I have a Raspi 3B rev: a02082 (Q1 2016 3 Model B 1.2 1 GB (Mfg by Sony)) running raspbian jessie kernel 4.9.35-v7
I want to signal to a power management circuit that filesystems have been un-mounted and now we can remove the power from the raspberry pi.
option when set in /boot/cmdline.txt is supposed to drive GPIO26 low after shutdown.
However, watching the pin on a scope, it stays at 0 volt irrespective of the state of the Pi (booted/shutdown)
I have tried changing the pin numbers in the
dtoverlay=gpio-poweroff parameters, also I have tried with and without the active_low option.
The GPIO pin is functional - because if I test with:
echo "26" > /sys/class/gpio/export
echo "out" > /sys/class/gpio/gpio26/direction
echo "1" > /sys/class/gpio/gpio26/value
I can see the pin go high on the oscilloscope.
- 1: Why might it not be working?
- 2: How can we debug the overlay?
- 3: Should we expect a spike/edge on the pin by the overlay on shutdown - or a continuous low/high?