... fail due to C / C++ incompatibilities. An AI agent would be very good at turning an Arduino C++ library into pure C code you can include from the supplementary code window.

Further to @chipfryer27's suggestion, there is more info about the Supplementary Code feature in the wiki and there are many posts on the forum that discuss it too. For example, see here:
https://www.flowcode.co.uk/forums/viewtopic.php?t=3359

Hi

In Project Options, within the Other Options section you have a checkbox to Use Supplementary Code. If you tick tihis you can then specify a library to include.

Regards

External code can be included in Supplementary Code. See: https://www.flowcode.co.uk/wiki/index.php?title=Supplementary_Code Instead of adding the code directly to Flowcode, add statements into Supplementary Code such as the following to ...

... has a 'correction' formula - for the angle - the macro is still there - but using it gives a spiral effect - my maths isn't up to the job? Supplementary code holds the code to create a UART and receive data from the LiDAR (with a bigger buffer) - and to send commands. This data is then ...

Odd - the main directory should be created with the project - you could try either pasting the .h and .c files into the supplementary code (instead of the #includes) or give them a fixed address (#include "c:/test/file.h")

Martin

ok I create main and all...

Yes - supplementary.h & .c need to go into tiny_usb (project directory) /main/includes - and add includes to CMakeLists.txt as above.

Martin

I made a copy of supplementary.c supplementary.h from the supplementary folder to Tiny_usb
I did not help...

... the purchasing process and adopted the 2-tier standard/pro strategy we now have. There are other ways to incorporate C code into your Flowcharts - Supplementary Code and the Code flowchart icon. I realise these will not show the visual structure as you would like, but you might be able to use "Flowcode" ...