.. currentmodule:: machine
.. _machine.WDT:

class WDT -- watchdog timer
===========================

The WDT is used to restart the system when the application crashes and ends
up into a non recoverable state. Once started it cannot be stopped or
reconfigured in any way. After enabling, the application must "feed" the
watchdog periodically to prevent it from expiring and resetting the system.

Example usage::

    from machine import WDT
    wdt = WDT(timeout=2000)  # enable it with a timeout of 2s
    wdt.feed()

Availability of this class: pyboard, WiPy, esp8266, esp32.

Constructors
------------

.. class:: WDT(id=0, timeout=5000)

   Create a WDT object and start it. The timeout must be given in milliseconds.
   Once it is running the timeout cannot be changed and the WDT cannot be stopped either.

   Notes: On the esp32 the minimum timeout is 1 second. On the esp8266 a timeout
   cannot be specified, it is determined by the underlying system.

Methods
-------

.. method:: WDT.feed()

   Feed the WDT to prevent it from resetting the system. The application
   should place this call in a sensible place ensuring that the WDT is
   only fed after verifying that everything is functioning correctly.
