Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
ESP8266 + MQTT + DHT11 Humidity and Temperature Sensor
/* ESP8266 + MQTT Humidity and Temperature Node
* Can also receive commands; adjust messageReceived() function
* See MakeUseOf.com for full build guide and instructions
* Author: James Bruce, 2015
*/
#include <MQTTClient.h>
#include <ESP8266WiFi.h>
#include <DHT.h>
const char* ssid = "YOUR_SSID";
const char* password = "YOUR_PASSWORD!";
char* subscribeTopic = "openhab/parentsbedroom/incoming"; // subscribe to this topic; anything sent here will be passed into the messageReceived function
char* tempTopic = "openhab/parentsbedroom/temperature"; //topic to publish temperatures readings to
char* humidityTopic = "openhab/parentsbedroom/humidity"; // publish humidity readings
const char* server = "192.168.1.99"; // server or URL of MQTT broker
String clientName = "parentsbedroom-"; // just a name used to talk to MQTT broker
long interval = 60000; //(ms) - 60 seconds between reports
unsigned long resetPeriod = 86400000; // 1 day - this is the period after which we restart the CPU, to deal with odd memory leak errors
#define DHTTYPE DHT11 // DHT11 or DHT22
#define DHTPIN 2
unsigned long prevTime;
DHT dht(DHTPIN, DHTTYPE,11);
float h, t;
WiFiClient wifiClient;
MQTTClient client;
String macToStr(const uint8_t* mac)
{
String result;
for (int i = 0; i < 6; ++i) {
result += String(mac[i], 16);
if (i < 5)
result += ':';
}
return result;
}
void setup() {
Serial.begin(115200);
dht.begin();
client.begin(server,wifiClient);
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());
// Generate client name based on MAC address and last 8 bits of microsecond counter
uint8_t mac[6];
WiFi.macAddress(mac);
clientName += macToStr(mac);
clientName += "-";
clientName += String(micros() & 0xff, 16);
Serial.print("Connecting to ");
Serial.print(server);
Serial.print(" as ");
Serial.println(clientName);
if (client.connect((char*) clientName.c_str())) {
Serial.println("Connected to MQTT broker");
Serial.print("Subscribed to: ");
Serial.println(subscribeTopic);
client.subscribe(subscribeTopic);
}
else {
Serial.println("MQTT connect failed");
Serial.println("Will reset and try again...");
abort();
}
prevTime = 0;
}
void loop() {
static int counter = 0;
if(prevTime + interval < millis() || prevTime == 0){
prevTime = millis();
Serial.println("checking again");
Serial.println(prevTime);
h = dht.readHumidity();
t = dht.readTemperature();
h = h*1.23;
t = t*1.1;
// Check if any reads failed and exit early (to try again).
if (isnan(h) || isnan(t)) {
Serial.println("Failed to read from DHT sensor!");
}
else if(!client.connected()){
Serial.println("Connection to broker lost; retrying");
}
else{
char* tPayload = f2s(t,0);
char* hPayload = f2s(h,0);
Serial.println(t);
Serial.println(h);
Serial.println(tPayload);
Serial.println(hPayload);
client.publish(tempTopic, tPayload);
client.publish(humidityTopic, hPayload);
Serial.println("published environmental data");
}
}
client.loop();
// reset after a day to avoid memory leaks
if(millis()>resetPeriod){
ESP.restart();
}
}
/* float to string
* f is the float to turn into a string
* p is the precision (number of decimals)
* return a string representation of the float.
*/
char *f2s(float f, int p){
char * pBuff; // use to remember which part of the buffer to use for dtostrf
const int iSize = 10; // number of buffers, one for each float before wrapping around
static char sBuff[iSize][20]; // space for 20 characters including NULL terminator for each float
static int iCount = 0; // keep a tab of next place in sBuff to use
pBuff = sBuff[iCount]; // use this buffer
if(iCount >= iSize -1){ // check for wrap
iCount = 0; // if wrapping start again and reset
}
else{
iCount++; // advance the counter
}
return dtostrf(f, 0, p, pBuff); // call the library function
}
void messageReceived(String topic, String payload, char * bytes, unsigned int length) {
Serial.print("incoming: ");
Serial.print(topic);
Serial.print(" - ");
Serial.print(payload);
Serial.println();
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.