This code drives a simple circuit that engages the shutter in single-frame mode on my super 8 camera.
It uses a heart rate monitor (Pulse Sensor Amped) as analog input to an Adafruit ItsyBitsy. The signal from the monitor sets the voltage at pin A1, which is read and when it's within a certain value range, pin D7 is triggered to close the shutter circuit.
Pin D5 acts as an indicator so I can see when the monitor's signal has settled into an accurate reading of my pulse, before I engage the camera.
We'll see what comes of it!