Simple ESP32 IoT Sensor Node Tutorial: WiFi Enabled MQTT Sensor Data Node

in this video we're going to create an esp32 based sensor node that together with a BME 680 sensor will measure temperature pressure humidity and air quality and send all this data over Wi-Fi and the mqtt protocol to our Raspberry Pi 4 based iot server we made this server in a previous video and essentially what this does is take our sensor data store it in a database and allow us to see it visually in a grafana dashboard this video is going to focus on the sensor side of this project so if you want to have a look at the server video I'll link that in the cards above and also down in the description so let's get into what we're going to use for this project we're going to use an esp32 Dev board this is just a generic Dev board um which is an AliExpress special probably a clone of a clone of a clone um but any Dev board will do in terms of sensors you can use really whatever sensor you like in this situation and it all depends on what data you want to measure I will be using a BME 680 sensor from Adafruit but you can easily adapt this project for other sensors we're going to need a variety of jump cables to connect the sensor to the esp32 board as well as some kind of power supply to power the sensor mode as I'm going to have this sensor in my office I'm going to plug it in via USB directly to the Raspberry Pi server which is on 24 7. finally we're going to need the iot server that we made in our previous video and we're going to program everything in the Arduino IDE so how will the sensor node work as I previously mentioned this sensor node will transmit sensor data over Wi-Fi via the mqtt protocol mqtt is a network protocol where essentially a client pushes data to a broker the client in this case is the esp32 and the broker is an application called mosquito running on our Raspberry Pi server the sensor data will be sent as a Json string this flowchart shows how the how the software will work from a more detailed perspective I've kind of had to make this somewhat horizontal flowchart to make it fit into a 16x9 frame but hopefully it's clear enough for you guys to see essentially our code that will run on the esp32 will start by opening a serial connection to print some debug messages then we will check if we have wired up the sensor correctly and once we've connected to the sensor we will attempt to connect to a Wi-Fi network once we've connected to our Wi-Fi network we'll then try and attempt to our mqtt server and after all this setup is complete we enter a main Loop which reads the sensor data packages it into a Json message and sends it to the mqtt server then this process is repeated as an interval of your choosing the Json message is essentially the value of the sensor reading say temperature with a key which is representative of what the sensor is reading for example a key of T would indicate that the sensor reading is temperature this is then decoded by the server and then stored properly in our database the Arduino libraries that we're going to use are the BME 680 and sensor libraries the pub sub client for mqtt communication Arduino Json to create our Json message wire to enable I squared C communication and Wi-Fi to enable our network connectivity as I mentioned we're using I squared C to connect the BME 680 sensor to the esp32 dev board this requires four jumper cables power ground and then clock and data lines in order to implement our program in the Arduino IDE the first thing we need to do is install the esp32 boards package from espressive if you haven't done that already and this is done by adding the following URL to the additional boards manager in file then preferences this is the first time you've done this it might prompt you to install the board and that will appear in the bottom right hand side and you just hit install in terms of the libraries we listed to install them you need to open the library manager by clicking on this icon and then searching for the libraries you don't have installed and install them right so now let's get programming I will explain everything as I go through it but if you want to skip this then the full source code is available on our website link down in the description and if you'd like to challenge yourself perhaps go back to the slide where I showed you the programming flowchart and see if you could start off there and perhaps at the end when you finish that compare with what are what we programmed we are starting with a fresh Arduino sketch and first things first we need to include all of the libraries we previously listed after this we create another function called reconnect for a total of three that is setup Loop and reconnect then we create a BME object which initializes the bme680 sensor over I squared C and we do that using the Adafruit underscore bme680 Constructor then we create three Char arrays or character arrays to store your Wi-Fi network SSID and password as well as the IP address of the mqtt server obviously I've blanked out my network details here but just substitute yours in they're in plain text and make sure to include the quotation marks either side then we create a Wi-Fi client simply called ESP client and then we tell the pub sub client which client we used there's a lot of clients there but just follow this code here now let's start with our setup function the code in the setup function runs once when the program is started we will start with 100 millisecond delay to make sure that everything is started up and running properly then start the serial connection with a baud rate of 115 200 and wait for the serial connection to be opened before continuing then we test to see if we can connect the BME sensor by using an if statement and in the the condition of that if statement we use the BME dot begin function and we check whether it returns a one or a zero if the BME sensor is not detected then we enter an infinite while loop and that will just prompt us to you know unplug the board check our wiring try again then we need to configure the BME sensor and I'm using the default values here from Adafruit so I'm just going to copy paste them over I advise you to do the same but if you really want to get into the wheeze of things then have a look at the data sheet of the bme680 sensor and maybe have a play around with what these values do then we attempt to connect to our Wi-Fi network I'm going to print some debug messages before using the wi-fi.begin function with the SSID and password we previously set as arguments to check that we are connected we're going to use a while loop which checks the Wi-Fi status against the WL underscore connected condition in this while loop we print out a sort of loading bar of dots every half a second whilst we wait for the Wi-Fi network to connect as this can sometimes take a couple of seconds once connected we print out an alert over serial so we know things are working as anticipated finally in the setup function we set up the mqtt server details with client.set server and then the server IP address and the port of the mqtt server which is 1883 as a as a default the first thing we're going to do in our main Loop is check if we are connected to the mqtt server the first time the program enters this Loop we won't be connected and so this function will run let's write this function now in this function we create a while loop which Loops until we are connected I'll print a debug message so that we can check what's going on we then allocate a client ID to this device in the form of a string and a random number appended to the end of the string then we attempt to connect to the mqtt server using the client.connect function with the client ID as an argument this function is used in the condition of the if statement if the connection fails then we print out the error code for debugging with that function complete we can now go back to our main Loop firstly we create a static Json document which will contain the sensor data we read from the sensor we can also create a character array and call it something like output which will store the Json message we want to send to the mqtt server then we create a variable to store the current time and this will be used as a kind of timer we then create an if statement which will effectively Implement a 10 second delay between running the code in this if statement note that here I forget to declare the last message variable but that's an unsigned long and I fix it once I try and compile it and sort of face palm in a couple of minutes then we read the temperature pressure humidity and air quality data into temporary variables using the bme.read functions then we need to add these variables into the Json document each value has a key Associated to it to indicate what value is being stored after this we use the serialized Json function to turn this document into a string that can be sent across the network using the client.publish function which takes the argument of the topic to push the data to in this case home sensors and the Char array of the Json message with all this written we can compile the code and upload it to the board obviously you can see this has warned me that I've missed the Declaration of a variable but with that fixed I can upload the code now and once uploaded we should be able to see that the sensor data being sent across the xeron monitor is the sort of um what we want to be sent across the network and this should be updated every 10 seconds if we open up grafana we should see all this data being populated so this is quite a straightforward project so please feel free to adapt this to your needs do let us know how you want to use this project down in the comments we love to see how you use the things you learn in our videos if this video has helped you out then please consider liking and subscribing thank you very much for watching and as always have a nice day

Channel: Learn Embedded Systems

Views: 42,014

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Id: x5A5S0hoyJ0

Length: 10min 58sec (658 seconds)

Published: Mon Nov 28 2022