ESP32 with PlatformIO, C++, Unity and ESPIDF

As a follow up to my post about ESP32 with PlatformIO and Arduino, in this post I present how to use PlatformIO with the Espressif IDF (or ESPIDF, for short) in conjunction with C++ and Unity as a UnitTesting framework.

It proved to be much more difficult to get this running than with the Arduino framework.

Here are our requirements for development:

1. Support (hardware and framework independent) unit tests to be run on the local dev machine (aka env:native).
2. Support hardware and framework specific unit tests to be run on the actual microcontroller.

Here are some similarities and differences between ESPIDF and Arduino:

• Again, the native environment will be compiled via SYS2/Mingw64 whereas the microcontroller environments are compiled by the compilers provided by the PlatformIO toolchain.
• ESPIDF uses app_main() instead of the setup()/loop() construct in Arduino.
• ESPIDF by default creates a main.c instead of a main.cpp file. We therefore have to use extern "C" { } to unmangle the symbols in our code.
• For whatever reason the use of #ifdef __cpluscplus always evaluated to false and was therefore not usable. Thus, I used extern "C" unconditionally in the code.
• To detect the ESPIDF framework, I used the ESP_PLATFORM symbol (instead of the ARDUINO symbol).
• All framework dependent cpp and h lib files are guarded with #if defined(ESP_PLATFORM).
• All test code (test_embedded and test_native) has to be surrounded with extern "C" as well (only the code and certinaly not the #includes).
• Classes and code in lib_dir should not be surrounded with extern "C".
• Also, I pretty much moved all the code to lib_dir, so the main.cpp is essentially only a stub.
• We have to manually enable exceptions to support throw etc via build_flags: -fexceptions.
• (not unit test related) Reading out GPIO to get the state of an LED always returns 0.

The final result can be found here.

Summary

Again, it is quite quirky to setup the development environment. Plus, I could not find a single example out in the wild (PlatformIO in conjunction with C++, Unity with embedded and native testing, ESPIDF).

In the end, I now have a working environment where I can hopefully do what I want to do: sending and receiving CAN messages via the TWAI interface. We will find out …