#include <SoftwareSerial.h>

// LED 
int ledPin = 13;
int sensor_pin=A4;  // variable for sensor
int sensor_pin1=A3;  // variable for sensor
int sensor_pin2=A2;  // variable for sensor
float sample=0;
float bat_volt =0;     // for temperature

int sensorValue = 0;        // value read from the pot
int sensorValue1 = 0;
int sensorValue2 = 0;
int outputValue = 0;        // value output to the PWM (analog out)
int outputValue1 = 0;
int outputValue2 = 0;

// replace with your channel's thingspeak API key
String apiKey = "your api here"

// connect 2 to TX of Serial USB
// connect 3 to RX of serial USB
SoftwareSerial ser(2,3); // RX, TX

// this runs once
void setup() {                
  // initialize the digital pin as an output.
  pinMode(ledPin, OUTPUT);    

  // enable debug serial
  Serial.begin(115200); 
  ser.begin(115200);
  // enable software serial
  
  // reset ESP8266
  ser.println("AT+RST");
}


// the loop 
void loop() {
  
  // blink LED on board
  digitalWrite(ledPin, HIGH);   
  delay(200);               
  digitalWrite(ledPin, LOW);

  voltage();
  esp_8266();
}
void voltage()
{
    
sensorValue = analogRead(sensor_pin);
sensorValue1 = analogRead(sensor_pin1);
sensorValue2 = analogRead(sensor_pin2);
  // map it to the range of the analog out:
  outputValue = map(sensorValue, 0, 1023, 0, 255);
  outputValue1 = map(sensorValue1, 0, 1023, 0, 255);
  outputValue2 = map(sensorValue2, 0, 1023, 0, 255);
 
  
}
void esp_8266()
{
 // convert to string
  char buf[32];
  
  Serial.print(outputValue);
  Serial.println(" %");
  // TCP connection
  String cmd = "AT+CIPSTART=\"TCP\",\"";
  cmd += "184.106.153.149"; // api.thingspeak.com
  cmd += "\",80";
  ser.println(cmd);
   
  if(ser.find("Error")){
    Serial.println("AT+CIPSTART error");
    return;
  }
  
  // prepare GET string
  String getStr = "GET /update?api_key=";
  getStr += apiKey;
  getStr +="&field1=";
  getStr += outputValue;
   getStr +="&field2=";
  getStr += outputValue1;
   getStr +="&field3=";
  getStr += outputValue2;
  getStr += "\r\n\r\n";

  // send data length
  cmd = "AT+CIPSEND=";
  cmd += String(getStr.length());
  ser.println(cmd);

  if(ser.find(">")){
    ser.print(getStr);
  }
  else{
    ser.println("AT+CIPCLOSE");
    // alert user
    Serial.println("AT+CIPCLOSE");
  }
    
  // thingspeak needs 15 sec delay between updates
  delay(16000);  
}