Using the ESP8266, you can log sensor data to online servers for monitoring and control purposes. In this recipe, we will be looking at how to do that. We will use an ESP8266 board to post and store sensor data on dweet.io.
To do this tutorial, you will need an ESP8266 board and a USB cable among several other things, which include:
- DHT11 (https://www.sparkfun.com/products/10167)
- Soil moisture sensor (https://www.sparkfun.com/products/13322)
- 220 Ω resistor
- 100 Ω resistor
- 10 kΩ resistor
- Breadboard
- Jumper wires
The hardware setup will resemble the one in the previous recipe.
In addition to setting up the hardware, you will set up the online platform where the sensor data will be posted. Luckily the platform we are using, dweet.io, is simple to use and requires no setup or signup. All you need to do is choose a name for your thing, which in this case is your ESP8266, then you can start publishing data to dweet.io.
Posting data to dweet.io is simple. It is done by calling a URL such as https://dweet.io/dweet/for/my-thing-name?hello=world. You are required to change my-thing-name to the name of your thing, hello to the name of the parameter that you are posting, and world to the value of the parameter that you are posting online.
In our case, we will call our thing garden-monitor-11447, and the names of the parameters we will be posting are humidity, temperature, and moisture. Our URL will look like this: https://dweet.io/dweet/for/garden-monitor-11447?humidity=<humidity value>&temperature=<temperature value>&moisture=<moisture value>.
Once you have successfully generated the URL:
- Connect the ESP8266 board to a Wi-Fi network that has Internet connection and then read the
humidity,temperature, andsoil moisturevalues from the sensors, as done in the previous recipe. - Replace the
<humidity value>,<temperature value>, and<moisture value>in the preceding URL with the readings obtained from the sensors. The URL will be used to send ahttprequest to thedweet.ioserver. - When the ESP8266 successfully sends the
httprequest, the sensor data will be published on thedweet.ioplatform. To view the data, visit this URL from any web browser: https://dweet.io/follow/garden-monitor-11447:// Libraries #include <ESP8266WiFi.h> #include "DHT.h"
ssidandpasswordis set in this section:// Wi-Fi network SSID and password const char* ssid = "your-ssid"; const char* password = "your-password";
- Store the
hostname of the cloud server:// Host const char* host = "dweet.io";
- Define the pin that is connected to the
DHT11signal pin and the type ofDHTsensor that we are using:#define DHTPIN 2 // what digital pin DHT11 is connected to #define DHTTYPE DHT11 // DHT 11 sensor
- Create a
dhtobject:DHT dht(DHTPIN, DHTTYPE);
- Declare a variable that will hold the
moistureReading:int moistureReading = 0; // holds value soil moisture sensor reading
- Initialize the serial interface and the
DHTobject. Configure thessidandpasswordof the Wi-Fi network and connect the ESP8266 to it:void setup() { Serial.begin(115200); // initialize serial interface dht.begin(); // initialize DHT11 sensor delay(10); // We start by connecting to a WiFi network Serial.println(); Serial.println(); Serial.print("Connecting to "); Serial.println(ssid); WiFi.begin(ssid, password); while (WiFi.status() != WL_CONNECTED) { delay(500); Serial.print("."); } Serial.println(""); Serial.println("WiFi connected"); Serial.println("IP address: "); Serial.println(WiFi.localIP()); } - Delay for five seconds, then print the name of the host we are connecting to on the serial monitor:
void loop() { delay(5000); Serial.print("connecting to "); Serial.println(host); - Connect to the
hostserver. Retry if not successful:// Use WiFiClient class to create TCP connections WiFiClient client; const int httpPort = 80; if (!client.connect(host, httpPort)) { Serial.println("connection failed"); return; } - Get readings from the
DHT11sensor andsoil moisturesensor:// Read sensor inputs // get humidity reading float h = dht.readHumidity(); // get temperature reading in Celsius float t = dht.readTemperature(); // Check if any reads failed and exit early (to try again). while (isnan(h) || isnan(t)) { Serial.println("Failed to read from DHT sensor!"); delay(2000); // delay before next measurements //get the measurements once more h = dht.readHumidity(); t = dht.readTemperature(); } //get soil moisture reading moistureReading = analogRead(A0);- Generate a URL for the
GETrequest we will send to the host server. The URL will include the sensor readings:// We now create a URI for the request String url = "/dweet/for/garden-monitor-11447?humidity="; url += String(h); url += "&temperature="; url += String(t); url += "&moisture="; url += String(moistureReading);
- Generate a URL for the
- Send the
GETrequest to the server and check whether the request has been received, or if it has been timed out:// Send request Serial.print("Requesting URL: "); Serial.println(url); client.print(String("GET ") + url + " HTTP/1.1 " + "Host: " + host + " " + "Connection: close "); unsigned long timeout = millis(); while (client.available() == 0) { if (millis() - timeout > 5000) { Serial.println(">>> Client Timeout !"); client.stop(); return; } }- Read incoming data from the
hostserver line by line and display the data on the serial monitor. Close the connection after all the data has been received from the server:// Read all the lines from the answer while(client.available()){ String line = client.readStringUntil(' '); Serial.print(line); } // Close connecting Serial.println(); Serial.println("closing connection"); }
- Read incoming data from the
- Copy the sketch to your Arduino IDE and change the
ssidin the code fromyour-ssidto the name of your Wi-Fi network, and thepasswordfromyour-passwordto the password of your Wi-Fi network. - Upload the sketch to your ESP8266 board. Open the serial monitor so that you can view the incoming data.
The program connects to the Wi-Fi network using the provided password and ssid. It then proceeds to connect to the provided cloud/host server using the client.connect() function. Once the ESP8266 connects successfully, data from the sensors is read and a URL is generated that includes the updated sensor data. The URL is then sent to the host server using the client.print() function.
Once the data has been successfully sent, the sketch waits for a reply from the server. It does this with the client.available() function, which checks whether there is incoming data from the server. If there is data available, the sketch reads it and displays it on the serial monitor. The ESP8266 posts sensor data to dweet.io every five seconds.