I've fixed a hardware watchdog (switchdoc labs dual watchdog timer) to my Pi (3b+) and are having some issues. The watchdog is used to power a relay to power cycle the pi. I have a program that sends a heart beat to pat the watchdog from pin37. Once the program is up and running the watchdog works fine and will trigger a reset if the heart beat doesn't appear for the allotted timeout period. However, if the program hasn't been run then the watchdog timer appears to be stuck. When the pi boots the voltage between pin37 and GND is 1.65V. The watchdog specifies that the trigger pin (pin37) should be held high impedance and then pulled to ground to pat the dog. In order to unstick the watchdog, the line...
... is called and this sets the timer counting again. After this point, the voltage will move between 4.9V (I assume this is high impedance) and GND (when pulled to ground by pin37). The watchdog needs to be able to reset the pi if the program fails to run and at the moment, this isn't happening unless the program is run in the first place.
Any thoughts greatly appreciated, thanks