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1/*
2
3Problem Statement: Upload temperature data(LM35) to your channel on ThingSpeak
4Developed by: Rahul Shrivastava
5****************************************************
6Hardware Connections
7
8LM35    NODEMCU
91 (Vcc)   3v3 (3.3 Volts)
102 (OUT)   A0 (Analog Input)
113 (GND)   GND   
12****************************************************
13*/
14
15#include <ESP8266WiFiMulti.h>// Wifi
16#include <ESP8266HTTPClient.h>// HTTP
17
18ESP8266WiFiMulti WiFiMulti;
19
20String api_key = "V73YPTI4XFBKRT3C";// write API key
21int field_no = 1;// temperature
22
23void setup() {
24    Serial.begin(115200);
25    Serial.flush();
26    pinMode(D0, OUTPUT); 
27    wificonnect();         
28}
29
30void loop() {
31        float tempC = sensorRead(A0);
32        GETsend(tempC);
33}
34
35void wificonnect()
36  {
37    WiFiMulti.addAP("InternetHere1", "oist@1986");// AP --> Access Point, SSID
38    Serial.println("Conneting");
39    while(WiFiMulti.run()!=WL_CONNECTED)
40    {
41      Serial.print(".");
42      digitalWrite(D0, LOW);
43      delay(100);
44      digitalWrite(D0, HIGH);
45      delay(100);
46    }
47     Serial.print("Connected to HOTSPOT..\n");// This line will execute if your device is connected to Access Pass
48  }
49
50void GETsend(float data)
51{
52        HTTPClient http; //http is the object of class HTTPClient this class defines the method to create and send HTTP requests            
53        //https://api.thingspeak.com/update?api_key=V73YPTI4XFBKRT3C&field1=0
54        String url =  "http://api.thingspeak.com/update?api_key=";
55               url += api_key;
56               url += "&field";
57               url += field_no;
58               url += "=";// Creating HTTP Query/GET Method
59               url += data;// passing the parameter to string, this value will reach cloud at field1
60        http.begin(url);// initiate HTTP Request to establish connection  
61
62        Serial.print("HTTP REQUEST SENT, Waiting for response\n");
63        
64        // start connection and send HTTP header
65        int httpCode = http.GET();// get method, returns a http code, -ve if access denied
66        // httpCode will be negative on error      
67        if(httpCode > 0) {
68            // HTTP header has been send and Server response header has been handled
69            Serial.println("Sensor data uploaded sucessfully");                          
70         }
71        else
72         {
73            Serial.println("Failed to connect to server");
74         }         
75 http.end();   
76    delay(16000);// 16sec  
77}
78
79float sensorRead (int sensorPin)
80{
81  float x = analogRead(sensorPin);
82  float voltage = x * 3.3 / 1023;
83  float voltage_mv = voltage*1000;
84  float temp = voltage_mv/10;   
85  return temp;
86}