Problem connecting to Thingspeak with 3G module

Mbed OS
1

Hello everyone, I am trying to make a connection to the thingspeak server, but I don’t know why it could not get the data to the server correctly.
I use two functions, one to configure the modem and another to send, basically when I call the send function, I give it a temperature value in float format, the problem I think is in this part:

    sprintf (http_cmd, "GET https://api.thingspeak.com/update?api_key=%s&field1=%f",Update_Key,value1);
       modem.printf (http_cmd);
       modem.putc (26); // special "CTRL-Z" character

The code that manipulates the module is:

  void ModemInit()
    {
      wait(4);
      uart_debug.printf("Configuring MODEM Telit UL865-NAD");
      modem.printf("AT\r\n");   
      wait(2);
      modem.printf("AT+CGDCONT=1,\"IP\",\"web.tmovil.cl\"\r\n"); 
      wait(3);
      modem.printf("AT#SGACT=1,1\r\n");   
      wait(3);
      modem.printf("AT&K0\r\n");   
      wait(3);
      //modem.printf("AT#SD=1,0,80,\"api.thingspeak.com\",0,0,1\r\n"); 
      //wait(3);

    }

    void server_send(float value1)
    {
      wait(3);
      char* Update_Key = "HOA9X7ZGZ0HLJG9N";
      char http_cmd[300];
      uart_debug.printf("Sending Data to Server ....\r\n");
      uart_debug.printf("AT#SD=1,0,80,\"api.thingspeak.com\",0,0,1\r\n");
      modem.printf("AT#SD=1,0,80,\"api.thingspeak.com\",0,0,1\r\n"); //Open remote connection trough socket.
      wait(3);
      uart_debug.printf("AT#SSEND=1\r\n");
      modem.printf("AT#SSEND=1\r\n"); //SEnd Data
      wait(0.7);
      sprintf(http_cmd,"GET https://api.thingspeak.com/update?api_key=%s&field1=%f",Update_Key,value1);
      modem.printf(http_cmd);
      modem.putc(26); // special "CTRL-Z" character
      wait(0.5);
      uart_debug.printf("AT#SH=1\r\n");
      modem.printf("AT#SH=1\r\n"); //End Connection
      wait(0.5);
    }

Board : STM32F103 aka Bluepill
Module : Telit UL865-NAD

Regards
Francisco

2

Hello,

did you check the response of your AT commands? I think that can help.

BR, Jan

3

Dear JohnnyK, the response to the command is OK, the truth is I don’t know what it could be, I don’t know if I’m creating the string wrong with sprintf, maybe that’s the problem.

Regards
Francisco

4

Hello,

so that OK response tell you the data was send. Now you need read response from the server that will tell you what is wrong, I think.

I found this (section Examples> Write Data with GET, you can verified it from browser) and this maybe it will be useful.

BR, Jan

5

I made this Arduino Code and works perfect :

#include <SoftwareSerial.h>
SoftwareSerial GPRSBee(3,2); // RX, TX

float temp; 
int salida=0;
char dato;


#define SENSOR_TEMP1 "Tem"

void setup() {
  
  Serial.begin(9600); 
  GPRSBee.begin(9600);
  delay(1000);
  
    while(salida==0)
    {
    configuracionGPRSBee();  
    delay(1000);
    }
  serial();
}

void loop() {

  temp= 24.5;
  String Tem = String(temp);
  SendtempGPRSBee(SENSOR_TEMP1, Tem); 
  delay(20000);
   
  }

int serial() 
{
  while(Serial.available() != 0)
  {
    dato = Serial.read();
    GPRSBee.print(dato);
  }
  while(GPRSBee.available() != 0)
  {
    dato = GPRSBee.read();
    Serial.print(dato);
  }
 }

int configuracionGPRSBee()
{

  serial();
  GPRSBee.println("AT");   
  serial();
  delay(3000);
  GPRSBee.println("AT+CGDCONT=1,\"IP\",\"web.tmovil.cl\""); 
  serial();
  delay(3000);
  GPRSBee.println("AT#SGACT=1,1");   
  serial();
  delay(3000);
  GPRSBee.println("AT&K0");   
  serial();
  delay(3000);
  GPRSBee.println("AT#SD=1,0,80,\"api.thingspeak.com\",0,0,1"); 
   serial();
  delay(3000);
  salida=1;
}

int SendtempGPRSBee(String sensor_name, String valor)
{
  GPRSBee.println("AT#SD=1,0,80,\"api.thingspeak.com\",0,0,1"); 
  delay(3000);
  serial();
  delay(1000);
  GPRSBee.println("AT#SSEND=1"); 
  serial();
  delay(700);
  GPRSBee.println("GET https://api.thingspeak.com/update?api_key=HOA9X7ZGZ0HLJG9N&field1="+valor); //pagina web a la que enviamos los datos WEXO4RBDQ7AOHBW2 api KEY
  serial();
  delay(2000);
  GPRSBee.println((char)26); //Caracter para finalizar el mensaje
  delay(500);
  serial();
  GPRSBee.println("AT#SH=1"); 
  delay(500);
  serial();
}

So, my problem is in the part of MBED where I send the data, in arduino it is done as follows:
GPRSBee.println (“GET https://api.thingspeak.com/update?api_key=HOA9X7ZGZ0HLJG9N&field1=”+value);
In the case of arduino, the float value is converted to string.
In the case of mbed, it is done like this:

modem.printf (“AT # SSEND = 1 \ r \ n”); // It works well
wait (0.7);
sprintf (http_cmd, “GET https://api.thingspeak.com/update?api_key=%s&field1=%f”,Update_Key,value1); // Here may be the problem.
modem.printf (http_cmd); // Here may be the problem.
modem.putc (26); // It works fine apparently since the send command is terminated
wait (0.5);
uart_debug.printf (“AT # SH = 1 \ r \ n”);
modem.printf (“AT # SH = 1 \ r \ n”); //It works well
wait (0.5);

Regards
Francisco

6

Ok
I am not familiar with arduino but println method probably include also \r\n at the end of line automatically.
Yes, it is it - Serial.println() - Arduino Reference

You can try to change this

      sprintf(http_cmd,"GET https://api.thingspeak.com/update?api_key=%s&field1=%f",Update_Key,value1);
      modem.printf(http_cmd);

to this

 modem.printf("GET https://api.thingspeak.com/update?api_key=%s&field1=%f\r\n",Update_Key,value1);

And if you want to convert it to string before you can try function to_string (float val); of STD.

 modem.printf("GET https://api.thingspeak.com/update?api_key=%s&field1=%s\r\n",Update_Key, to_string(value1).c_str());

BR, Jan

7

Succes!

modem.printf("GET https://api.thingspeak.com/update?api_key=HOA9X7ZGZ0HLJG9N&field1=%f\r\n",value1);

Thanks so much!!!

Regards
Francisco

1 Like
8

That is great :slight_smile:
Good luck with your project. :+1:

BR, Jan

1 Like