All the code examples for this chapter can be found on GitHub at https://github.com/PacktPublishing/Bare-Metal-Embedded-C-Programming.

There are several ways to develop the firmware for a particular microcontroller depending on the resources provided by the microcontroller’s manufacturer. When it comes to developing firmware for STM32 microcontrollers from STMicroelectronics, we can use the following:

• Hardware Abstraction Layer (HAL): This is a library provided by STMicroelectronics. It simplifies the process by offering high-level APIs for configuring every aspect of the microcontroller. What is great about HAL is its portability. We can write code for one STM32 microcontroller, and easily adapt it for another, thanks to the uniformity of their APIs.
• Low Layer (LL): Also from STMicroelectronics, the LL library is a leaner alternative to HAL, offering a faster, more expert-oriented approach that’s closer to the hardware.
• Bare-Metal C programming: With this approach, we dive right into the hardware, accessing the microcontroller’s registers...

In this section, our focus is to pinpoint the specific ports and pins on the microcontroller to which the user LED, user push button, berg pins, and Arduino-compatible headers are connected on the development board. Understanding these connections is crucial for our programming tasks. To accurately identify these connections, we will consult the NUCLEO-F411 User Manual.

Figure 2.2: Development board showing components of interest

Now, let’s locate the microcontroller pin connected to the User LED on the development board.

Locating the LED connection

Our first step is to navigate through the table of contents to find the section dedicated to LEDs. This can be done quickly by locating Figure 2.3 in the manual, which shows the page number for the LEDs section and allows us to jump directly to it.

Click on the page number to jump to the LEDs section.

...

In the previous section, we established that the User LED is connected to pin PA5. This means that it is linked to pin number 5 on GPIO PORTA. In other words, to get to the LED, we have to go through PORTA and then locate pin number 5 of that port.

As illustrated in Figure 2.10, the microcontroller has exposed pins on all four sides. These pins are organized into distinct groups known as ports. For instance, pins in PORTA are denoted with the PA prefix, while those in PORTB start with PB, and so forth. This systematic arrangement allows us to easily identify and access specific pins for programming and hardware interfacing tasks.

Figure 2.10: STM32F411 pinout

In the next section, we will go through the steps to locate the precise address of GPIO PORTA.

Locating GPIO PORTA

To effectively interact with any part of our microcontroller, it’s essential to know the memory address...

In this section, we will apply the knowledge acquired throughout this chapter to develop our first bare-metal firmware.

We begin by creating a new project, a process we covered in Chapter 1. Here is a summary of the steps:

1. Start a new project: Go to File | New | STM32 Project in your IDE.
2. Select the target microcontroller: A Target Selection window will appear, prompting you to choose the microcontroller or development board for your project.
3. Use the board selector: Click on the Board Selector tab.
4. Search for our board: Input NUCLEO-F411 in the Commercial Part Number field.
5. Select our board: From the list of boards that appear, choose NUCLEO-F411RE and then click Next.
6. Name our project: Assign a name to your project, for instance, RegisterManipulation.
7. Project configuration: In the project options, select an Empty project setup.
8. Final step: Click Finish to create...

In this chapter, we delved into the core of bare-metal programming, emphasizing the direct interaction with microcontroller registers. This gave us insight into some of the key registers of our microcontroller and the structure of those registers.

We began by exploring various firmware development approaches, each offering a distinct level of abstraction. These approaches included the HAL, LL, Bare-Metal C programming, and the assembly language. This exploration helped us understand the trade-offs and applications of each approach in firmware development.

We spent a significant part of the chapter defining addresses of some peripherals using the official documentation. This step was important in creating addresses for various registers within those peripherals. It involved gathering specific memory addresses, typecasting them for register access, and creating aliases for bits in the registers.

The chapter culminated in a practical application where we configured PA5...