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.

  • 2
    Never connect a Pi GPIO to more than 3V3.
    – joan
    Commented Nov 6, 2017 at 22:20


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