Using the External Watchdog Timer
Operation
The MAX706RESA "microprocessor supervisor" expects a rising or falling transition on WDI
at least once every 1.6 seconds, otherwise it will pull the RESET
line LOW (given the circuit configuration above). On PyCubed, this would result in a power reset of the primary flight computer (SAMD).
Software/Firmware
In order to pulse the WDI
line at least once every 1.6s without incurring unnecessary processing overhead within CircuitPython, the pulse behavior is established at the C++ level when building CircuitPython for the PyCubed board.
- pulsing of
WDI
is enabled in firmware by default.
- see PyCubed's board.c definition in the CircuitPython source for more details.
⚠ CAUTION ⚠
Proper pulsing of WDI
is performed at all times once the board is powered except when the microcontroller is in bootloader mode. If you've already enabled the WDT (soldering R42) and need to enter the bootloader (unlikely), you'll need to first remove R42.