[SOLVED] GSM SIM900 with lpc2148

char get_char()
{
       while(!(U0LSR & 0x01));//Wait until UART0 gets sum char  
       return U0RBR;
}

int main()
{
	lcd_init();
	USARTInit();
	while(1)
	{	
		send_char('A');
		send_char('T');
		send_char(0x0d); //carriage return
		
		soft_delay_ms(50);
		if(!CheckGSM_Response())
		{
			continue;
		}
	}	
}
//code to send_char()

//code to receive
unsigned char buff[16];
unsigned char receive_char()
{
	int i=0;
	while(!(U0LSR&0x01));
	return U0RBR;
}	

int CheckGSM_Response()
{
		int i=0;
		int len=0;
		char data=0;
		//soft_delay_ms(10);
		while(data!='\r')
		{
			len++;
			data=receive_char();
			buff[i++]=data;
		}
		buff[i-1] = '\0';
		if(buff[0]!=0x0D | buff[1]!=0x0A)
		{	
			return 0;
		}
		if(buff[len]!=0x0D | buff[len-1]!=0x0A)
		{	
			return 0;
		}
		if((buff[2]!='O'||buff[2]!='o')&&(buff[3]!='K'||buff[3]!='k'))
		{	
			return 0;
		}	
		gotoloc(2,1);
		LCD_WriteString("received OK");
		return (1);			 		  
}

//code for uartinit()

while(data!='\r')
		{
			len++;
			data=receive_char();
			buff[i++]=data;
		}

while(!(U0LSR&0x01));
	return U0RBR;

#include<lpc214x.h>
#include<stdlib.h>
#include<string.h>
#include<stdio.h>
#include "lcd.h"

void send_string(char *p);//Sends a string of data through UART1
void send_char(char data);
void USARTInit(void);
unsigned char receive_char(void);

int main()
{
	char ch[16]="";
	int i=0;
	lcd_init();
	USARTInit();
	gotoloc(1,1);
	LCD_WriteString("welcome to gsm");
	soft_delay_ms(1000);
	while(1)
	{	
		LCD_Cmd(0x01);
		soft_delay_ms(100);
		//sending AT command
		LCD_WriteString("sending AT");
		
		U0FCR=0x04;
		send_char('A');
		soft_delay_ms(10);
		send_char('T');
		//soft_delay_ms(10);
		send_char(0x0d); //carriage return
		while(ch[i]!='\r')
		{
			ch[i]=receive_char();
			
			LCD_Write_DATA(ch[i++]);
		}	
		//send_char(0x0a);//line feed
	}	
}

void send_char(char data)
{
	while(!(U0LSR&0x20));
	U0THR=data;
}

void send_string(char *p)            //Sends a string of data through UART1
{
	while(1)
	{
		if(*p=='\0')
			break;
		send_char(*p++);
	}
}

unsigned char receive_char()
{
	while(!(U0LSR&0x01));
	gotoloc(2,1);
	LCD_WriteString(" 2 ");
	return U0RBR;
}	

void USARTInit()
{
	PINSEL0 = 0x00000005;  //Select TxD    for     P0.0 and RxD for P0.1
  U0LCR   = 0x83;// 8 bits, no Parity, 1 Stop bit  
	U0DLM   = 0x00;
	U0DLL   = 0x61;
	U0FCR	  = 0X07;//ENABLE FIFO
	U0TER   = 0X80;
	U0LCR   = 0x03;//to lock mul  and div value

}