I have a very simple circuit using the Adafruit breakout Pi cobbler kit with a HC-SR04 ultrasound module. The circuit works fine (I can trigger and read the echo back) but it doesn't seem to be correctly grounded. It only works when I put my hand near the Pi breakout ribbon cable (and my code waits for a rising edge until I complete the circuit :)
The Pi itself has only micro-usb power connected to the mains and an ethernet connection. For info, the GPIO connections are:
- Pin 2 (5v) -> Vcc pin of module
- Pin 6 (ground) -> Ground pin of module
- Pin 7 -> echo
- Pin 11 -> trigger
What should I be doing to ground this correctly?