ESP32 Watchdog

from https://github.com/espressif/arduino-esp32/blob/master/libraries/ESP32/examples/Timer/WatchdogTimer/WatchdogTimer.ino

	#include "esp_system.h"
	const int button = 0; //gpio to use to trigger delay
	const int wdtTimeout = 3000; //time in ms to trigger the watchdog
	hw_timer_t *timer = NULL;
	void IRAM_ATTR resetModule() {
	ets_printf("reboot\n");
	esp_restart();
	}
	void setup() {
	Serial.begin(115200);
	Serial.println();
	Serial.println("running setup");
	pinMode(button, INPUT_PULLUP); //init control pin
	timer = timerBegin(0, 80, true); //timer 0, div 80
	timerAttachInterrupt(timer, &resetModule, true); //attach callback
	timerAlarmWrite(timer, wdtTimeout * 1000, false); //set time in us
	timerAlarmEnable(timer); //enable interrupt
	}
	void loop() {
	Serial.println("running main loop");
	timerWrite(timer, 0); //reset timer (feed watchdog)
	long loopTime = millis();
	//while button is pressed, delay up to 3 seconds to trigger the timer
	while (!digitalRead(button)) {
	Serial.println("button pressed");
	delay(500);
	}
	delay(1000); //simulate work
	loopTime = millis() - loopTime;
	Serial.print("loop time is = ");
	Serial.println(loopTime); //should be under 3000
	}

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