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Controller not able to collect response from GSM Modem

sanjyot kadu

Hello all,

I am trying to send Command from 89S52 Controller to SIM900 GSM Modem

when i am sending command as

"AT" in response my Receive buffer is able to receive all bytes and code is working fine.

if request is "AT"Response is "AT 0X0D 0X0A 0X0D 0X0A OK " -> working fine

but if i send command as “AT+IPR=9600”

then expected response should be same "AT 0X0D 0X0A 0X0D 0X0A OK " but my buffer is not able to collect it.

it is receiving "AT " and after this it is receiving junk characters (in second attempt i tried to make buffer memory dynamically allocated but that is making program more dirty)

GSM is responding correctly (i verified it using hyperterminal), my code is not able to receive it correctly.

/*drivers.c*/


extern int buf_count;
char Rec_buf[10] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

void serial_IT(void) interrupt 4
{
 if (RI == 1)
 {
         /* if reception occur */
   RI = 0; /* clear reception flag for next reception */
   Rec_buf[buf_count] = SBUF; /* Read receive data */

         buf_count++;
         if(buf_count == 10)
         {
                buf_count = 0;
   }
 }

}



void Send_cmd(char *cmd)
{
  while(*cmd != '\0')
  {
   Uart_send(*cmd);
         cmd++;
  }

  Uart_send(0x0D);
  Uart_send(0X0A);

}

void Uart_send(char data_snd)
{
        TI = 0;
        SBUF = data_snd;
        while(TI==0);
        TI = 0;
}



/*application.c*/

int Check_rsponse_OK(void)
{
                int ret_val = 0;
          if(Rec_buf[0] == 'A' && Rec_buf[1] == 'T' && Rec_buf[2] == 0x0D && Rec_buf[3] == 0X0A && Rec_buf[4] == 0x0D && Rec_buf[5] == 0x0A &&  Rec_buf[6] == 'O' && Rec_buf[7] == 'K')
                {
                                port_0_0 = 1;
                                port_0_1 = 0;
                          ret_val = 1;
                }
                else
                {
                                port_0_0 = 0;
                                port_0_1 = 1;
                          ret_val = 0;
                }
                return ret_val;
}


/*main.c*/

void main (void)
{

 int ret_val = 0;

 init_app( );

 Send_cmd(Check_cmd);

do
 {
        ret_val = Check_rsponse_OK();
 }while(ret_val != 1);

 Reset_receiver_Buffer();
 while(1);

}

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