Low power WiFi Connection

lowpowerwifi.ino

#include <Arduino.h>

#if defined(ESP8266) 
  #include <ESP8266WiFi.h> 
#elif defined(ESP32) 
  #include <WiFi.h> 
#endif 
#include <WiFiClient.h>
#include <time.h>

// #include "secrets.h" 
#ifndef SECRETS_H 
 #define SECRETS_H 
const char WIFI_SSID[]              = "xxx"; 
const char WIFI_PASSWORD[]          = "xxxx";
#endif 

const uint64_t SLEEPTIME             = 10e6; // 10 seconds for test

const char TIME_NTPSERVER_1[]        = "nl.pool.ntp.org";
const char TIME_NTPSERVER_2[]        = "pool.ntp.org";

/*
 * Station connected 
 * @param WiFiEventStationModeConnected stationInfo struct of String ssid, uint8 bssid[6], uint8 channel
 */
void onSTAConnected(WiFiEventStationModeConnected stationInfo) { 
//  Serial.printf("%u: onSTAConnected\n", millis());
/*  Serial.printf("SSID: %s BSSID: %02x:%02x:%02x:%02x:%02x:%02x, Channel: %d\n", 
    stationInfo.ssid.c_str(),
    stationInfo.bssid[0], stationInfo.bssid[1], stationInfo.bssid[2], stationInfo.bssid[3], stationInfo.bssid[4], stationInfo.bssid[5],
    stationInfo.channel );
    */
} 

/*
 * Got IP 
 * @param WiFiEventStationModeGotIP ipInfo struct of IPAddress ip, IPAddress mask, IPAddress gw 
 */
void onSTAGotIP(WiFiEventStationModeGotIP ipInfo) {
/*  Serial.printf("IP: %s Mask: %s Gateway: %s\n", 
    ipInfo.ip.toString().c_str(),
    ipInfo.mask.toString().c_str(),
    ipInfo.gw.toString().c_str() ); 
   */ 
} 
  
/*
 * Station disconnected 
 * @param WiFiEventStationModeDisconnected disconnectedInfo struct of String ssid, uint8 bssid[6], WiFiDisconnectReason reason 
 * WiFiDisconnectReason, see https://github.com/esp8266/Arduino/blob/master/libraries/ESP8266WiFi/src/ESP8266WiFiType.h
 */
void onSTADisconnected(WiFiEventStationModeDisconnected disconnectInfo) { 
  // Serial.printf("Disconnected from SSID: %s\n", disconnectInfo.ssid.c_str()); 
  // Serial.printf("Reason: %d\n", disconnectInfo.reason); 
  // WiFi.reconnect();
} 

void connectToWiFi() { 
  //Serial.printf("%u: ConnectToWiFi start\n", millis());
  WiFi.forceSleepWake();
  delay(1);
  WiFi.persistent(false);
  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD); // No fixed IP: took 1.6 sec longer than my DHCP.
  
  configTime(0, 0, TIME_NTPSERVER_1, TIME_NTPSERVER_2);
  setenv("TZ", "CET-1CEST,M3.5.0/2,M10.5.0/3", 0);

  Serial.printf("%u: ConnectToWiFi\n", millis());
}

void GoToSleep() {
  WiFi.disconnect(true);
  delay(1);
  WiFi.mode(WIFI_OFF);
  WiFi.forceSleepBegin();
  delay(5);

  Serial.printf("%u: Going to sleep\n", millis());
  Serial.flush();
  // WAKE_RF_DISABLED to keep the WiFi radio disabled when we wake up
  ESP.deepSleep( SLEEPTIME, RF_DISABLED );
}

void setup() {
  // Set WiFi Off
  WiFi.mode(WIFI_OFF);
  WiFi.forceSleepBegin();
  delay(1);

  // Serial
  Serial.begin(115200);
  Serial.println();
  //Serial.printf("%u: \nHello world!\n", millis() );

  // WiFi
  static WiFiEventHandler e1, e2, e3; 

  // Other code. For example: Serial.begin(115200);

  // WiFi
  e1 = WiFi.onStationModeGotIP(onSTAGotIP); 
  e2 = WiFi.onStationModeConnected(onSTAConnected); 
  e3 = WiFi.onStationModeDisconnected(onSTADisconnected); 
  
  connectToWiFi();

  // Other code 
} 

void loop() {
  // Use WiFi as client, server, etc
  if (WiFi.status() == WL_CONNECTED) {
    
    //Serial.println("Doing stuff");
    while (time(nullptr) < 24 * 3600) delay(1);
    time_t tnow = time(nullptr);
    Serial.print(String(ctime(&tnow)));

    GoToSleep();
  }
}