Hello,
I would like to use the Watchdog of the Xiao. Unfortunately I don´t find any examples.
How to use the internal Watchdog?
Cheers
Boris
SleepyDog does work for the XIAO SAMD21 Cortex M0+, but because I couldn’t find out what the macro is for distinguishing an XIAO SAMD21 Cortex M0+, I had to remove all the device selection code from the Adafruit_SleepyDog.h file. I also had to move the code from the .cpp file, into the .h file, to get it to work [because I don’t know how to get the Arduino IDE to compile .cpp files]:
/*!
* @file Adafruit_SleepyDog.h
*/
#ifndef ADAFRUIT_SLEEPYDOG_H
#define ADAFRUIT_SLEEPYDOG_H
// Platform-specific code goes below. Each #ifdef should check for the presence
// of their platform... yeah, right... if I could only find it! Until then, it's
// hard-coded for the XIAO!
#include "utility/WatchdogSAMD.h"
typedef WatchdogSAMD WatchdogType;
extern WatchdogType Watchdog;
// -----------------------------------------------------------
// Moved from the Adifruit_SleepDog.cpp file:
/*!
* @brief Global instance of the main class for sketches to use.
*/
WatchdogType Watchdog;
// -----------------------------------------------------------
#endif
WARNING: You can brick your XIAO [and probably any Arduino device]!! If you inadvertently put the device in a short timeout loop, it may become impossible to upload a new image because the USB driver gets interrupted, over and over, causing it to repeatedly disconnect! This happened to me, and I was only able to save the thing because the watchdog timeout was set to 1 second (it took several tries). And, yeah, I get that it wasn’t actually “bricked” - but it could have been 
The XIAO, in particular, is vulnerable to unstable code, in general, so when I’m developing, I add a 10 second delay to the Setup() function, as an “anti-brick” measure. 10 seconds is probably overkill, but haven’t found the time to titrate that to an optimal interval.