The minimum is 1 millisecond, but you should never set it that short since it will frequently fire as the thread scheduler works at 1 millisecond timeslices, and any delays caused by high priority threads or disabled interrupts will exceed that limit.
The maximium varies by platform:
- Boron, B Series SoM, Argon, Tracker SoM (nRF52840): 131,071,999 milliseconds
- P2 and Photon 2 (RTL872x): 8,190,000 milliseconds (around 2 hours and 15 minutes)
You can only call
init() if the watchdog is not currently running. On the nRF52 platform (Boron, B Series SoM, Argon, Tracker SoM) you cannot stop the watchdog, so you necessarily can only start it once until the device is reset. This also means you cannot change the watchdog time period on the nRF52 platform.