Hello there,
we use the PicoCoreMX8MM and we use one GPIO to be able to reset another MCU on the board.
Now we have realised that everytime the PicoCore reboots, the MCU also resets, which means the GPIO line triggers the reset.
This is our setup simplified:
So we have an external pull-up resistor pulling to line to 3V3.
According to the datasheet of the i.MX8MM all the GPIOs reset with an internal pull-down enabled.
In the device-tree picocoremx8mm.dtsi the pin is also configured to use the internal pull-down.
So I changed that value to 0x00140 (enable pull-up) in the device-tree files for the kernel and u-boot.
Still no change in behaviour, the MCU still resets whenever the PicoCore reboots.
So I took a look at the signal line at reset:
Here I see that after reset the pull-down is active and the line is at ~2,8V, after some time U-Boot configures the pin to use the pull-up and the line goes up to 3V3.
What I can't explain is the short drop to ~1,5V right at the beginning of the reset.
From a previous post here I know that the SW-Reset is done by resetting the PMIC, which then reset everything.
Could that somehow play a role in our issue?
Is it possible that all the pins are pulled low at reset due to the PMIC reset?
Or does this pin (GPIO_J2_77) have any special behaviour, because in the device-tree there is an option for it to be used for USB-C OTG alert?
Thank you guys in advance!
Best regards,
Stefan