DHT11 locally on a ESP8266 MQTT Gateway

Yeitso

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.
 *
 *******************************
 *
 * REVISION HISTORY
 * Version 1.0 - Henrik Ekblad
 *
 * DESCRIPTION
 * 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_MQTT_CLIENT
#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
#define MY_INCLUSION_MODE_FEATURE
// Enable Inclusion mode button on gateway
#define MY_INCLUSION_BUTTON_FEATURE
// Set inclusion mode duration (in seconds)
#define MY_INCLUSION_MODE_DURATION 60
// Digital pin used for inclusion mode button
#define MY_INCLUSION_MODE_BUTTON_PIN  1

// Set blinking period
#define MY_DEFAULT_LED_BLINK_PERIOD 300

// 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)
  wait(dht.getMinimumSamplingPeriod());
}


void loop()
{
  // Force reading sensor, so it works also after sleep()
  dht.readSensor(true);

  // 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: ");
    Serial.println(temperature);
    #endif
  } else {
    // Increase no update counter if the temperature stayed the same
    nNoUpdatesTemp++;
  }

  // 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: ");
    Serial.println(humidity);
    #endif
  } else {
    // Increase no update counter if the humidity stayed the same
    nNoUpdatesHum++;
  }

  // Sleep for a while to save energy
  wait(UPDATE_INTERVAL);
}

Yeitso

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.

Yveaux

@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/

Yeitso

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

DHT11 locally on a ESP8266 MQTT Gateway

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