I have replaced the two transistors that going from slave to master by simple diodes and finally work.
I thinked I was problems with ST levels on RC1 (as MISO) and I replaced this by TTL using another pin but it not was the problem and either other causes that I thinked and tested...
I need to pause this project sometimes (no much time) because I have multiples ownmade parts and these parts have brought me many headaches and many coding time and I need stop and take this long-term project with many calm, no hurries refactorings to easily understand any part after a long time and allow me touch new interesting projects too :)
I will need to make new clean PCBs soon. These are already somewhat touched and exist new small changes too
I'm going to test first learnings making the typical pendulum test. But I have only 1 slave now (1 sensor=MPU & 1 actuator=servo). I need other slaves to offer more sensors (without actuators for this configuration).
I wan't overload slaves making many things and anyway I will need to add other slaves with different sensors (ADC, etc...).