Update libopencm3 framework

[qosch]

I am having issues building a simple program using the libopencm3 framework and someone on the forum concluded this is due to an old version of libopencm3 (Thread: https://community.platformio.org/t/compiler-doesnt-find-function-definition-libopencm3/25795). Could this be updated? Thanks :)

[larmicfre]

It's actually possible to use custom packages in your enviroment, defined in your platformio.ini. I've forked libopencm3 library and added the required packages.json file. I'll fetch upstream upon new commits.

To use the latest libopencm3 library in your project, open platformio.ini and paste the following line. platform_packages = framework-libopencm3 @ https://github.com/larmicfre/libopencm3.git

Don't forget to clean your enviroment.