DFRobot FireBeetle ESP32-E Manual page 38

#define uS_TO_S_FACTOR 1000000ULL
#define TIME_TO_SLEEP 5
RTC_DATA_ATTR int bootCount = 0;
/*
Method to print the reason by which ESP32
has been awaken from sleep
*/
void print_wakeup_reason(){
esp_sleep_wakeup_cause_t wakeup_reason;
wakeup_reason = esp_sleep_get_wakeup_cause();
switch(wakeup_reason)
{
case ESP_SLEEP_WAKEUP_EXT0 : Serial.println("Wakeup caused by external signal using RTC_IO"); break;
case ESP_SLEEP_WAKEUP_EXT1 : Serial.println("Wakeup caused by external signal using RTC_CNTL"); break;
case ESP_SLEEP_WAKEUP_TIMER : Serial.println("Wakeup caused by timer"); break;
case ESP_SLEEP_WAKEUP_TOUCHPAD : Serial.println("Wakeup caused by touchpad"); break;
case ESP_SLEEP_WAKEUP_ULP : Serial.println("Wakeup caused by ULP program"); break;
default : Serial.printf("Wakeup was not caused by deep sleep: %d\n",wakeup_reason); break;
}
}
void setup(){
Serial.begin(115200);
delay(1000); //Take some time to open up the Serial Monitor
//Increment boot number and print it every reboot
++bootCount;
Serial println("Boot number: " + String(bootCount));
/* Conversion factor for micro seconds to seconds */
/* Time ESP32 will go to sleep (in seconds) */