The watchdog period is set to ~20ms, twice the period of the main
loop. This updates the fan PWM values at every 10ms cycle; every 100
cycles (1 second) it also reads the fan sensor counters and triggers
the ADC to start a new measurement cycle.

Maybe worth noting, the watchdog cannot be used to check I2C comms:
this is the master's job, it can decide to power cycle the monitoring
module remotely if it's not responsive.