lowpower_example.ino

#include <WiFi.h>
#include <HTTPClient.h>

RTC_DATA_ATTR int bootCount = 0; // RTC_DATA_ATTR saves stuff in the RTC memory

const char* ssid = "*******";
const char* password = "********";

const int  uS_TO_S_FACTOR = 1000000;  /* Conversion factor for micro seconds to seconds */
const int S_TO_M_FACTOR = 60;
const int TIME_TO_SLEEP = 3;

const byte BTN1 = D19;
const uint64_t BTN1_mask = 1ULL << BTN1;

void print_wakeup_reason(){
  esp_sleep_wakeup_cause_t wakeup_reason;

  wakeup_reason = esp_sleep_get_wakeup_cause();

  switch(wakeup_reason)
  {
    case 1  : Serial.println("Wakeup caused by external signal using RTC_IO"); break;
    case 2  : Serial.println("Wakeup caused by external signal using RTC_CNTL"); break;
    case 3  : Serial.println("Wakeup caused by timer"); break;
    case 4  : Serial.println("Wakeup caused by touchpad"); break;
    case 5  : Serial.println("Wakeup caused by ULP program"); break;
    default : Serial.println("Wakeup was not caused by deep sleep"); break;
  }
}

void setup(){
  Serial.begin(115200);
  delay(1000); //Take some time to open up the Serial Monitor
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi..");
  }
 
  Serial.println("Connected to the WiFi network");
    
  //Increment boot number and print it every reboot
  ++bootCount;
  Serial.println("Boot number: " + String(bootCount));

    if ((WiFi.status() == WL_CONNECTED)) { //Check the current connection status
 
    HTTPClient http;
 
    http.begin("http://jsonplaceholder.typicode.com/comments?id=10"); //Specify the URL
    int httpCode = http.GET();                                        //Make the request
 
    if (httpCode > 0) { //Check for the returning code
 
        String payload = http.getString();
        Serial.println(httpCode);
        Serial.println(payload);
      }
 
    else {
      Serial.println("Error on HTTP request");
    }
 
    http.end(); //Free the resources
  }
 
  delay(10000);
  
  //Print the wakeup reason for ESP32
  print_wakeup_reason();

  esp_sleep_enable_timer_wakeup(TIME_TO_SLEEP * uS_TO_S_FACTOR * S_TO_M_FACTOR);

  esp_sleep_enable_ext1_wakeup(BTN1_mask, ESP_EXT1_WAKEUP_ALL_LOW);

  //Go to sleep now
  Serial.println("Going to sleep now");
  esp_deep_sleep_start();
}

void loop(){} // needed because of arduino