AVR Freaks

Hi 

I am very confused to communicate between sim800 and xmega in Atmel Studio 6.2, I set baud rate 9600 and use USARTD on PORTD it works fine in one xmega but it may be lost because of VCC gnd short circuit, I use another one but send is ok and sms can send by my command to sim800 but when I want to receive data it does not work properly and receive "AT" instead of my sms. here is the code of usart initial and clock set to 32mhz internal:

    PORTD.DIRSET   = PIN7_bm;
    PORTD.DIRCLR   = PIN6_bm;
    USARTD1_BAUDCTRLA=0xCF; //for baud rate 9600, BSEL=12, BSCALE=4 as per data sheet
    USARTD1_BAUDCTRLB=0x00; //BSCALE=4, upper 4 bits out of 12 bit used for USART baud rate setting will be zero
    USARTD1_CTRLB|=USART_RXEN_bm|USART_TXEN_bm; //enable USART receiver and transmitter
    USARTD1_CTRLC|=USART_CHSIZE1_bm|USART_CHSIZE0_bm; //asynchronous mode, 8-bit character size, 1 stop bit, no parity

sms receive code:

for (sms_n=0;sms_n<=100;sms_n++){
 sms[sms_n]=Null;}

 end_message=0;sms_n=0;

 sendString("AT+CMGF=1\n\r");_delay_ms(250);
 sendString("AT+CMGR=1\n\r");_delay_ms(1000);
 sendString("AT+CMGR=1\n\r");
 //read sms

 while(end_message==0)
 {
 rec=usart_receiveByte();
   if(rec==Null)
   {
   }

   else if (((rec==LF || rec==CR)) && sms[1]!=Null)
   {
	   end_message=1;
   }

   else
   {
	   if(sms_n>=100)
	   {
	   }
	   else
	   {
		sms[sms_n]=rec;
		sms_n++;
	   }
     }
 }

and receive function:

char usart_receiveByte()
{
    while( !(USARTD1_STATUS & USART_RXCIF_bm) );
    return USARTD1_DATA;
}

I tested my sim800 with Arduino Uno it works perfectly.