DHT11 locally on a ESP8266 MQTT Gateway

  • Hi

    Im trying to get my ESP8266 MQTT Gateway with a locally attached DHT11 sensor to work and I almost got it.

    My problem is that the temp im reading is waaaay off. See screenshot

    Serial monitor

    Any help would be appreciated.

    The sketch im using is this:

     * The MySensors Arduino library handles the wireless radio link and protocol
     * between your home built sensors/actuators and HA controller of choice.
     * The sensors forms a self healing radio network with optional repeaters. Each
     * repeater and gateway builds a routing tables in EEPROM which keeps track of the
     * network topology allowing messages to be routed to nodes.
     * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
     * Copyright (C) 2013-2015 Sensnology AB
     * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
     * Documentation: http://www.mysensors.org
     * Support Forum: http://forum.mysensors.org
     * This program is free software; you can redistribute it and/or
     * modify it under the terms of the GNU General Public License
     * version 2 as published by the Free Software Foundation.
     * Version 1.0 - Henrik Ekblad
     * The ESP8266 MQTT gateway sends radio network (or locally attached sensors) data to your MQTT broker.
     * The node also listens to MY_MQTT_TOPIC_PREFIX and sends out those messages to the radio network
     * LED purposes:
     * - To use the feature, uncomment any of the MY_DEFAULT_xx_LED_PINs in your sketch
     * - RX (green) - blink fast on radio message recieved. In inclusion mode will blink fast only on presentation recieved
     * - TX (yellow) - blink fast on radio message transmitted. In inclusion mode will blink slowly
     * - ERR (red) - fast blink on error during transmission error or recieve crc error
     * See http://www.mysensors.org/build/esp8266_gateway for wiring instructions.
     * nRF24L01+  ESP8266
     * VCC        VCC
     * CE         GPIO4
     * CSN/CS     GPIO15
     * SCK        GPIO14
     * MISO       GPIO12
     * MOSI       GPIO13
     * Not all ESP8266 modules have all pins available on their external interface.
     * This code has been tested on an ESP-12 module.
     * The ESP8266 requires a certain pin configuration to download code, and another one to run code:
     * - Connect REST (reset) via 10K pullup resistor to VCC, and via switch to GND ('reset switch')
     * - Connect GPIO15 via 10K pulldown resistor to GND
     * - Connect CH_PD via 10K resistor to VCC
     * - Connect GPIO2 via 10K resistor to VCC
     * - Connect GPIO0 via 10K resistor to VCC, and via switch to GND ('bootload switch')
      * Inclusion mode button:
     * - Connect GPIO5 via switch to GND ('inclusion switch')
     * Hardware SHA204 signing is currently not supported!
     * Make sure to fill in your ssid and WiFi password below for ssid & pass.
    // Enable debug prints to serial monitor
    #define MY_DEBUG
    // Use a bit lower baudrate for serial prints on ESP8266 than default in MyConfig.h
    #define MY_BAUD_RATE 9600
    // Enables and select radio type (if attached)
    //#define MY_RADIO_NRF24
    #define MY_RADIO_RFM69
    #define MY_GATEWAY_ESP8266
    // Set this node's subscribe and publish topic prefix
    #define MY_MQTT_PUBLISH_TOPIC_PREFIX "mygateway1-out"
    #define MY_MQTT_SUBSCRIBE_TOPIC_PREFIX "mygateway1-in"
    // Set MQTT client id
    #define MY_MQTT_CLIENT_ID "mysensors-1"
    // Enable these if your MQTT broker requires usenrame/password
    //#define MY_MQTT_USER "username"
    //#define MY_MQTT_PASSWORD "password"
    // Set WIFI SSID and password
    #define MY_ESP8266_SSID "SSID"
    #define MY_ESP8266_PASSWORD "PASSWORD"
    // Set the hostname for the WiFi Client. This is the hostname
    // it will pass to the DHCP server if not static.
    #define MY_ESP8266_HOSTNAME "mqtt-sensor-gateway"
    // Enable MY_IP_ADDRESS here if you want a static ip address (no DHCP)
    //#define MY_IP_ADDRESS 192,168,178,87
    // If using static ip you need to define Gateway and Subnet address as well
    //#define MY_IP_GATEWAY_ADDRESS 192,168,178,1
    //#define MY_IP_SUBNET_ADDRESS 255,255,255,0
    // MQTT broker ip address.
    #define MY_CONTROLLER_IP_ADDRESS 192, 168, 1 , 87
    // The MQTT broker port to to open
    #define MY_PORT 1883
     #include <SPI.h>
     #include <ESP8266WiFi.h>
     #include <MySensors.h>
     #include <DHT.h>
    //DHT11 stuff, This node on MQTT mygateway1-out/X/1/1/0/0 for temperature and mygateway1-out/X/0/1/0/1 for humidity
    #define DHT_DATA_PIN 5
    #define SENSOR_TEMP_OFFSET 0
    static const uint8_t FORCE_UPDATE_N_READS = 10;
    static const uint64_t UPDATE_INTERVAL = 2000;
    #define CHILD_ID_HUM 0
    #define CHILD_ID_TEMP 1
    float lastTemp;
    float lastHum;
    uint8_t nNoUpdatesTemp;
    uint8_t nNoUpdatesHum;
    bool metric = true;
    MyMessage msgHum(CHILD_ID_HUM, V_HUM);
    MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);
    DHT dht;
    // Enable inclusion mode
    // Enable Inclusion mode button on gateway
    // Set inclusion mode duration (in seconds)
    // Digital pin used for inclusion mode button
    // Set blinking period
    // Flash leds on rx/tx/err
    #define MY_DEFAULT_ERR_LED_PIN 16  // Error led pin
    #define MY_DEFAULT_RX_LED_PIN  16  // Receive led pin
    #define MY_DEFAULT_TX_LED_PIN  16  // the PCB, on board LED
    void presentation()
      // Send the sketch version information to the gateway
      sendSketchInfo("TemperatureAndHumidity", "1.1");
      // Register all sensors to gw (they will be created as child devices)
      present(CHILD_ID_HUM, S_HUM);
      present(CHILD_ID_TEMP, S_TEMP);
      metric = getConfig().isMetric;
    void setup()
      dht.setup(DHT_DATA_PIN); // set data pin of DHT sensor
      if (UPDATE_INTERVAL <= dht.getMinimumSamplingPeriod()) {
        Serial.println("Warning: UPDATE_INTERVAL is smaller than supported by the sensor!");
      // Sleep for the time of the minimum sampling period to give the sensor time to power up
      // (otherwise, timeout errors might occure for the first reading)
    void loop()
      // Force reading sensor, so it works also after sleep()
      // Get temperature from DHT library
      float temperature = dht.getTemperature();
      if (isnan(temperature)) {
        Serial.println("Failed reading temperature from DHT!");
      } else if (temperature != lastTemp || nNoUpdatesTemp == FORCE_UPDATE_N_READS) {
        // Only send temperature if it changed since the last measurement or if we didn't send an update for n times
        lastTemp = temperature;
        if (!metric) {
          temperature = dht.toFahrenheit(temperature);
        // Reset no updates counter
        nNoUpdatesTemp = 0;
        temperature += SENSOR_TEMP_OFFSET;
        send(msgTemp.set(temperature, 1));
        #ifdef MY_DEBUG
        Serial.print("T: ");
      } else {
        // Increase no update counter if the temperature stayed the same
      // Get humidity from DHT library
      float humidity = dht.getHumidity();
      if (isnan(humidity)) {
        Serial.println("Failed reading humidity from DHT");
      } else if (humidity != lastHum || nNoUpdatesHum == FORCE_UPDATE_N_READS) {
        // Only send humidity if it changed since the last measurement or if we didn't send an update for n times
        lastHum = humidity;
        // Reset no updates counter
        nNoUpdatesHum = 0;
        send(msgHum.set(humidity, 1));
        #ifdef MY_DEBUG
        Serial.print("H: ");
      } else {
        // Increase no update counter if the humidity stayed the same
      // Sleep for a while to save energy

  • I can also add that the room in measuring is quite cold. Like about 13-16 degrees so its not only a decimal error.

    I might have a faulty DHT11 module but im not shure.

  • Mod

    @Yeitso What DHT11 library are you using? It might not be compatinly with ESP8266...
    You could try the library describved here: https://techtutorialsx.wordpress.com/2016/04/24/esp8266-read-dht11-measurements/

  • Yeah im gonna try to switch to adafruits lib. Atm im using the one from mysensors.