Ex-00: Getting Started with STM32, VS Code and Saleae¶

The editor used for writing the code and programming the microcontroller will be Visual Studio Code. This is well suited to the students’ experience as it is the text editor used in other programming classes. Visual Studio Code is not specifically designed to work with C/C++ or with a microcontroller. It is more like a general purpose text editor with syntax highlighting and a plug-in interface for all sorts of extensions. However, the extensions make it easy to install a toolchain for your target architecture. The aim of this lab exercise is to install and configure all the necessary components so that you can build, run and debug a first flashing LED on the microcontroller.

Description¶

The Visual Studio code editor will be used throughout this course to program the microcontroller. Although a complete development environment is available from the microcontroller vendor (STM32CubeIDE), it obscures many of the topics covered in this course. For the vast majority of toolchains, regardless of the target platform, it is possible to use them in an environment of your choice. The simplest example is to use a text editor to edit your files and run the toolchain from the console. You may have already gained some experience of doing this in the introductory course to the C programming language in the first semester of study. As the complexity and size of a toolchain increases, it is recommended that you use a development environment to help you manage the necessary components of your toolchain. This environment is referred to as an Integrated Development Environment (IDE). There are many IDE’s available from hardware and software vendors. However, this means that you have to use different IDEs for different projects. To counter this trend, many modern IDEs consist of just a text editor and a package manager for extensions. The individual toolchains for different target platforms can also be installed as packages. In this way, it is possible to serve different languages and different target platforms from a single IDE. For this course and the other basic programming courses, Visual Studio Code is used as the IDE. This is because this IDE is widely used in the industry and is also available on most platforms.

Installation and Initial Setup¶

For this course, as always, we provide a pre-installed virtual machine with the latest LTS version of Ubuntu GNU/Linux. If you do not already have it installed, follow the instructions in the README file linked on the e-learning plattform to boot your copy of the virtual machine.

It is not an OEM standard installation, as we have pre-installed some of the most important programs and tools you will use. The editor visual studio code is pre-installed. However, the necessary extensions and packages for creating a microcontroller project are still missing.

Template at a Glance¶

To save time when setting up a microcontroller project, a template has been created. You can clone or download the MCU template from gitlab. This template provides all necessary files to compile, debug and flash the project for a STM32-F446re controller.

A brief explanation of the most important files and directories:

• .vscode

  In this directory are some settings for VSCode, which are used for building and debugging the project in VSCode.

• Drives/CMSIS

  The CMSIS directory contains important information about the STM32-F446re MCU and will be explained in more detail later on.

• src

  This directory contains the basic main.c file and allows you to add your additional source and header files.

• Makefile

  The Makefile contains basic rules and recipes to compile a C project. It optimises the compilation process and reduces the user effort involved in building.

• STM32F446.svd

  The CMSIS System View Description format (CMSIS-SVD) formalizes the description of the system contained in Arm Cortex-M processor-based microcontrollers, in particular, the memory mapped registers of peripherals. (Extracted from Arm Keil web page about System View Description)

• STM32F446RETx_FLASH.ld

  This is the linking script used by the linker as part of the compilation process to correctly link the libraries used and generate a single machine code executable.

• openocd.cfg

  This config file is used by the debugger to locate and communicate with the ST-LINK on the NULCEO-64 board.

• stm32_startup.c

  This is used to implement the startup process to set up the hardware state correctly. It ends by calling the main() function.

Ubuntu Packages¶

The virtual machine does not have the base packages for an MCU project installed.

Start VS Code¶

Move into the directory where your cloned or downloaded template is located in the terminal. Open VSCode with with the command:

code .

The command code opens VSCode, the argument . references a folder or a file, in this case the current directory. When VSCode is started for the first time, a welcome message is displayed.

You can choose your own settings for the display, but this will not be part of this exercise since the defaults work fine.

VS Code Extensions¶

Add the extensions for vs-code listed in README below the ubuntu packages. The extensions are briefly explained:

• Cortex-Debug

  ARM Cortex-M GDB Debugger support for VSCode

• C/C++ Extension Pack

  Popular extensions for C/C++ development in Visual Studio Code, includes syntax highlighting, autocompletion and error and warning descriptions

VS Code at a Glance¶

On the left is a menu bar that gives you access to the most common functions:

• Explorer

  Keep track of all the files and directories in the folder that is currently open

• Search

  Search bar to find files, directories, functions or words in files

• Source control

  Git source control with a user interface. Of course, you can still use the Terminal

• Run and Debug

  You can run and debug your program by observing the current states of variables and registers for as long as the debugger is paused.

• Extensions

  View installed extensions, search for new extensions and get recommendations for new useful extensions.

Explanation side panels

Compile and Flash¶

With the help of the Makefile, these processes are automated. There are several possibilities to run these jobs.

Compile¶

Flash¶

USB Settings¶

By default, your virtual machine does not have access to the hardware interfaces and devices of your host computer. Therefore, you need to add this permission. You can do this manually for each session or set it once for your virtual machine. To enable a permanent USB connection to your virtual machine, read the USB Settings article in the FAQ section.

In the future, if you want to make other USB devices persistent in your virtual machine, you will need to follow the same procedure.

Run Flash Command¶

Open a terminal described in the Compile section and use the command:

make flash

Debug¶

Debug Configuration¶

The final step is to learn how to debug your program in Visual Studio Code. By installing the toolchain and extensions and using the template, all the tools are already available and you should be able to examine the ARM specified “Cortex Registers” at runtime. The configuration file to link these registers with the correct address is the “STM32F446.svd” and is called in the launch file in .vscode/launch.json.

Start Debugger¶

To start the debugger, no other debug process must be running on the STM32 board. There are several ways to start the debugger.

Debugger Menu¶

This is a brief overview of the sections and panels available in Debugger mode:

Debugger Menus

Debug Actions¶

To control the debugging, Visual Studio Code provides a user-friendly control panel. Read the part about the VS-Code Debug Action Buttons.

As a first step, pause the programme and have a look at the current state of the programme:

• On which line are you in the programme?

• Can you see the current register value of RCC, which belongs to the register named CR (clock control register)?

Saleae Logic Analyzer¶

Next, we start with a brief introduction to the saleae logic analyzer. This device allows you to read digital inputs, analogue inputs and interpret communication protocols. The aim is to download and install the official saleae application, connect the logic analyzer to your computer and read a digital and analogue value.

Download and Install¶

First, download the logic 2 application from Saleae Download and installation. Read the Installation Instructions for your operating system. For GNU/Linux users, see the FAQ in the official website section.

Exercise¶

Objective¶

The aim is to get a first experience with the saleae, including reading an analogue and digital value and making a first measurement. The analogue value is the left potentiometer, called POT_I in the schematic. The digital signal is the switch center.

Basic information¶

The first step is to watch the videos linked below:

• capturing data to learn the absolute basics

• organize workspace for tips and tricks to use the application more effectively

Connect to the Nucleo-64 board¶

Refer to the schematic of the Thermocouple Expansion Board schematic or the PCB Description for the correct pins for the hardware used and connect PIN 0 of saleae to the SW_CENTER pin on the Morpho connector. Connect POT_I to PIN 1 of the saleae.

At the end, connect a ground wire (saleae G) to the ground of the Nucleo-64 board.

Measure the inputs¶

Start the application and take a first measurement as learned in the capturing data. Read different values and observe the behaviour in the application by pressing the middle button and turning the potentiometer. Answer following questions: