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Friends I am trying to interface AT89S52 microcontroller with SIM900 modem without the use of PC with the code
#include<reg51.h>
#define port P1
#define dataport P2 // Data port for LCD
sbit rs = port^2;
sbit rw = port^3;
sbit en = port^4;
int count,i;
unsigned char check,str[15];
bit check_space;
void init_serial() // Initialize serial port
{
TMOD=0x20; // Mode2
TH1=0xfd; // 9600 baud
SCON=0x50; // Serial mode=1 ,8-Bit data,1 Stop bit ,1 Start bit, Receiving on
TR1=1; // Start timer
}
void delay(unsigned int msec) // Function for delay
{
int i,j;
for(i=0;i<msec;i++)
for(j=0; j<1275; j++);
}
void lcd_cmd(unsigned char item) // Function to send command on LCD
{
dataport = item;
rs= 0;
rw=0;
en=1;
delay(1);
en=0;
return;
}
void lcd_data(unsigned char item) // Function to display character on LCD
{
dataport = item;
rs= 1;
rw=0;
en=1;
delay(1);
en=0;
return;
}
void lcd_data_string(unsigned char *str) // Function to display string on LCD
{
int i=0;
while(str!=' ')
{
lcd_data(str);
i++;
delay(10);
}
return;
}
void lcd()
{
lcd_cmd(0x38); // For using 8-bit 2 row LCD
delay(5);
lcd_cmd(0x0F); // For display on cursor blinking
delay(5);
lcd_cmd(0x80); // Set the cursor on first position of LCD
delay(5);
}
void transmit_data(unsigned char str) // Function to transmit data through serial port
{
SBUF=str; //Store data in SBUF
while(TI==0); //Wait till data transmits
TI=0;
}
void receive_data() interrupt 4 // Function to recieve data serialy from RS232 into microcontroller
{
RI=0;
str[++count]=SBUF; //Read SBUF
}
unsigned char byte_check() // Function to check carraige return and new line character
{
switch(str[0])
{
case 0x0a:
{ // Return 0x00 for new line
return 0x00;
break ;
}
case 0x0d:
{ // Return 0x01 for carriage return
return 0x01;
break ;
}
default :return 0x02 ; // Return 0x02 for characters except new line and carriage return
}
}
void main()
{
lcd(); // Initialize LCD
init_serial(); // Initialize serial port
count=(-1);
delay(500);
lcd_data_string("Ready");
delay(10);
lcd_cmd(0x01);
IE=0x94;
transmit_data('A'); // Transmit 'A' to serial port
delay(1);
transmit_data('T'); // Transmit 'T' to serial port
delay(1);
transmit_data(0x0d); // Transmit carriage return to serial port
delay(50);
while(1)
{
if(count>=0)
{
check=byte_check(); // Check the character
if(check!=0x00)
{
if(check==0x01)
{
if(check_space==1) // Check previous character
{
lcd_data(0x20);
check_space=0;
}
}
else
{
lcd_data(str[0]);
check_space=1;
}
}
count--;
for(i=0;i<count;i++) // Shift the whole array to one left
{
str=str[i+1];
}
}
}
}as mentioned in the same website. But I am not getting the required result, that is I am not getting any message from the GSM module hence please help me with it ( considering me as a pure fressher )
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