#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <string.h>

#define buffer_size 64

void usart_init(unsigned int value);
void transmit_char(char cmd);
void transmit_string(char * cmd);
void blinkLed();

char buffer[buffer_size];
uint8_t readpos = 0;
uint8_t writepos = 0;



int main(void)
{
    _delay_ms(1000);
    DDRB = 0x01;

    blinkLed();
    usart_init(103);
    sei();
    readpos = 0;
    writepos = 0;
  
    while (1)
    {
        if (strstr(buffer,"2200BE2EE052"))
         {blinkLed(); writepos=0;}
    }
}

void blinkLed()
{
    PORTB=0xfe;
    _delay_ms(1000);
    PORTB=0x01;
    _delay_ms(1000);
}

void usart_init(unsigned int value)
{
    UBRRH = (value>>8);
    UBRRL = value;
  
    UCSRB |= (1<<RXEN) | (1<<RXCIE);
    UCSRC |= (1<<UCSZ0) | (1<<UCSZ1) | (1<<URSEL);
  
}


ISR(USART_RXC_vect)
{
  
    buffer[writepos] = UDR;
    writepos++;
    if(writepos>=buffer_size)
    {
        writepos = 0;
      
        for(int i=0;i<buffer_size;i++)
        buffer[I] = 0;
       
    }
}

whats going wrong?

Moderators note : used code tags

 

Hardware?

Does the hardware work? how is it connected?

Code is only part of the puzzle.

 

yes perfectly checked via hyperterminal.

rmd6300 tx connected to atmega8 rx.

 

How is the USART setup with the call to
usart_init(103)? What is the Baud rate, databits, etc.?

 

And add to the list of unknowns:

What the MCU clock frequency?

 

Baud rate -9600
F_CPU-16Mh
8 data bit
Parity none

 

Does the first blinkLed() function call work correctly?

 

In one thread you use usart_init(103), in another you use usart_init(8), and in a third you use usart_init(6), what is the difference in USART setup?

 

I was just trying to check with diffrent bauds cuz i was not getting anything..and i had to submit project by tomorrow...

 

Yes first ledblink works.

 

Usart_init(103) suggest baud of 9600 at 16Mhz clock
Usart_init(8) suggest baud of 115200 at 16Mhz clock
And usart_init(6) suggest baud of 9600 at 1Mhz clock
I was using 1 mHz befor but then i set the fuse bit of atmega 8. And now i cn make it run on 16MHz external clock

 

I made a small project with a pir sensor.. which blinks led and switch on the fan as soon as it detects motion..i guess i have some problm with serial communication. And i vl try it after my exams. Thanks evry1 for your help.

 

Have you tried some other sites like: http://www.avrfreaks.net/forum/sendingrecevie-data-rs232-atmega8

 

Here is another site with a code example;
https://circuitdigest.com/microcont...nication-between-two-atmega8-microcontrollers

 

So you do have Hyperterm.

Write a quick test program on the Atmega8 to send a single character to Hyperterm.
Test to verify that you have the correct baud.

 

Code example with explanation of each segment:
http://extremeelectronics.co.in/avr...vr-microcontrollers-reading-and-writing-data/