Programming ARM microcontroller is really an interesting activity.
However, as there are many different build tools, librairies, SoC types and boards, starting a new project from scratch can be frustrating.
Here you will find some projects for different boards that use:
- the GNU Embedded Toolchain for ARM;
- libopencm3;
- and FreeRTOS.
The GNU Embedded Toolchain for ARM can be downloaded here: https://developer.arm.com/open-source/gnu-toolchain/gnu-rm/downloads
The libopencm3 can be downloaded here: https://github.com/libopencm3/libopencm3
The FreeRTOS can be downloaded here: https://www.freertos.org/
I hope it can help !