Reducing WiFi power consumption on ESP8266, part 3

7 thoughts on “Reducing WiFi power consumption on ESP8266, part 3”

1. Thank You, man!
   Your article was very helpfull for me. I wanted use for powered ESP from garden solar light. I had problem with using only one solar cell. When I applicated your solution, rasantelly fall consumed current, and now enough for powering!
   Again thanks, many success in future projects!

   1. Happy to help. I’m just about to start a solar powered project on one of these chips myself. The idea is to let the solar cell charge my batteries enough while the ESP sleeps to both power the device when it wakes up as well as through the night.
      Hopefully I will have enough sun during the day to get results as good as yours 🙂

2. Hello,

   Thanks for these tutos … but unfortunately, I missed something 🙁

   Here my code :

   #include
   #include /* https://pubsubclient.knolleary.net/api.html */

   #include “Maison.h” /* WiFi settings */
   #define LED_BUILTIN 2

   #define MQTT_PUBTOPIC “TestPub”
   #define MQTT_CLIENT “TestWiFiDS”

   IPAddress adr_ip(192, 168, 0, 17);
   IPAddress adr_gateway(192, 168, 0, 10);
   IPAddress adr_dns(192, 168, 0, 3);

   WiFiClient clientWiFi;
   PubSubClient clientMQTT(clientWiFi);

   void connexion_WiFi(){
   WiFi.forceSleepWake(); // Réveil le WiFi
   delay(10);
   Serial.println(“Connexion WiFi”);

   WiFi.persistent( false );

   WiFi.mode(WIFI_STA);
   WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
   while(WiFi.status() != WL_CONNECTED){
   delay(500);
   Serial.print(“.”);
   }

   Serial.print(“ok : adresse “);
   Serial.println(WiFi.localIP());
   }

   void Connexion_MQTT(){
   digitalWrite(LED_BUILTIN, LOW);
   Serial.println(“Connexion MQTT”);
   while(!clientMQTT.connected()){
   if(clientMQTT.connect(MQTT_CLIENT)){
   Serial.println(“connecté”);
   break;
   } else {
   Serial.print(“Echec, rc:”);
   Serial.println(clientMQTT.state());
   delay(1000); // Test dans 1 seconde
   }
   }
   digitalWrite(LED_BUILTIN, HIGH);
   }

   void setup() {
   long debut = millis(); // Calcul du temps de connexion

   /*
   * Init hardward
   */
   Serial.begin(115200); // debug
   pinMode(LED_BUILTIN, OUTPUT); // La LED est allumée pendant la recherche de WiFi

   /*
   * Init WiFi
   */
   WiFi.config(adr_ip, adr_gateway, adr_dns); // Service de base du réseau
   connexion_WiFi();

   /*
   * Envoi du message MQTT
   */
   clientMQTT.setServer(BROKER_HOST, BROKER_PORT);
   Connexion_MQTT();

   long q=millis();
   clientMQTT.publish(MQTT_PUBTOPIC, String( q-debut ).c_str());
   Serial.println( String( q-debut ).c_str() );

   WiFi.disconnect( true ); // Explicitement désactive le WiFi
   delay( 1 );
   ESP.deepSleep(10e6, WAKE_RF_DISABLED);
   }

   void loop() {
   }

   But at wakeup, my ESP-12 stays forever in loop
   while(WiFi.status() != WL_CONNECTED){
   delay(500);
   Serial.print(“.”);
   }

   So it seems the WiFi is never connected.

   I think it’s a stupid mistake … but it drives me nuts and I can’t where I’m wrong.
   Any idea ?

   Thanks

   1. Bonjour.

      I’ve compiled your program for one of my own modules here and was able to reproduce exactly the same problem here.
      It is easily fixed, though, by adding the following lines to the beginning of your setup() function:

      WiFi.mode( WIFI_OFF );
WiFi.forceSleepBegin();
delay( 1 );

      It looks like my code does not initialise the WiFi radio properly, otherwise. My process was quite iterative, so each optimisation step was building on what came before, and it looks like the WiFi.forceSleepWake() and WiFi.mode() calls depend on this initialisation to happen first.

      One other thing that I usually do is to place a timeout on the WiFi connection, so that if a connection has not been established by a certain number of loops, I will reset the module. (Or send it back to sleep, depending on what is most suitable for the situation)

      1. Thanks for your informations!
         I will try it on my esp, but i don’t know if it’s possible to activate and deactivate the wifi in a loop like a timer during only a period of time like…each 2 minutes between my first action and my last action, i want to use the wifi to retrieve data from a mqtt only during a period of time

         1. Hi Rudy.
            THat should be possible. I have an example sketch here which keeps the WiFi disabled until I need it, then I enable the WiFi, do what needs to be done and then disable it again, without going back to deep sleep. After a minute, the loop repeats, the WiFi is enabled again, and so on.

            I’m posting it below, so you can see what I am talking about.
            
#include "test.h"

            #include
            #include

            #include

            const char* WLAN_SSID = "XXXXXXXX";
            const char* WLAN_PASSWD = "????????";

            int loops = 0;

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

            Serial.begin( 115200 );

            while ( !Serial );

            Serial.println( "Booted, and have disabled WiFi radio" );
            }

            void loop() {
            loops++;
            Serial.println ( "Entering loop()" );

            Serial.println ( "Enabling WiFi" );
            WiFi.forceSleepWake();
            delay( 1 );
            WiFi.persistent( true );
            WiFi.mode( WIFI_STA );

            WiFi.begin( WLAN_SSID, WLAN_PASSWD );

            int retries = 0;
            int wifiStatus = WiFi.status();
            while ( wifiStatus != WL_CONNECTED )
            {
            retries++;
            if( retries == 300 )
            {
            Serial.println( "No connection after 300 steps, powercycling the WiFi radio. I have seen this work when the connection is unstable" );
            WiFi.disconnect();
            delay( 10 );
            WiFi.forceSleepBegin();
            delay( 10 );
            WiFi.forceSleepWake();
            delay( 10 );
            WiFi.begin( WLAN_SSID, WLAN_PASSWD );
            }
            if ( retries == 600 )
            {
            WiFi.disconnect( true );
            delay( 1 );
            WiFi.mode( WIFI_OFF );
            WiFi.forceSleepBegin();
            delay( 10 );

            if( loops == 3 )
            {
            Serial.println( "That was 3 loops, still no connection so let's go to deep sleep for 2 minutes" );
            Serial.flush();
            ESP.deepSleep( 120000000, WAKE_RF_DISABLED );
            }
            else
            {
            Serial.println( "No connection after 600 steps. WiFi connection failed, disabled WiFi and waiting for a minute" );
            }

            delay( 60000 );
            return;
            }
            delay( 50 );
            wifiStatus = WiFi.status();
            }
            Serial.print( "Connected to " );
            Serial.println( WLAN_SSID );
            Serial.print( "Assigned IP address: " );
            Serial.println( WiFi.localIP() );
            Serial.println( "WiFi connection successful, waiting for 10 seconds" );
            delay( 10000 );

            MQTT_uploadToServer();

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

            if( loops == 3 )
            {
            Serial.println( "That was 3 loops, so let's go to deep sleep for 2 minutes" );
            Serial.flush();
            ESP.deepSleep( 120000000, WAKE_RF_DISABLED );
            }
            else
            {
            Serial.println( "All done, disabled WiFi and will wait for a minute." );
            delay( 60000 );
            }
            }

            void MQTT_uploadToServer()
            {
            WiFiClient client;
            float temp = -500; // Use this as a flag, as -500 degrees is physically impossible, it is below absolute zero
            int8_t ret;

            Adafruit_MQTT_Client mqtt( &client, MQTT_SERVER, MQTT_SERVERPORT, MQTT_USERNAME, MQTT_PASSWD );
            Adafruit_MQTT_Publish publish_temp = Adafruit_MQTT_Publish( &mqtt, MQTT_USERNAME "/feeds/" MQTT_NAME "/temp", MQTT_QOS_0, 1 );

            Serial.println("Connecting to MQTT... ");

            uint8_t retries = 3;
            while ((ret = mqtt.connect()) != 0) { // connect will return 0 for connected
            Serial.println(mqtt.connectErrorString(ret));
            Serial.println("Retrying MQTT connection in 5 seconds...");

            mqtt.disconnect();
            delay(5000); // wait 5 seconds
            retries--;
            if (retries == 0) {
            // basically just hang around and wait for the watchdog to come and eat us.
            while (1);
            }
            }
            Serial.println( "MQTT Connected!" );
            Serial.println( "Sending MQTT message" );
            publish_temp.publish( temp );

            delay( 50 );
mqtt.disconnect();
Serial.println("Disconnected from MQTT");
}


3. Hi ebakke,
   I am doing pretty the same, designing a WIFI temperature / humidity sensor to report to a server (another ESP system)
   I followed basically your advice and get a wake time of unbelivable 200ms to connect to the server, read out the HTU21 and send the data via UDP. Reading the sensor is done while connecting.

   However, I go to deep sleep with WAKE_RFCAL and omit the forceSleep calls.
   The 200ms are measured from the begin of setup to the point where I go back to sleep.

   The ESP needs another 300ms or so from reset until it enters setup, so I have an overall on-time of about 500ms consuming an average of 70mA -> tis makes 10µAh per measurement.
   I also tried your version with going to sleept with WAKE_RF_DISABLED and enabling WIFI again in setup so the first 300ms only consume about 13mA. Then however the connection takes 400ms, so there is no advantage in this.

   I have no idea, why my connection is so much faster – probably my router is connecting faster (a AVM fritz!box) or the ESP I am using has some newer firmware or what ever. When sleeping I measure about 18µA including the HTU21 – so I am sure the device is really in deep sleep.

   As a board I am using a modified Wemos D1 mini with a split up 3.3V power source so the USB system does not draw any power when not active.

   Rainer

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