Hi @felmue,

I started M5Core2-Factory test, disconnected USB and go away. About 5 hours later I came back and tried to switch on M5Core. Nothing happened.

I connected USB, flashed the M5Core2 with the factory test program and everything worked fine.

At the last day I used my RTC-library with alarm functions and more and it worked continuously.

Cheers

In another thread, it became clear that the most appropriate fix for this issue in the factory test code is:
On lines 446 and 447, in the function checkI2cAddr():
Change one instance of Wire. to Wire1. one each of the two lines.

Wire.beginTransmission( lastptr->addr ); if ( Wire.endTransmission() == 0 )

...becomes:

Wire1.beginTransmission( lastptr->addr ); if ( Wire1.endTransmission() == 0 )