File content as of revision 3:8a57b17395b2:

#include "mbed.h"
#include "ESP8266.h"

Serial pc(USBTX,USBRX);

//POT sensor
AnalogIn pot(PTB0);
AnalogIn lit(PTB1);

//wifi UART port and baud rate
ESP8266 wifi(PTE0, PTE1, 115200);

//buffers for wifi library
char resp[1000];
char http_cmd[300], comm[300];

int timeout = 8000; //timeout for wifi commands

//SSID and password for connection
#define SSID "Karkhana"
#define PASS "Karkhana2018"

//Remote IP
#define IP "184.106.153.149" //  52.202.122.57
//global variable
float potvalue = 0;
float litvalue = 0;

//Update key for thingspeak
char* Update_Key = "OV89R9NLAIJ9NGJ5";
//Wifi init function
void wifi_initialize(void)
{

    pc.printf("******** Resetting wifi module ********\r\n");
    wifi.Reset();

    //wait for 5 seconds for response, else display no response receiveed
    if (wifi.RcvReply(resp, 5000))
        pc.printf("%s",resp);
    else
        pc.printf("No response");


    pc.printf("******** Setting Station mode of wifi with AP ********\r\n");
    wifi.SetMode(1);    // set transparent  mode
    if (wifi.RcvReply(resp, timeout))    //receive a response from ESP
        pc.printf("%s",resp);    //Print the response onscreen
    else
        pc.printf("No response while setting mode. \r\n");


    pc.printf("******** Joining network with SSID and PASS ********\r\n");
    wifi.Join(SSID, PASS);
    if (wifi.RcvReply(resp, timeout))
        pc.printf("%s",resp);
    else
        pc.printf("No response while connecting to network \r\n");


    pc.printf("******** Getting IP and MAC of module ********\r\n");
    wifi.GetIP(resp);
    if (wifi.RcvReply(resp, timeout))
        pc.printf("%s",resp);
    else
        pc.printf("No response while getting IP \r\n");


    pc.printf("******** Setting WIFI UART passthrough ********\r\n");
    wifi.setTransparent();
    if (wifi.RcvReply(resp, timeout))
        pc.printf("%s",resp);
    else
        pc.printf("No response while setting wifi passthrough. \r\n");
    wait(1);


    pc.printf("******** Setting single connection mode ********\r\n");
    wifi.SetSingle();
    wifi.RcvReply(resp, timeout);
    if (wifi.RcvReply(resp, timeout))
        pc.printf("%s",resp);
    else
        pc.printf("No response while setting single connection \r\n");
    wait(1);
}


void wifi_send(void)
{
    pc.printf("******** Starting TCP connection on IP and port ********\r\n");
    wifi.startTCPConn(IP,80);    //cipstart
    wifi.RcvReply(resp, timeout);
    if (wifi.RcvReply(resp, timeout))
        pc.printf("%s",resp);
    else
        pc.printf("No response while starting TCP connection \r\n");
    wait(1);

    //create link
    sprintf(http_cmd,"/update?api_key=%s&field1=%f&field2=%f",Update_Key,potvalue,litvalue);

    pc.printf(http_cmd);

    pc.printf("******** Sending URL to wifi ********\r\n");
    wifi.sendURL(http_cmd, comm);   //cipsend and get command
    if (wifi.RcvReply(resp, timeout))
        pc.printf("%s",resp);
    else
        pc.printf("No response while sending URL \r\n");
}

int main ()
{
    wifi_initialize();
    while (1) {
        potvalue = 255*pot.read();
        litvalue = lit.read();
        pc.printf("Current potvalue is = %.3f \r\n", potvalue);
        pc.printf("Current light value is = %.3f \r\n", litvalue);
        wifi_send();
        wait(1);
    }
}