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i am able to send msg from gsm to the mobile phone but am not able to receive data from the GSM. eg..in this code when i send AT to the gsm , i get garbage value on the LCD instead of OK..but with the hyperterminal, the communication is proper with both the 8051 and GSM.
#include<stdio.h> #include<at89x51.h> #define port P1 #define dataport P2 // Data port for LCD sbit rs = port^2; sbit rw = port^3; sbit en = port^4; int p; unsigned char msg[20]; //generates delay in milli seconds void delay_ms(unsigned int i) { unsigned int j; while(i-->0) { for(j=0;j<500;j++) { ; } } } void command(unsigned char dost) { dataport=dost; //put the value on pin rs=0; rw=0; en=1; //strobe the enable pin delay_ms(5); en=0; } void lcddisplay(unsigned char word) { dataport=word; //put the value on pin rs=1; rw=0; en=1; //strobe the enable pin delay_ms(5); en=0; } void lcd_data_string(unsigned char *str) // Function to display string on LCD { int i=0; while(str[i]!='\0') { lcddisplay(str[i]); i++; delay_ms(1); } return; } //Function to initialize RS232 Serial Port void serial_init() { SCON=0x50; //setup for 8-bit data TMOD=0x20; //setup timer 1 for auto-reload TH1=0xfd; //Baud Rate 9600 TL1=0xfd; TR1=1; //turn on timer 1 TI=1; //indicate ready to transmit } //This function displays a null-terminated string on the RS232 port void send_serial(unsigned char *s) { while(*s!=0x0) { SBUF=*s; while(!TI) { } TI=0; s++; } } int i; void tx0(unsigned char x) //send data to serial port 0 { EA=0; SBUF=x; while(TI==0); TI=0; EA=1; } void lcd() { command(0x38); // For using 8-bit 2 row LCD delay_ms(1); command(0x0F); // For display on cursor blinking delay_ms(1); command(0x80); // Set the cursor on first position of LCD delay_ms(1); } char receive(void) { // unsigned char m; while (RI != 1) {;} //wait to receive data msg[++p]=SBUF; // save value of data RI=0; return (msg[p]); } void main() { p=(-1); delay_ms(80); lcd(); delay_ms(50); serial_init(); //Initialize Serial port. while(1) { int m; send_serial(" AT"); delay_ms(400); tx0(0x0D); m=receive(); command(0x06); lcddisplay(m); } }