How to set up a command-based communication using I2C

[david_2018]

@domi1

When the nRF is idle, the SCL and SDA pin stay at high (as it should be); but when I connect the M0 board to it, the voltage sometimes drops to 0V unless the M0 board is pluged in / flashed with a software. The nRF is then unable to output a signal. Is this supposed to happen? I'm not sure what exactly the cause of this voltage drop is as it only happens sometimes, but not always.

This would be expected when the M0 is not plugged in (unpowered). There are diodes on the input pins of almost all processors that prevent the pin from going more than about 0.7v above VCC, which in this case would be 0V since it is unpowered.