I was building Circuitpython from the github repro from adafruit. This was working for a raspi pico well. I could compile and dounload the firmware.uf2 -> Thonny everthing look OK. Next I wanted to add a C-written module. Doing as described by adafruit was OK until the point:

ports/atmel-samd

We'll need to edit two files to hook our new module into the build: Makefile

We need to add the c files we added to shared-module to the SRC_SHARED_MODULE list:

mymodule/init.c
mymodule/MyClass.c \

I do not know where to find the SRC_SHARED_MODULE list and where to make the changes?

Thank you for the help.

Tips where to insert then module name