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I am trying to communicate between AT89S52 microcontroller and NEOWAY M590E gsm module.

Gabzz abdul

I am trying to communicate between AT89S52 microcontroller and NEOWAY M590E gsm module.I use HTerm to in communicating with the MCU it works perfectly. Whenever i connect the modem to the MCU it does nothing. For each command it sends , i allow it to turn on a the led of different ports. Unfortunately, none of the leds came on. I wonder why that is. KIndly help me out.

#include <reg51.h>

void confirmPBready(void);
void BYTEwrite( unsigned char VAL, unsigned char buffLEN, unsigned char *buffADDR);
void sendAT(unsigned char *buf);
bit COMP_buff2buff( unsigned char *BUFF1, unsigned char *BUFF2, unsigned char LEN);
void delay(void);
bit OKay( unsigned char *BUFF1, unsigned char *BUFF2, unsigned char LEN);
void confirmOK();

unsigned char rcx[13];
unsigned char txtMOD[]="AT+CMGF=1\r";
unsigned char TE_com[]="AT+CSCS=\"GSM\"\r";
unsigned char MOBnum[]="AT+CMGS=\"+2349056777712\"\r";
bit RXDcmpt;  //this flag is set if end of a string is detected.
bit PBflag;   //this flag is set when the MCU gets PB ready message.
unsigned char i,  rxd_cnt = 0;  //counts as value are recieved in the serrial ISR.
unsigned char SERIALcase ;    //switch case in ISR.
unsigned char *loc;

void main()
{
        //INITIALIZATION
                SCON = 0x50;
                TMOD = 0x20;
                TH1 = 0xFD;
                TR1 = 1;
                ES = 1;
                EA = 1;
                SERIALcase = 1; //set the default of the serial switch case in ISR.
                PBflag = rxd_cnt = RXDcmpt = 0;   //set flag to default.
                        while(!PBflag)
                {
                        if(RXDcmpt)   //Check if MCU recieved a value
                        {
                                confirmPBready(); //Check if its PBready.
                                if(!PBflag)
                                { rxd_cnt = 0;
                                        BYTEwrite(0x00,rxd_cnt,rcx);
                                        RXDcmpt = 0;
                                }
                        }
                }
                BYTEwrite(0x0,rxd_cnt,rcx);     //clear buffer
                rxd_cnt= PBflag = RXDcmpt = 0;
                //PBready recievd. Proceed with confirguration.

                sendAT(txtMOD);
                while(!PBflag)
                {
                        if(RXDcmpt && !PBflag)  //Check if MCU recieved a value
                                confirmOK();    //Check if its OK.
                }
                rxd_cnt = PBflag = RXDcmpt = 0;
                BYTEwrite(0,sizeof(rcx),rcx);
                //Command "AT+CMGF=1" receives OK 

                sendAT(TE_com);
                while(!PBflag)
                {
                        if(RXDcmpt && !PBflag)  //Check if MCU recieved a value
                                confirmOK();    //Check if its OK.
                }
                rxd_cnt = PBflag = RXDcmpt = 0;
                BYTEwrite(0,sizeof(rcx),rcx);
                //Command AT+CSCS=\"GSM\" receives OK

                sendAT(MOBnum);
                for(i = 1; i<30; i++)
                delay();
                sendAT("GSM MODULE TEXT VIA CODING");
                for(i = 1; i < 30 ; i++)
                delay();
                sendAT("0x1A");
                for(i = 1; i<60; i++)
                delay();
}

void delay(void)
{
        unsigned int i;
        for(i=0;i<25000;i++);
}

void BYTEwrite( unsigned char VAL, unsigned char buffLEN, unsigned char *buffADDR)
{
        while(buffLEN)
        {
                *buffADDR++ = VAL;      //write the value into address.
                buffLEN--;              //decrement the lenght
        }
        return;
}

bit COMP_buff2buff( unsigned char *BUFF1, unsigned char *BUFF2, unsigned char LEN)
{
                while(LEN)
                {
                if(*BUFF1++ != *BUFF2++) //Check if both value in address are same.
                        {
                                RXDcmpt = 0;
                                return 0;       //One value is different.
                        }
                        LEN--;                  //Decrement.
                }
//AT Last, all values are the same in both buffers.
return 1;
}

void confirmPBready()
{
 if(COMP_buff2buff(rcx,"+PBREADY", rxd_cnt)) //Check if the value recieved is PBready
        {PBflag = 1;                            //YES. So set flag.
        }
        return;
}

void confirmOK()
{
     if( COMP_buff2buff(rcx ,"OK", rxd_cnt))//Check if the value recieved is PBready
                PBflag = 1;                      //YES. So set flag.
        return;
}

void serial(void) interrupt 4
{
        unsigned char RXD_VAL;
        RXD_VAL = SBUF;

if(RI)
{
  switch(SERIALcase)
   {
     case 1:
        if(RXD_VAL == 0x0D)
        {//clear the buffer if the value is 0x0D
        SERIALcase=2;
        }
        break;
        case 2:
        if(RXD_VAL == 0x0A)
        {//clear the buffer if the value is 0x0A
        SERIALcase = 3;                         // buffer must receive OD n OA first 
        }
        break;
        case 3:
        if(RXD_VAL == 0x0D)
    {//the next character should be 0x0A.
        SERIALcase  = 4;        //check for 0x0A.
        }
        else
        {
        rcx[rxd_cnt++] = RXD_VAL;       //save the value recieved in rcx buffer
        }
        break;
        case 4:
        if(RXD_VAL == 0x0A)
        {//If 0x0A is recieved after 0x0D, then this is the end of recieve frame.
        RXDcmpt = 1;    //set recieve complete flag. 
        }
       else
        {
        rcx[rxd_cnt++] = RXD_VAL;    //save the value recieved in rcx buffer
                                                }
       SERIALcase  = 1;
      //its not 0x0A, so go back to keep recieveing till you detect another 0x0D.
       break;
       }
      }
   RI = 0;
}


void sendAT(unsigned char *buf)
{
        while(*buf)
        {
                SBUF = *buf++;
                while(!TI);
                TI=0;
        }

}