I am working with three Raspberry Pi 3 B boards, which in turns have RPi camera modules V2 connected to each. I followed this very detailed post about triggering another Pi using GPIO pins and it works exactly as stated. I am able to trigger the camera on the second Pi by setting output pin 18 to High.
My pins are connected as follows:
- Pin 25 of Pi 1 is connected to the switch (5V)
- Pin 18 or Pi 1 is connected to pin 23 of itself and pin 23 of Pi2.
- Two Pi's have their grounds connected.
Configured as such, I have the camera module on Pi 2 take pictures, not two together. If the second Pi pin 23 is disconnected, Pi 1 takes pictures.
I tried to see whether voltages on pins 23 are not sufficient, but they are so unstable, I cannot measure them properly with a voltmeter.