Here is the firmware of a cottonelle button, dumped using ST-Link v2:

https://drive.google.com/file/d/0B3Uf26cVOCONTjFONkgzZzVhWms/view?usp=sharing

Skipping through the firmware and sure enough there are some juicy bits inside:

As for the debug serial output under a number of situations, see here.