Getting string from UART

[Qutbuddin]

Hi Everyone,
I am doing a project using gsm. I want to receive string from UART and compare it with the predefined string.But somehow I am not able to get string from UART. Below is my code

void recieve_string()
{ unsigned char p;
while(RI!=0)
{
p=SBUF;
z=p;
i++;
}while(p!='\0');

RI=0;
compare_string();
}


void compare_string()
{
if(strcmp(z,a)==0){
relay=1;
}
else if(strcmp(z,b)==0){
relay=0;
}

 

[thegioi21master]

Which microcontroller ?

 

[Qutbuddin]

I am using at89s52.

 

[thegioi21master]

// Program to test serial communication of controller with PC using hyper terminal
#include<reg51.h>

void ini()     // Initialize Timer 1 for serial communication
{
TMOD=0x20;  //Timer1, mode 2, baud rate 9600 bps
TH1=0XFD; 
SCON=0x50;
TR1=1;
}

void recieve()  //Function to receive serial data
{
unsigned char value;
while(RI==0);
value=SBUF;
P1=value;
RI=0;
}

void transmit()  // Funtion to transmit serial data
{
P2=P1-32;
SBUF=P2;
while(TI==0);
TI=0;
SBUF=P1;
while(TI==0);
TI=0;
}

void main()
{
while(1)
{
  ini();
  recieve();
  transmit();
}
}

 

[Qutbuddin]

This will read only a single byte from uart but i want read an array of string.

 

[thegioi21master]

Edit receive() following:

char recieve()  //Function to receive serial data
{
unsigned char value;
while(RI==0);
value=SBUF;
P1=value;
RI=0;
return value
}

Add this function:

void UReadBuffer(void *buff,int len)
{
	int i;
	for(i=0;i<len;i++)
	{
		((char*)buff)[i]=recieve();
	}
}

 

[Qutbuddin]

Thanks for the help.Now I want to compare array of the received string with that of predefined string.Can you please help me with the same ?

 

[Surender Reddy]

Thanks for the help.Now I want to compare array of the received string with that of predefined string.Can you please help me with the same ?

First know the string length, then it is easy.
Try this one, it will help you

int b=0;                   //initialize b
for(int i=0;i<5;i++)  //string length is 5
{
   if(a[i]==x[i])    //here a[] is the string which is received through uart and x[] is predefined string
   {
      b++;        //increment b value by one
   }
}
if(b==5)
{
 //write your output
}