Deep Sleep Elapsed Time

/*
  Developed by William Lucid with assist from OpenAI's, ChatGPT
  04/26/2023
*/

#include "esp_sleep.h"

int switchPin = 27;  // Use GPIO27 for the switch pin
int switchState = HIGH;  // Current state of the switch
int lastSwitchState = HIGH;  // Last state of the switch
unsigned long lastDebounceTime = 0;  // Time since last switch debounce
unsigned long debounceDelay = 50;  // Delay for switch debouncing
bool switchDetected = false;  // Flag for switch detection

RTC_DATA_ATTR unsigned long currentSleepTime = 0;
RTC_DATA_ATTR unsigned long lastSleepTime = 0;
RTC_DATA_ATTR unsigned long elapsed = 0;

void IRAM_ATTR gotSwitch() {
  switchDetected = true;
}

void setup() {

  Serial.begin(9600);

  while(! Serial){}

  Serial.println("Ready");

  // Configure external wakeup source
  pinMode(switchPin, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(switchPin), gotSwitch, FALLING);

  // Configure sleep mode
  esp_sleep_pd_config(ESP_PD_DOMAIN_RTC_PERIPH, ESP_PD_OPTION_ON);
  esp_sleep_pd_config(ESP_PD_DOMAIN_RTC_SLOW_MEM, ESP_PD_OPTION_ON);
  esp_sleep_enable_ext1_wakeup(1ULL << switchPin, ESP_EXT1_WAKEUP_ANY_HIGH);

}

void loop() {

  // Read the current state of the switch and debounce it
  int reading = digitalRead(switchPin);
  if (reading != lastSwitchState) {
    lastDebounceTime = millis();
  }
  if ((millis() - lastDebounceTime) > debounceDelay) {
    if (reading != switchState) {
      switchState = reading;
      if (switchState == LOW) {
        switchDetected = true;
      }
    }
  }
  lastSwitchState = reading;

  // If the switch has been detected, print the elapsed sleep time
  if (switchDetected) {
    switchDetected = false;
    Serial.println("Wakeup enabled");
    currentSleepTime = micros();
    float elapsed = (currentSleepTime - lastSleepTime) / 1000000.0;
    Serial.println("Sleep time:  " + String(elapsed) + "  Seconds");
    lastSleepTime = currentSleepTime;
    Serial.println("Going to Deep Sleep...");
    esp_deep_sleep_start();
  }

}