Temperature upload over MQTT using ESP8266 and DHT22 sensor

Introduction

ThingsBoard is an open-source server-side platform that allows you to monitor and control IoT devices. It is free for both personal and commercial usage and you can deploy it anywhere. If this is your first experience with the platform we recommend to review what-is-thingsboard page and getting-started guide.

This sample application performs collection of temperature and humidity values produced by DHT22 sensor and further visualization on the real-time web dashboard. Collected data is pushed via MQTT to ThingsBoard server for storage and visualization. The purpose of this application is to demonstrate ThingsBoard data collection API and visualization capabilities.

The DHT22 sensor is connected to ESP8266. ESP8266 offers a complete and self-contained Wi-Fi networking solution. ESP8266 push data to ThingsBoard server via MQTT protocol by using PubSubClient library for Arduino. Data is visualized using built-in customizable dashboard. The application that is running on ESP8266 is written using Arduino SDK which is quite simple and easy to understand.

The video below demonstrates the final result of this tutorial.













Once you complete this sample/tutorial, you will see your sensor data on the following dashboard.

Prerequisites

You will need to have ThingsBoard server up and running. Use either Live Demo or Installation Guide to install ThingsBoard.

List of hardware and pinouts

USB to TTL With DTR & RTS Or Without DTR & RTS

Resistor (between 4.7K and 10K)

Breadboard

2 female-to-female jumper wires

10 female-to-male jumper wires

3 male-to-male jumper wire

3.3V power source (for example 2 AA batteries)

Wiring schemes

Programming/flashing schema

ESP8266 Pin USB-TTL Pin ESP8266 VCC USB-TTL VCC +3.3V ESP8266 CH_PD USB-TTL VCC +3.3V ESP8266 GND (-) USB-TTL GND ESP8266 GPIO 0 USB-TTL GND ESP8266 RX USB-TTL TX ESP8266 TX USB-TTL RX

DHT-22 Pin ESP8266 Pin DHT-22 Data ESP8266 GPIO 2

DHT-22 Pin USB-TTL Pin DHT-22 VCC USB-TTL VCC +3.3V DHT-22 GND (-) USB-TTL GND

Finally, place a resistor (between 4.7K and 10K) between pin number 1 and 2 of the DHT sensor.

The following picture summarizes the connections for this project in programming/debug mode:

Final schema (Battery Powered)

ESP8266 Pin 3.3V power source ESP8266 VCC VCC+ ESP8266 CH_PD VCC+ ESP8266 GND (-) VCC-

DHT-22 Pin ESP8266 Pin DHT-22 Data ESP8266 GPIO 2

DHT-22 Pin 3.3V power source DHT-22 VCC VCC+ DHT-22 GND (-) VCC-

The final picture:

ThingsBoard configuration

Note ThingsBoard configuration steps are necessary only in case of local ThingsBoard installation. If you are using Live Demo instance all entities are pre-configured for your demo account. However, we recommend reviewing this steps because you will still need to get device access token to send requests to ThingsBoard.

Provision your device

This step contains instructions that are necessary to connect your device to ThingsBoard.

Open ThingsBoard Web UI (http://localhost:8080) in browser and login as tenant administrator

Go to “Devices” section. Click “+” button and create a device with the name “ESP8266 Demo Device”.

Once device created, open its details and click “Manage credentials”. Copy auto-generated access token from the “Access token” field. Please save this device token. It will be referred to later as $ACCESS_TOKEN.

Click “Copy Device ID” in device details to copy your device id to the clipboard. Paste your device id to some place, this value will be used in further steps.

Provision your dashboard

Download the dashboard file using this link. Use import/export instructions to import the dashboard to your ThingsBoard instance.

Programming the ESP8266

Step 1. ESP8266 and Arduino IDE setup.

In order to start programming ESP8266 device, you will need Arduino IDE installed and all related software.

Download and install Arduino IDE.

After starting Arduino IDE, open the preferences from the ‘file’ menu.

Paste the following URL to the “Additional board managers URL”: http://arduino.esp8266.com/stable/package_esp8266com_index.json

Close the screen by clicking the OK button.

Now we can add the board ESP8266 using the board manager.

In the menu tools, click on the menu option Board: “Most likely Arduino UNO”. There you will find the first option “Board Manager”.

Type in the search bar the 3 letters ESP. Locate and click on “esp8266 by ESP8266 Community”. Click on install and wait for a minute to download the board.

Note that this tutorial was tested with the “esp8266 by ESP8266 Community” version 2.3.0.

In the menu Tools “Board “Most likely Arduino UNO” three new boards are added.

Select “Generic ESP8266 Module”.

Prepare your hardware according to the Programming/flashing schema. Connect USB-TTL adapter with PC.

In the menu Tools, select the corresponding port of the USB-TTL adapter. Open the serial monitor (by pressing CTRL-Shift-M or from the menu Tools). Set the key emulation to “Both NL & CR” and the speed to 115200 baud. This can be set in the bottom of terminal screen.

Step 2. Install Arduino libraries.

Open Arduino IDE and go to Sketch -> Include Library -> Manage Libraries. Find and install the following libraries:

Note that this tutorial was tested with the following versions of the libraries:

PubSubClient 2.6

Adafruit Unified Sensor 1.0.2

DHT sensor library 1.3.0

Arduino ThingsBoard SDK 0.4

ArduinoJSON 6.10.1

Arduino Http Client 0.4.0

Step 3. Prepare and upload a sketch.

Download and open esp8266-dht-mqtt.ino sketch.

Note You need to edit following constants and variables in the sketch:

WIFI_AP - name of your access point

WIFI_PASSWORD - access point password

TOKEN - the $ACCESS_TOKEN from ThingsBoard configuration step.

from ThingsBoard configuration step. thingsboardServer - ThingsBoard HOST/IP address that is accessible within your wifi network. Specify “demo.thingsboard.io” if you are using live demo server.

esp8266-dht-mqtt.ino resources/esp8266-dht-mqtt.ino #include "DHT.h" #include <ESP8266WiFi.h> #include <ThingsBoard.h> #define WIFI_AP "YOUR_WIFI_AP" #define WIFI_PASSWORD "YOUR_WIFI_PASSWORD" #define TOKEN "ESP8266_DEMO_TOKEN" // DHT #define DHTPIN 2 #define DHTTYPE DHT22 char thingsboardServer [] = "YOUR_THINGSBOARD_HOST_OR_IP" ; WiFiClient wifiClient ; // Initialize DHT sensor. DHT dht ( DHTPIN , DHTTYPE ); ThingsBoard tb ( wifiClient ); int status = WL_IDLE_STATUS ; unsigned long lastSend ; void setup () { Serial . begin ( 115200 ); dht . begin (); delay ( 10 ); InitWiFi (); lastSend = 0 ; } void loop () { if ( ! tb . connected () ) { reconnect (); } if ( millis () - lastSend > 1000 ) { // Update and send only after 1 seconds getAndSendTemperatureAndHumidityData (); lastSend = millis (); } tb . loop (); } void getAndSendTemperatureAndHumidityData () { Serial . println ( "Collecting temperature data." ); // Reading temperature or humidity takes about 250 milliseconds! float humidity = dht . readHumidity (); // Read temperature as Celsius (the default) float temperature = dht . readTemperature (); // Check if any reads failed and exit early (to try again). if ( isnan ( humidity ) || isnan ( temperature )) { Serial . println ( "Failed to read from DHT sensor!" ); return ; } Serial . println ( "Sending data to ThingsBoard:" ); Serial . print ( "Humidity: " ); Serial . print ( humidity ); Serial . print ( " % \t " ); Serial . print ( "Temperature: " ); Serial . print ( temperature ); Serial . println ( " *C " ); tb . sendTelemetryFloat ( "temperature" , temperature ); tb . sendTelemetryFloat ( "humidity" , humidity ); } void InitWiFi () { Serial . println ( "Connecting to AP ..." ); // attempt to connect to WiFi network WiFi . begin ( WIFI_AP , WIFI_PASSWORD ); while ( WiFi . status () != WL_CONNECTED ) { delay ( 500 ); Serial . print ( "." ); } Serial . println ( "Connected to AP" ); } void reconnect () { // Loop until we're reconnected while ( ! tb . connected ()) { status = WiFi . status (); if ( status != WL_CONNECTED ) { WiFi . begin ( WIFI_AP , WIFI_PASSWORD ); while ( WiFi . status () != WL_CONNECTED ) { delay ( 500 ); Serial . print ( "." ); } Serial . println ( "Connected to AP" ); } Serial . print ( "Connecting to ThingsBoard node ..." ); if ( tb . connect ( thingsboardServer , TOKEN ) ) { Serial . println ( "[DONE]" ); } else { Serial . print ( "[FAILED]" ); Serial . println ( " : retrying in 5 seconds]" ); // Wait 5 seconds before retrying delay ( 5000 ); } } }

Connect USB-TTL adapter to PC and select the corresponding port in Arduino IDE. Compile and Upload your sketch to the device using “Upload” button.

After application will be uploaded and started it will try to connect to ThingsBoard node using mqtt client and upload “temperature” and “humidity” timeseries data once per second.

Autonomous operation

When you have uploaded the sketch, you may remove all the wires required for uploading including USB-TTL adapter and connect your ESP8266 and DHT sensor directly to the power source according to the Final wiring schema.

Troubleshooting

In order to perform troubleshooting, you should assemble your hardware according to the Programming/flashing schema. Then connect USB-TTL adapter with PC and select port of the USB-TTL adapter in Arduino IDE. Finally, open “Serial Monitor” in order to view debug information produced by serial output.

Data visualization

Finally, open ThingsBoard Web UI. You can access this dashboard by logging in as a tenant administrator. Use:

in case of local ThingsBoard installation.

Go to “Devices” section and locate “ESP8266 Demo Device”, open device details and switch to “Latest telemetry” tab. If all is configured correctly you should be able to see latest values of “temperature” and “humidity” in the table.

After, open “Dashboards” section then locate and open “ESP8266 DHT22: Temperature & Humidity Demo Dashboard”. As a result, you will see two digital gauges and two time-series charts displaying temperature and humidity level (similar to dashboard image in the introduction).

See also

Browse other samples or explore guides related to main ThingsBoard features:

Your feedback

Don’t hesitate to star ThingsBoard on github to help us spread the word. If you have any questions about this sample - post it on the issues.

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