Software Environment

The Raspberry Pi module runs a Debian-based operating system (32-bit Raspberry Pi OS) with a graphical user interface. For the experiments mainly these programs will be used:

• “Terminal” command line interface

• “Visual Code” integrated development environment for C and Python

• “Chromium” web browser to browse this documentation and other information

There are other editors / development environments available in the Raspberry Pi OS distribution which could also be used instead of “Visual Code” (for example “Geany”, “Thonny” etc.).

Folder Structure

The code examples and additional documentation is maintained on GitHub. The project structure on the Raspberry Pi file system is organized like this:

|__home
|  |__ Embedded-System-Lab (GitHub root directory)
|  |  |__ code (code examples in sub-folders for each experiment)
|  |  |__ docs (sources for this documentation)
|  |  |__ hardware (documentation: schematics, datasheets)
|  |__ work (user working directory, not synchronized to GitHub)

Note

User programs and measurement data should be saved in the work folder. The code examples found in the Embedded-System-Lab/code folder should not be modified but rather copied to the work folder and modified there, as needed. In case the content of the code or any other git folder were accidentally changed, the files can be restored by calling git checkout --force origin/master from the command line within the respective folder.

It is recommended that the user has some basic knowledge of Python (and a bit of C) language since this script does not provide an introduction to the programming languages. Online training with interactive tutorials can be found for example here:

• Python: https://www.w3schools.com/python/default.asp

• C: https://www.w3schools.com/c/index.php

Using Visual Code

Start Visual Code and open the folder Embedded-System-Lab/code via the menu File->Open Folder. In the explorer view one can find sub-folders for each experiment and additional helper functions. Most examples are written in Python while a few examples and low level functions (GPIO hardware register access and DMA for fast ADC operation) are implemented in C/C++. The Visual Code editor will allow comfortable code editing and integrates tool chains to run Python and C/C++ code. When you switch between Python and C sources you have to select the appropriate start and debug configuration for the given language: Click on the bottom status bar and select

• “C (Linux): Current file” for compiling and running C code

• “Python: Current File” for running Python scripts

Here are simple code examples to test the installation and explain the basic methods of the Visual Code IDE.

Python Example

Open the Visual Code Explorer panel and browse the code sub folder. Select the file Python script hello_world.py and copy it to your work folder and open it in the editor window. To run the script, click the menu Run->Run without Debugging, or press Ctrl+F5 or click the “play” button on the upper right corner of the editor window. This will invoke the Python interpreter and run the script. The output will be displayed in the Terminal panel at the bottom of the window. If the Terminal panel is not visible, open it via the menu View->Terminal.

C Example

Similar to the previous example, now select the C-file hello_world.c from the code folder, copy it to your work folder and open it in the editor window. Before you can execute the code you need to compile the file. Press Ctrl + Shift + B or go to Terminal->Run Build Task to start the build process. After that you can run the code with Run->Run without Debugging or by pressing Ctrl + F5. The output will be displayed in the Terminal panel at the bottom of the window. Of course one can also start the executable from a command line in a terminal.

A powerful tool to test your code and to solve issues is a debugger. By running your code in debug mode (pressing F5 instead of Ctrl+F5) you can define breakpoints by clicking on the column on the left-hand side of the line numbers. A red dot will appear which will halt the code execution at this point to allow the inspection of variables. From a breakpoint you can resume the code execution with F5 or execute step-wise by pressing F10 (or F11 which will step further down into the definition of called functions). See Visual Code documentation on the web for more details.

Note

A few examples like the C-exampleC-code for low-level GPIO access (see GPIO Programming Tutorial) and the library for the fast ADC, need access to protected physical memory resources from within the user space. This access requires privileged permissions (i.e. root access) to execute the code. To run these programs one has to call sudo -E ./<program name> from a command line because starting from within the Visual Code IDE would not provides root access.