Learn how to publish DS18B20 temperature readings via MQTT with the ESP32 to any platform that supports MQTT or any request temperature readings from the DS18B20 sensor. The readings are published in the esp32/ds18b20/temperature topic;
- Node-RED is subscribed to the esp3232 add-on installed.
MQTT Broker
To use MQTT, you need a broker. We’ll be using Mosquitto broker installed on a Raspberry Pi. Read How to Install Mosquitto Broker on Raspberry Pi.
You can use any other MQTT broker, including a cloud MQTT broker. We’ll show you how to do that in the code later on.
If you’re not familiar with MQTT make sure you read our introductory tutorial: What is MQTT and How It Works.
MQTT Libraries
To use MQTT with the ESP32 we’ll use the Async MQTT Client Library.
Installing the Async MQTT Client Library
- Click here to download the Async MQTT client library. You should have a .zip folder in your Downloads folder
- Unzip the .zip folder and you should get async-mqtt-client-master folder
- Rename your folder from
async-mqtt-client-masterto async_mqtt_client
- Move the async_mqtt_client folder to your Arduino IDE installation libraries folder
- Finally, re-open your Arduino IDE
Alternatively, you can go to Sketch > Include Library > Add . ZIP library and select the library you’ve just downloaded.
Installing the Async TCP Library
To use MQTT with the ESP, you also need the Async TCP library.
- Click here to download the Async TCP client32 DS18B20 Temperature Sensor with Arduino IDE (Single, Multiple, Web Server).
Parts Required
For this tutorial you need the following parts:
- ESP32 (read Best ESP32 development boards)
- DS18B20 Temperature Sensor – DS18B20 with ESP32 Guide
- 4.7k Ohm resistor
- Raspberry Pi board (read Best Raspberry Pi Starter Kits)
- MicroSD Card – 16GB Class10
- Raspberry Pi Power Supply (5V 2.5A)
- Jumper wires
- Breadboard
You can use the preceding links or go directly to MakerAdvisor.com/tools to find all the parts for your projects at the best price!
Schematic Diagram
Wire the DS18B20 to the ESP32 as shown in the following schematic diagram with the DS18B20 data pin connected to GPIO 4.
Code
Copy the following code to your Arduino IDE. To make it work for you, you need to insert your network credentials as well as the MQTT broker> extern "C" { #include "freertos/FreeRTOS.h" #include "freertos/timers.h" } #include <AsyncMqttClient.h> #include <OneWire.h> #include <DallasTemperature.h> #define WIFI_SSID "REPLACE_WITH_YOUR_SSID" #define WIFI_PASSWORD "REPLACE_WITH_YOUR_PASSWORD" // Raspberry Pi Mosquitto MQTT Broker #define MQTT_HOST IPAddress(192, 168, 1, XXX) // For a cloud MQTT broker, type the domain name //#define MQTT_HOST "example.com" #define MQTT_PORT 1883 // Temperature MQTT Topic #define MQTT_PUB_TEMP "esp32/ds18b20/temperature" //); // Temperature value float temp;; } } void onMqttConnect(bool sessionPresent) { Serial.println("Connected to MQTT."); Serial.print("Session present: "); Serial.println(sessionPresent); } void onMqttDisconnect(AsyncMqttClientDisconnectReason reason) { Serial.println("Disconnected from MQTT."); if (WiFi.isConnected()) { xTimerStart(mqttReconnectTimer, 0); } } /*void onMqttSubscribe(uint16_t packetId, uint8_t qos) { Serial.println("Subscribe acknowledged."); Serial.print(" packetId: "); Serial.println(packetId); Serial.print(" qos: "); Serial.println(qos); } void onMqttUnsubscribe(uint16_t packetId) { Serial.println("Unsubscribe acknowledged."); Serial.print(" packetId: "); Serial.println(packetId); }*/ void onMqttPublish(uint16_t packetId) { Serial.println("Publish acknowledged."); Serial.print(" packetId: "); Serial.println(packetId); } void setup() { // Start the DS18B20 sensor sensors.begin(); Serial.begin(115200); Serial.println(); Serial.println();)); WiFi.onEvent(WiFiEvent);); // If your broker requires authentication (username and password), set them below //mqttClient.setCredentials("REPlACE_WITH_YOUR_USER", "REPLACE_WITH_YOUR_PASSWORD"); connectToWifi(); } void loop() {); // Temperature in Fahrenheit degrees //temp = sensors.getTempFByIndex(0); // Publish an MQTT message on topic esp32/ds18b20/temperature uint16_t packetIdPub1 = mqttClient.publish(MQTT_PUB_TEMP, 1, true, String(temp).c_str()); Serial.printf("Publishing on topic %s at QoS 1, packetId: ", MQTT_PUB_TEMP); Serial.println(packetIdPub1); Serial.printf("Message: %.2f /n", sensors.getTempCByIndex(0)); } }
How the Code Works
The following section imports all the required libraries.
#include <WiFi.h> extern "C" { #include "freertos/FreeRTOS.h" #include "freertos/timers.h" } #include <AsyncMqttClient.h> #include <OneWire.h> #include <DallasTemperature.h>
Include your network credentials on the following lines.
#define WIFI_SSID "REPLACE_WITH_YOUR_SSID" #define WIFI_PASSWORD "REPLACE_WITH_YOUR_PASSWORD"
Insert the Raspberry Pi IP address, so that the ESP32 connects to your broker.
#define MQTT_HOST IPAddress(192, 168, 1, 106)
If you’re using a cloud MQTT broker, insert the broker domain name, for example:
#define MQTT_HOST "example.com"
Define the MQTT port.
#define MQTT_PORT 1883
We’ll publish the temperature on the esp32/ds18b20/temperature topic. If you want to change the topic, change it on the following line.
#define MQTT_PUB_TEMP "esp32/ds18b20/temperature"
You can create more topics if you want.
Setup your DS18B20 on the following lines. In our case, it is connected to GPIO 4. You can connect it to any other GPIO.
//_t wifiReconnectTimer;
Then, create some auxiliary timer variables to publish the readings every 10 seconds. You can change the delay time on the interval variable.
unsigned long previousMillis = 0; // Stores last time temperature was published const long interval = 10000; // Interval at which to publish sensor readings
MQTT functions: connect to Wi-Fi, connect to MQTT, and Wi-Fi events
We haven’t added any comments to the functions defined in the next code section. Those functions come with the Async Mqtt Client library. The function’s names are pretty self-explanatory.
For example, the connectToWifi() connects your ESP connects to the broker, it automatically calls the onMqttConnect() function, and so on.);
Broker Authentication
If your broker requires authentication, uncomment the following line and insert your credentials (username and password).
mqttClient.setCredentials("REPlACE_WITH_YOUR_USER", "REPLACE_WITH_YOUR_PASSWORD");
Finally, connect to Wi-Fi.
connectToWifi();
loop()
In the loop(), you create a timer that will allow you to publish new temperature readings in the esp32/d18b20/temperature topic every 10 seconds.);
If you prefer the temperature in Fahrenheit, uncomment the following line:
//temp = sensors.getTempFByIndex(0);
Learn more about the DS18B20 temperature sensor: ESP32 with DS18B20 Temperature Sensor Guide.().
Basically, use the publish() method on the mqttClient object to publish data on a topic. The publish() method accepts the following arguments, in order:
- MQTT topic (const char*)
- QoS (uint8_t): quality of service – it can be 0, 1 or 2
- retain flag (bool): retain flag
- payload (const char*)
The QoS (quality of service) is a way to guarantee that the message is delivered. It can be one of the following levels:
- 0: the message will be delivered once or not at all. The message is not acknowledged. There is no possibility of duplicated messages;
- 1: the message will be delivered at least once, but may be delivered more than once;
- 2: the message is always delivered exactly once;
Uploading the code
With your Raspberry Pi powered on and running the Mosquitto MQTT broker, upload the code to your ESP32.
Open the Serial Monitor at a baud rate of 115200 and you’ll see that the ESP32 starts publishing messages.
Preparing Node-RED Dashboard
The ESP32 is publishing temperature readings every 10 seconds on the esp32:
The Server field refers to the MQTT broker. In our case, the MQTT broker is the Raspberry Pi, so it is set to localhost:1883. If you’re using a Cloud MQTT broker, you should change that field. Insert the topic you want to be subscribed to and the QoS./ds18b20/temperature","qos":"1","datatype":"auto","broker":"8db3fac0.99dd48","x":380,"y":280,"wires":[["3042e15e.80a4ee","4c53cb0f.3e6084"]]},{"id":"3042e15e.80a4ee","type":"ui_gauge","z":"b01416d3.f69f38","name":"","group":"2b7ac01b.fc984","order":0,"width":0,"height":0,"gtype":"gage","title":"Temperature","label":"ºC","format":"{{value}}","min":0,"max":"40","colors":["#00b500","#e6e600","#ca3838"],"seg1":"","seg2":"","x":650,"y":240,"wires":[]},{"id":"4c53cb0f.3e6084","type":"ui_chart","z":"b01416d3.f69f38","name":"","group":"2b7ac01b.fc984","order":1,"width":0,"height":0,"label":"Temperature","chartType":"line","legend":"false","xformat":"HH:mm:ss","interpolate":"linear","nodata":"","dot":false,"ymin":"","ymax":"","removeOlder":1,"removeOlderPoints":"","removeOlderUnit":"3600","cutout":0,"useOneColor":false,"colors":["#1f77b4","#aec7e8","#ff7f0e","#2ca02c","#98df8a","#d62728","#ff9896","#9467bd","#c5b0d5"],"useOldStyle":false,"outputs":1,"x":650,"y":320,"wires":[[]]},{"id":"8db3fac0.99dd48","type":"mqtt-broker","z":"","name":"","broker":"localhost","port":"1883","clientid":"","usetls":false,"compatmode":false,"keepalive":"60","cleansession":true,"birthTopic":"","birthQos":"0","birthPayload":"","closeTopic":"","closeQos":"0","closePayload":"","willTopic":"","willQos":"0","willPayload":""},{"id":"2b7ac01b.fc984","type":"ui_group","z":"","name":"DS18B20 Temperature Sensor","tab":"99ab8dc5.f435c","disp":true,"width":"6","collapse":false},{"id":"99ab8dc5.f435c","type":"ui_tab","z":"","name":"Home","icon":"dashboard","disabled":false,"hidden":false}]
Demonstration
Go to your Raspberry Pi IP address followed by :1880/ui.

You should get access to the current sensor readings on the Dashboard (gauge and chart).
That’s it! You have your ESP32 board publishing sensor readings to Node-RED via MQTT.
Wrapping Up
MQTT is a great communication protocol to exchange small amounts of data between devices. In this tutorial you’ve learned how to publish DS18B20 temperature readings with the ESP32 on an MQTT topic. Then, you can use any device or home automation platform to subscribe to that topic and receive the readings.
Instead of a DS18B20 temperature sensor, you can use any other sensor and you can also publish on multiple topics at the same time.
We hope you’ve found this tutorial useful. If you want to learn more about the ESP32, take a look at our resources:
Thanks for reading.
36 thoughts on “ESP32 MQTT – Publish DS18B20 Temperature Readings (Arduino IDE)”
Thanks for great tutorial and mqtt knowledge too.
Your RNT resources are very useful for me.
I am thinking how I can do this with the domoticz.
I used sonoff-tasmota for my applications.
Hi.
At the moment, we don’t have any tutorials about that and I’m not familiar with domoticz.
However, if you search for “domoticz MQTT subscribe” you should be able to find out.
Thanks for following our work.
Regards,
Sara
This idea can be made really useful when coupled with a smartphone app. I made a ‘sous vide’ controller in roughly the same way (PID code working on an ESP8266 with the MQTT broker hosted (for convenience) on my Linux server) by installing MQTT Dash on my Android phone. It can both monitor and change the values used by the PID temperature controller. There are other apps that would likely work as well.
excellent tutorial
thanks and keep on the good work
rgds
Carlos Frondizi
My mosquitto broker requires username and password. Any change you indicate where to put this in the code
Hi.
In the code there’s a line that allows you to set the username and password.
mqttClient.setCredentials(“REPlACE_WITH_YOUR_USER”, “REPLACE_WITH_YOUR_PASSWORD”);
Regards,
Sara
Hi, nice tutorial,
I didn’t have a ds18b20, so altered for a bme280. The serial output looks like the MQTT doesn’t really connect and I get no packet acks back. I only changed the mechanism for the temperature readings, not the MQTT connects. packet id is 0 not 1. Mosquitto supposedly runs at boot time.
Node red on my PI looks dead. Also tried to set credentials.
Google app MQTTLens gives a quick and dirty way of monitoring the Mosquitto broker if that is any help.
Red faced, works better when you don’t mistype the brokers IP.
Hi.
Meanwhile, we’ve published a similar tutorial for the BME280: 
Regards,
Sara
Congratulations – this is an excellent tutorial, I think the best I have seen so far. Using this as a basis you can create an unlimited number of ESP32 MQTT applications.
If you could add TLS using a self signed certificate then it could be used for even more applications.
Very well done – Keep up the good work!
Nice project, thank you!
Something does no work at my end
My situation
Local network (IPs 192.168.0.1….255)
RPi MQTT broker 192.168.0.28(:1880)
I did copy the sketch, adjusted the SSID and Passwd data
After successfully compiling the sketch I see among other text in the serial monitor:
confirmation of wifi connection,
connecting to MQTT directly followed by:
Publishing on topic esp32/etc at QoS 1, packetId 0 Message: 23.88 /nDisconnected from MQTT.
The code:
void onMqttConnect(bool sessionPresent) {
}
Serial.println(“Connected to MQTT.”);
Serial.print(“Session present: “);
Serial.println(sessionPresent);
Has not been executed. (NO confirmation of connection)
In the MQTT dashboard the temperature gauge remains 0
Can you give me a direction where to look for a solution?
Thank you for an answer
Hi.
Can you double-check the broker IP address? Also, make sure that the Raspberry Pi is currently running.
It is very difficult to find out what might be wrong without further information.
Regards,
Sara
This is great. Would like to see tutorial/example of subscribing (ei: to a cmd) and doing something (ei: light led or relay)
Joe
Ok, I give up. What is the syntax to get data from a subscription with this library?
Hi.
Example to subscribe to topics:
void onMqttConnect(bool sessionPresent) {
}
Serial.println("Connected to MQTT.");
Serial.print("Session present: ");
Serial.println(sessionPresent);
uint16_t packetIdSub = mqttClient.subscribe("esp32/temperature", 0);
Serial.print("Subscribing at QoS 0, packetId: ");
Serial.println(packetIdSub);
Example to receive message on a subscribed topic:];
if (strcmp(topic, "esp32/temperature") == 0) {
lcd.clear();
lcd.setCursor(1, 0);
lcd.write(0);
lcd.print(" Temperature");
lcd.setCursor(0, 1);
lcd.print(messageTemp);
I hope this helps.
Regards,
Sara
Thank you! Will try soon.
Joe
Hi,
Following everything and failing a lot of times I got the next thing working:
Node Red can read 3x DS18B20 Temp Sensors and one logic input from an ESP-8266 on the network.
However I also need a Push Button in Node red to give a logic pulse to an output pin of the ESP-8266. So I can’t figure out the Subscribe part on the side of ESP.
Even with your Subscribe Receive examples above I can’t figure out or modify a code that works for my application. Any useful tip?
Thanks,
Carlo
Hi Joseph.
We’re planning to write some tutorials about subscribing.
Meanwhile, you can take a look at this project that contains an example of subscribing (however, it doesn’t use the same library).

Regards,
Sara
I have a simple question – where do I find the AsyncMqttClient library? Looked in github but all I saw was to source code to build it. Don’t feel like compiling the source if I can avoid it.
Hi.
You just need to follow the instructions on the tutorial. See the “MQTT Libraries” heading. Everything is explained there. You just need to download the library and then, include it in the libraries folder.
Regards,
Sara
Hi,
I would like to control my device, e.g. ESP32/ESP8266 from any network or anywhere in the world e.g. by installing a webpage on the client side. I still don’t see any tutorial or I may have over seen it.
I am not sure if it is part of a tutorial in one of the books. Please advise.
thank you.
Hi.
Take a look at the following tutorial:

Or this:

Regards,
Sara
Hello
how can i add freertos librery for arduino ide
( #include “freertos/FreeRTOS.h”
#include “freertos/timers.h” )
Hello
how can i add freertos librery for arduino ide
( #include “freertos/FreeRTOS.h”
#include “freertos/timers.h” )
d
Sara,
Thanks for the tutorial. There are several others you have written that are also very useful. Nice work.
If you are still following up on this older tutorial…
I am trying to receive and send several messages from each of the esp32s in my network of esp32s and a pi zero-w broker. With the asyncMQTT library, I am unclear about a few details.
1) Are the “mqttReconnectTimer” and “wifiReconnectTimer” only used if a disconnection occurs, or are they more important that I should adjust them if I am trying to have fast messaging (preferably within a couple hundred milliseconds or less for around 6 topics)?
2) Does there need to be any time delay between publish events in my loop?
3) When receiving and parsing the various topics and messages, can I use the “strcmp” to determine which topic is coming in and process, or do I need to use “strstr”? I am not yet clear if they library is already breaking the messages into single messages or if I need to parse out the string for the relevant topic and work with the pointers like what I think may be done with pubsubclient library (just started with this so I may be very wrong with my assumption).
I am asking since I am having some sort of assumed timing or overlapping data issue on the receiving end. I have to really slow down the publish rate to several seconds to avoid having the receiving being confused with the other topics. I understand MQTT to be very fast so I could have maybe 100ms delay between publish sequences, but that makes my receiver mash everything together. I read a couple posts that suggest I may be having multi core issues with the esp32.
Any suggestions would be appreciated. Thanks again.
OK, I am still interested in questions 1,2,&3 for clarification, but I did find the source of my seemingly overlapping data issue.
I was using “atoi(payload)” directly to the payload to get the int value I needed. That is giving bad results. It does not seem to catch the end of the char array. I am sure I am not using atoi correctly, but I do not understand how to here. My solution was to use the payload to string as written in your original example then use “messageTemp.toInt()” to get the int value I was trying to read. This is a bit of extra work for the processor, but it is allowing me to have 10ms publish increments for integer messages without any delay between publishes in my loop. The results for Qos2 messages seems solid.
If you get around to looking into my initial questions, I would very much appreciate it.
Happy New Year!
I try to get QoS =2 working on an ESP32 with this library.
I can see the data coming in with mosquitto_sub, no problem.
But I cannot see the data in Telegraf, the debugger indicates it wants a ClientID.
How can I set a ClientID in my ESP32 code?
Thank you
Hi.
What project are you following?
Regards,
Sara
Hi Sara,
I am monitoring the weight and temperature of my beehives, so my interest is in making an end node that is in deep sleep most of the time and every 15 minutes or so publishes a few bytes to a Mosquitto broker.
If I do this over WiFi at QoS=0, I have to wait about 1s after publishing to get 99% of the data to the broker. At QoS=1 the node waits for confirmation that the data has reached the broker, and then goes to deep sleep. This takes on average 0.5s, which is clearly better.
What puzzles me is that time from deep sleep to getting an IP address is pretty constant near 175ms, but that the MQTT broker needs anything between 100ms and sometimes a few seconds to complete on a Raspberry Pi that has ‘nothing else to do’.
So I am following your blogs on these subjects. Just to learn and have fun because my current solution at QoS=1 is fit for purpose.
Regards, Rob
Hi all,
The AsyncMqttClient.h library needs the dependencies AsyncTCP for ESP32 and ESPAsyncTCP for ESP8266 but when I try to compile the arduino project it tries to use both.
Everything I could read is about solving this problem in PlatformIO instead of Arduino IDE. How can I avoid this?
Thanks.
Hi.
What is the exact error that you’re getting?
Regards,
Sara
Hello Rui. This is a great tutorial. Thank you.
How could a variable be coded into the mqtt line to change the topic based on the sensor number/ device number? From your code:
// Publish an MQTT message on topic esp32/ds18b20/temperature
uint16_t packetIdPub1 = mqttClient.publish(MQTT_PUB_TEMP, 1, true, String(temp).c_str());
For example, using 2 sensors, MQTT_PUB_TEMP would send “Sensor 0” and the temperature, for 1 sensor; and send “Sensor 1” and the temperature for the other.
Possible?
Best regards
Hi guys, I remember seeing in one of your tutorials about adding network credentials for more than one network, but I can’t find it after searching your site. I’d like to set up my esp device for one network in location 1, then when I move it to another location 2, I can have the sssid and pw included in the code to automatically connect to the network available. Sorry if this isn’t the best place to post this but if not let me know.
Thanks
Terry
Hi, i have a question, when i wanna connect to raspberry pi throught putty, it pop up a message that they cant find host, what can be the problem?
Hi.
Make sure your raspberry pi is on the same network.
Make sure you’re using the right raspberry pi hostname.
If you didn’t change it, it should be the default name: raspberrypi
Regards,
Sara