Adafruit SleepyDog Arduino Library 
Arduino library to use the watchdog timer for system reset and low power sleep.
Currently supports the following hardware:
- Arduino Uno or other ATmega328P-based boards.
- Arduino Mega or other ATmega2560- or 1280-based boards.
- Arduino Zero, Adafruit Feather M0 (ATSAMD21).
- Adafruit Feather M4 (ATSAMD51).
- Arduino Leonardo or other 32u4-based boards (e.g. Adafruit Feather) WITH CAVEAT: USB Serial connection is clobbered on sleep; if sketch does not require Serial comms, this is not a concern. The example sketches all print to Serial and appear frozen, but the logic does otherwise continue to run. You can restore the USB serial connection after waking up using
USBDevice.attach();and then reconnect to USB serial from the host machine. - Partial support for Teensy 3.X and LC (watchdog, no sleep).
- ATtiny 24/44/84 and 25/45/85
- ESP32, ESP32-S2, ESP32-S3
- ESP8266 WITH CAVEAT: The software and hardware watchdog timers are fixed to specific
intervals and not programmable. Notes about this are within the
utility/WatchdogESP8266.cppfile.