Programming the ESP8266<\/h2>\n
For the ESP8266 to interact with the Raspberry Pi web server, you need to install\u00a0PubSubClient library<\/a>. This library provides a client for doing simple publish\/subscribe messaging with a server that supports MQTT (basically allows your ESP8266 to talk with Python web server).<\/p>\n 1)\u00a0<\/strong>Click here to download the PubSubClient library<\/a>. You should have a .zip<\/em> folder in your Downloads folder<\/p>\n 2)<\/strong> Unzip the .zip<\/em> folder and you should get pubsubclient-master <\/strong>folder<\/p>\n 3)<\/strong> Rename your folder from\u00a0 4)<\/strong> Move the pubsubclient<\/strong> folder to your Arduino IDE installation libraries<\/strong> folder<\/p>\n The library comes with a number of example sketches. See File<\/strong> > Examples<\/strong> > PubSubClient<\/strong> within the Arduino IDE software.<\/p>\n The\u00a0DHT sensor library<\/a> provides an easy way of\u00a0using any DHT sensor to read temperature and humidity with your ESP8266 or Arduino boards.<\/p>\n 1)<\/strong> Click here to download the DHT sensor\u00a0library<\/a>. You should have a\u00a0.zip<\/em> folder in your Downloads folder<\/p>\n 2)<\/strong> Unzip the .zip<\/em> folder and you should get DHT-sensor-library-master <\/strong>folder<\/p>\n 3)<\/strong> Rename your folder from\u00a0 4)<\/strong> Move the DHT\u00a0<\/strong>folder to your Arduino IDE installation\u00a0libraries<\/strong> folder<\/p>\n 5)<\/strong>\u00a0Then, re-open your Arduino IDE<\/p>\n<\/div>\n Finally, you can upload the full sketch to your ESP8266 (replace with your SSID, password and RPi IP address):<\/p>\n View raw code<\/a><\/p>\n<\/div>\n To complete this project\u00a0you need\u00a0these next components:<\/p>\n Note:<\/strong>\u00a0other DHT sensor types will also work with a small\u00a0change in the code.<\/p>\n You can use the preceding links or go directly to MakerAdvisor.com\/tools<\/a> to find all the parts for your projects at the best price!<\/p> Here\u2019s the schematics:<\/p>\n Important:<\/strong><\/span>\u00a0the\u00a0DHT sensor requires 5V to operate properly, so make sure you use the Vin<\/em> pin from your ESP8266 that outputs 5V.<\/p>\n To launch your Raspberry Pi web server move to the folder that contains the file app.py<\/em>:<\/p>\n Then, run the following command:<\/p>\n Your web server should start immediately on port :8181!<\/p>\n Open your Raspberry Pi address in your browser by entering its IP address, in my case:\u00a0http:\/\/192.168.1.98:8181<\/p>\n Note: you must enter your IP\u00a0address followed by :8181<\/strong><\/p>\n <\/p>\n That’s it for now, I hope you can take these examples and build\u00a0more features that fit your needs.<\/p>\n Like home automation? Learn more about Node-RED, Raspberry Pi, ESP8266 and Arduino\u00a0with\u00a0my course:\u00a0Build a Home Automation System for $100<\/a>.<\/p>\n Do you have any questions?\u00a0<\/strong>Leave a comment down below!<\/strong><\/p>\n Thanks for reading. If you like this post probably you might like my next ones, so please support me by subscribing my blog<\/a>.<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":" In this project you\u2019ll create a standalone web server with a Raspberry Pi that displays temperature and humidity readings with a DHT22 sensor that are stored in an SQLite database. … <\/p>\nInstalling the PubSubClient library<\/h3>\n
pubsubclient-master<\/strong><\/del>\u00a0to\u00a0pubsubclient<\/strong><\/p>\nInstalling the DHT sensor library<\/h3>\n
DHT-sensor-library-master<\/strong><\/del>\u00a0to\u00a0DHT<\/strong><\/p>\nUploading sketch<\/h3>\n
\/*****\n \n All the resources for this project:\n https:\/\/rntlab.com\/\n \n*****\/\n\n\/\/ Loading the ESP8266WiFi library and the PubSubClient library\n#include <ESP8266WiFi.h>\n#include <PubSubClient.h>\n#include "DHT.h"\n\n\/\/ Uncomment one of the lines bellow for whatever DHT sensor type you're using!\n\/\/#define DHTTYPE DHT11 \/\/ DHT 11\n\/\/#define DHTTYPE DHT21 \/\/ DHT 21 (AM2301)\n#define DHTTYPE DHT22 \/\/ DHT 22 (AM2302), AM2321\n\n\/\/ Change the credentials below, so your ESP8266 connects to your router\nconst char* ssid = "YOUR_SSID";\nconst char* password = "YOUR_PASSWORD";\n\n\/\/ Change the variable to your Raspberry Pi IP address, so it connects to your MQTT broker\nconst char* mqtt_server = "YOUR_RPi_IP_Address";\n\n\/\/ Initializes the espClient\nWiFiClient espClient;\nPubSubClient client(espClient);\n\n\/\/ DHT Sensor\nconst int DHTPin = 14;\n\n\/\/ Initialize DHT sensor.\nDHT dht(DHTPin, DHTTYPE);\n\n\/\/ Timers auxiliar variables\nlong now = millis();\nlong lastMeasure = 0;\n\nchar data[80];\n\n\/\/ Don't change the function below. This functions connects your ESP8266 to your router\nvoid setup_wifi() {\n delay(10);\n \/\/ We start by connecting to a WiFi network\n Serial.println();\n Serial.print("Connecting to ");\n Serial.println(ssid);\n WiFi.begin(ssid, password);\n while (WiFi.status() != WL_CONNECTED) {\n delay(500);\n Serial.print(".");\n }\n Serial.println("");\n Serial.print("WiFi connected - ESP IP address: ");\n Serial.println(WiFi.localIP());\n}\n\n\/\/ This functions is executed when some device publishes a message to a topic that your ESP8266 is subscribed to\n\/\/ Change the function below to add logic to your program, so when a device publishes a message to a topic that \n\/\/ your ESP8266 is subscribed you can actually do something\nvoid callback(String topic, byte* message, unsigned int length) {\n Serial.print("Message arrived on topic: ");\n Serial.print(topic);\n Serial.print(". Message: ");\n String messageTemp;\n \n for (int i = 0; i < length; i++) {\n Serial.print((char)message[i]);\n messageTemp += (char)message[i];\n }\n Serial.println();\n}\n\n\/\/ This functions reconnects your ESP8266 to your MQTT broker\n\/\/ Change the function below if you want to subscribe to more topics with your ESP8266 \nvoid reconnect() {\n \/\/ Loop until we're reconnected\n while (!client.connected()) {\n Serial.print("Attempting MQTT connection...");\n \/\/ Attempt to connect\n \/*\n YOU NEED TO CHANGE THIS NEXT LINE, IF YOU'RE HAVING PROBLEMS WITH MQTT MULTIPLE CONNECTIONS\n To change the ESP device ID, you will have to give a unique name to the ESP8266.\n Here's how it looks like now:\n if (client.connect("ESP8266Client")) {\n If you want more devices connected to the MQTT broker, you can do it like this:\n if (client.connect("ESPOffice")) {\n Then, for the other ESP:\n if (client.connect("ESPGarage")) {\n That should solve your MQTT multiple connections problem\n\n THE SECTION IN loop() function should match your device name\n *\/\n if (client.connect("ESP8266Client")) {\n Serial.println("connected"); \n \/\/ Subscribe or resubscribe to a topic\n \/\/ You can subscribe to more topics (to control more LEDs in this example)\n } else {\n Serial.print("failed, rc=");\n Serial.print(client.state());\n Serial.println(" try again in 5 seconds");\n \/\/ Wait 5 seconds before retrying\n delay(5000);\n }\n }\n}\n\n\/\/ The setup function sets your DHT sensor, starts the serial communication at a baud rate of 115200\n\/\/ Sets your mqtt broker and sets the callback function\n\/\/ The callback function is what receives messages and actually controls the LEDs\nvoid setup() {\n dht.begin();\n Serial.begin(115200);\n setup_wifi();\n client.setServer(mqtt_server, 1883);\n client.setCallback(callback);\n}\n\n\/\/ For this project, you don't need to change anything in the loop function. \n\/\/ Basically it ensures that you ESP is connected to your broker\nvoid loop() {\n if (!client.connected()) {\n reconnect();\n }\n if(!client.loop())\n \/*\n YOU NEED TO CHANGE THIS NEXT LINE, IF YOU'RE HAVING PROBLEMS WITH MQTT MULTIPLE CONNECTIONS\n To change the ESP device ID, you will have to give a unique name to the ESP8266.\n Here's how it looks like now:\n client.connect("ESP8266Client");\n If you want more devices connected to the MQTT broker, you can do it like this:\n client.connect("ESPOffice");\n Then, for the other ESP:\n client.connect("ESPGarage");\n That should solve your MQTT multiple connections problem\n\n THE SECTION IN recionnect() function should match your device name\n *\/\n client.connect("ESP8266Client");\n \n now = millis();\n \/\/ Publishes new temperature and humidity every 30 seconds\n if (now - lastMeasure > 10000) {\n lastMeasure = now;\n \/\/ Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)\n float h = dht.readHumidity();\n \/\/ Read temperature as Celsius (the default)\n float t = dht.readTemperature();\n \/\/ Read temperature as Fahrenheit (isFahrenheit = true)\n float f = dht.readTemperature(true);\n\n \/\/ Check if any reads failed and exit early (to try again).\n if (isnan(h) || isnan(t) || isnan(f)) {\n Serial.println("Failed to read from DHT sensor!");\n return;\n }\n\n \/\/ Computes temperature values in Celsius\n float hic = dht.computeHeatIndex(t, h, false);\n static char temperatureTemp[7];\n dtostrf(hic, 6, 2, temperatureTemp);\n \n \/\/ Uncomment to compute temperature values in Fahrenheit \n \/\/ float hif = dht.computeHeatIndex(f, h);\n \/\/ static char temperatureTemp[7];\n \/\/ dtostrf(hic, 6, 2, temperatureTemp);\n \n static char humidityTemp[7];\n dtostrf(h, 6, 2, humidityTemp);\n \n String dhtReadings = "{ \\"temperature\\": \\"" + String(temperatureTemp) + "\\", \\"humidity\\" : \\"" + String(humidityTemp) + "\\"}";\n dhtReadings.toCharArray(data, (dhtReadings.length() + 1));\n \n \/\/ Publishes Temperature and Humidity values\n client.publish("\/esp8266\/dhtreadings", data);\n Serial.println(data);\n Serial.print("Humidity: ");\n Serial.print(h);\n Serial.print(" %\\t Temperature: ");\n Serial.print(t);\n Serial.print(" *C ");\n Serial.print(f);\n Serial.print(" *F\\t Heat index: ");\n Serial.print(hic);\n Serial.println(" *C ");\n \/\/ Serial.print(hif);\n \/\/ Serial.println(" *F");\n }\n}\n<\/code><\/pre>\n\tSchematics<\/h3>\n
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![](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/03\/DHT22_RaspberryPi_ESP8266.jpg?quality=100&strip=all&ssl=1\")
<\/a><\/p>\n<\/p>\nLaunching the Web Server<\/h2>\n
pi@raspberrypi:~\/web-server\/templates $ cd ..<\/strong><\/pre>\n
pi@raspberrypi:~\/web-server $ sudo python app.py<\/strong><\/pre>\n
Demonstration<\/h2>\n
<\/p>\nWrapping up<\/h2>\n