, we need to run a VNC client, VNC Viewer is suitable program, which is available at http://www.realvnc.com/ and should work on Windows, Linux, and OS X.

When you run VNC Viewer, you will be prompted for the Server address and Encryption type. Use the IP address of your Raspberry Pi with :1. That is, for the IP address 192.168.1.69, use the 192.168.1.69:1 address.

You can leave the Encryption type as Off or Automatic.

Depending on your network, you may be able to use the hostname; the default is raspberrypi, that is raspberrypi:1.

You may have a warning about not having connected to the computer before or having no encryption. You should enable encryption if you are using a public network or if you are performing connections over the Internet (to stop others from being able to intercept your data).

You can add options to the command line to specify the resolution and also the color depth of the display. The higher the resolution and color depth (can be adjusted to use 8 to 32 bits per pixel to provide low or high color detail), the more data has to be transferred through the network link. If you find the refresh rate a little slow, try reducing these numbers as follows:

vncserver :1 –geometry 1280x780 –depth 24

To allow the VNC server to start automatically when you switch on, you can add the vncserver command to .bash_profile (this is executed each time the Raspberry Pi starts).

Use the nano editor as follows (the -c option allows the line numbers to be displayed):

sudo nano -c ~/.bash_profile

Add the following line to the end of the file:

vncserver :1

The next time you power up, you should be able to remotely connect using VNC from another computer.

If you are running the latest version of Raspbian, SSH and X11 Forwarding will be enabled by default (otherwise, double-check the settings explained in the How it works… section).

Linux and OS X have built-in support for X11 Forwarding; but if you are using Windows, you will need to install and run the X Windows server on your computer.

Download and run xming from the Xming site (http://sourceforge.net/projects/xming/).

Install xming, following the installation steps, including the installation of PuTTY if you don't have it already. You can also download PuTTY separately from http://www.putty.org/.

Next, we need to ensure that the SSH program we use has X11 enabled when we connect.

For Windows, we shall use PuTTY to connect to the Raspberry Pi.

In the PuTTY Configuration dialog box, navigate to Connection | SSH | X11 and tick the checkbox for X11 Forwarding. If you leave the X display location option blank, it will assume the default Server 0:0 as follows (you can confirm the server number by moving your mouse over the Xming icon in the system tray when it is running):

Enabling X11 Forwarding within the PuTTY configuration

Enter the IP address of the Raspberry Pi in the Session settings (you may also find that you can use the Raspberry Pi's hostname here instead; the default hostname is raspberrypi).

Save the setting using a suitable name, RaspberryPi, and click on Open to connect to your Raspberry Pi.

You are likely to see a warning message pop up stating you haven't connected to the computer before (this allows you to check whether you have everything right before continuing).

Opening an SSH connection to the Raspberry Pi using PuTTY

For OS X or Linux, click on Terminal to open a connection to the Raspberry Pi.

To connect with the default pi username, with an IP address of 192.168.1.69, use the following command; the -X option enables X11 Forwarding:

ssh -X pi@192.168.1.69

All being well, you should be greeted with a prompt for your password (remember the default value for the pi user is raspberry).

Ensure that you have Xming running by starting the Xming program from your computer's Start menu. Then, in the terminal window, type a program that normally runs within the Raspberry Pi desktop, such as leafpad or scratch. Wait a little while and the program should appear on your computer's desktop (if you get an error, you have probably forgotten to start Xming, so run it and try again).

X Windows and X11 is what provides the method by which the Raspberry Pi (and many other Linux-based computers) can display and control graphical Windows as part of a desktop.

For X11 Forwarding to work over a network connection, we need both SSH and X11 Forwarding enabled on the Raspberry Pi. Perform the following steps:

SSH and X 11 Forwarding is a convenient way to control the Raspberry Pi remotely; we will explore some additional tips on how to use it effectively in the following sections.

leafpad &

_tkinter.TclError: couldn't connect to display "localhost:10.0"

sudo cp ~/.Xauthority ~root/

Ensure that you have the Raspberry Pi powered and running with a working connection to the Internet.

You will also need another computer on the same local network to test the new share.

First, we need to install samba, a piece of software that handles folder sharing in a format that is compatible with Windows sharing methods.

Ensure that you use update as follows to obtain the latest list of available packages:

sudo apt-get update
sudo apt-get install samba

The install will require around 20 MB of space and take a few minutes.

Once the install has completed, we can make a copy of the configuration file as follows to allow us to restore to defaults if needed:

sudo cp /etc/samba/smb.conf /etc/samba/smb.conf.backup
sudo nano /etc/samba/smb.conf

Scroll down and find the section named Authentication; change the # security = user line to security = user.

As described in the file, this setting ensures that you have to enter your username and password for the Raspberry Pi in order to access the files (this is important for shared networks).

Find the section called Share Definitions and [homes], and change the read only = yes line to read only = no.

This will allow us to view and also write files to the shared home folder. Once done, save and exit by pressing Ctrl + X, Y, and Enter.

Now, we can add pi (the default user) to use samba:

sudo pdbedit -a -u pi

Now, enter a password (you can use the same password as your login or select a different one, but avoid using the default Raspberry password, which would be very easy for someone to guess). Restart samba to use the new configuration file, as follows:

sudo /etc/init.d/samba restart
[ ok ] Stopping Samba daemons: nmbd smbd.
[ ok ] Starting Samba daemons: nmbd smbd.

In order to test, you will need to know either the Raspberry Pi's hostname (the default hostname is raspberrypi) or its IP address. You can find both of these with the following command:

hostname

For the IP address, add -I:

hostname –I

On another computer on the network, enter the \\raspberrypi\pi address in the explorer path.

Depending on your network, the computer should locate the Raspberry Pi on the network and prompt for a username and password. If it can't find the share using the hostname, you can use the IP address directly, where 192.168.1.69 should be changed to match the IP address \\192.168.1.69\pi.

You will need to be connected to the Internet in order to update your system. It is always advisable to make a backup of your image first (and at a minimum, take a copy of your important files).

You can check your current version of firmware with the uname -a command, as follows:

Linux raspberrypi 4.4.9-v7+ #884 SMP Fri May 6 17:28:59 BST 2016 armv7l GNU/Linux

The GPU firmware can be checked using the /opt/vc/bin/vcgencmd version command, as follows:

   May  6 2016 13:53:23
Copyright (c) 2012 Broadcom
version 0cc642d53eab041e67c8c373d989fef5847448f8 (clean) (release) 
This is important if you are using an older version of firmware (pre-November 2012) on a newer board since the original Model B board was only 254 MB RAM. Upgrading allows the firmware to make use of the extra memory if available.

The free -h command will detail the RAM available to the main processor (the total RAM is split between the GPU and ARM cores) and will give the following output:

             total       used       free     shared    buffers     cached
Mem:          925M       224M       701M       7.1M        14M       123M
-/+ buffers/cache:        86M       839M
Swap:          99M         0B        99M

You can then recheck the preceding output following a reboot to confirm that they have been updated (although they may have already been the latest).

Before running any upgrades or installing any packages, it is worth ensuring you have the latest list of packages in the repository. The update command gets the latest list of available software and versions:

sudo apt-get update

If you just want to obtain an upgrade of your current packages, upgrade will bring them all up to date:

sudo apt-get upgrade

To ensure that you are running the latest release of Raspbian, you can run dist-upgrade (be warned; this can take an hour or so depending on the amount that needs to be upgraded). This will perform all the updates that upgrade will perform but will also remove redundant packages and clean up:

sudo apt-get dist-upgrade

Both methods will upgrade the software, including the firmware used at boot and startup (bootcode.bin and start.elf).

You will often find that you will want to perform a clean installation of your setup; however, this will mean you will have to install everything from scratch. To avoid this, I developed the Pi-Kitchen project (https://github.com/PiHw/Pi-Kitchen), based on the groundwork of Kevin Hill. This aims to provide a flexible platform for creating customized setups that can be automatically deployed to an SD card.

Pi Kitchen allows the Raspberry Pi be configured before powering up

The Pi-Kitchen allows a range of flavors to be configured, which can be selected from the NOOBS menu. Each flavor consists of a list of recipes, each providing a specific function or feature to the final operating system. Recipes can range from setting up custom drivers for Wi-Fi devices, to mapping shared drives on your network, to providing a fully functional web server out of the box, all combining to make your required setup.

This project is in beta, developed as a proof of concept, but once you have everything configured, it can be incredibly useful to deploy fully working setups directly onto an SD card. Ultimately, the project could be combined with Kevin Hill's advanced version of NOOBS, called PINN (short for PINN Is Not NOOBS), which aims to allow extra features for advanced users, such as allowing operating systems and configurations to be stored on your network or on an external USB memory stick.