It sounds like the peripheral board is pulling the I2C lines high even if the Pi is off. That isn't allowed as it causes the ESD protection in the GPIO pin driver to conduct and some voltage leaks through onto the internal Pi power rails. The PMIC enforces strict power sequencing by only starting up once all outputs are at 0V.
Measure GPIO8/SDA when the Pi is off. If its not at 0V then you've got this problem.
Do you have the schematic for this peripheral board?
Measure GPIO8/SDA when the Pi is off. If its not at 0V then you've got this problem.
Do you have the schematic for this peripheral board?
Statistics: Posted by trejan — Sun May 05, 2024 11:38 pm