This is a simple Arduino script which would trigger a camera to take picture, if GPIO 12 and the power GND pin were wired to the two solder pads on a camera's circuit board.

Important: This code should be used with a resistor to prevent sending too high a voltage to the camera.

int camGPIO = 12;

void setup()
{
  pinMode(camGPIO, OUTPUT);
}

void loop()
{
  digitalWrite(camGPIO, HIGH);
  delay(500);
  digitalWrite(camGPIO, LOW);
  delay(5000);
}