// Infra Red soft transmitter to IR receiver on COM port of PC at 9600 Baud 
#define TXEN 3
#define URSEL 7
#define USBS 3
#define UCSZ0 1
#define UDRE 5 

void send_byte(char byte)   // 8 impulses at 38 kHz carrier frequence
{       char i;
        int delay; 
        char j;
               
        for(j=0; j<4; j++)       // 4
                        {       UDR=0x55;   // START IMPULSE 
                                while((UCSRA&(1<<UDRE))==0);                                
                        };         
                  
        for(i=0; i<8; i++)
          { 
                if(byte&0x01==0x01) 
                {        for(delay=440; delay>0; delay-- ) ;   // NO CARRIER -> BIT = 0
                }        
                else 
                {       
                 for(j=0; j<4; j++)       // 4
                        {       UDR=0x55;   // IS CARRIER -> BIT = 1
                                while((UCSRA&(1<<UDRE))==0);                                
                        };  
                }                 
                byte>>=1;
          }; 
   while((UCSRA&(1<<UDRE))==0);            
 for(delay=1000; delay>0; delay-- ) ;   // STOP BIT         

} 

 void tx_ena(void)
 {
                UBRRH=0;
                UBRRL=5;               // 5=76800  BIT/SEC
                UCSRB=(1<<TXEN);
                UCSRC=(1<<URSEL); 
                UCSRC=(1<<URSEL)|(0<<USBS)|(1<<UCSZ0); // 1 STOP BIT,  8 DATA BITS,  NO PARITY
  }

void send_to_pc(void)   // 9600 bit per second soft transmitter
{                       // 0ne bit sends one byte 0x55 at 76800 bit =
 char byte;             // 8 impulses at 38 kHz carrier frequence
 char i=0;
 char j=0; 
 int delay;
 
     for(j=0; j<40; j++)                        // INIT AGC IN IR RECEIVER
          {     UDR=0x55;                       // PREAMBLE 1 IMPULSE 
                while((UCSRA&(1<<UDRE))==0);                 
          }; 
        while((UCSRA&(1<<UDRE))==0);    
        for(delay=3000; delay>0; delay-- ) ;          // PREAMBLE 0 IMPULSE 
  
 do 
 {                                             // 10 BYTES OF CURRENT NANOVOLTMETER VALUE
 byte=adc_string[i];
 send_byte(byte);
 i=i+1;
 }
 while(adc_string[i]);
 while((UCSRA&(1<<UDRE))==0);                 // send CR LF
 send_byte(0x0A);
 while((UCSRA&(1<<UDRE))==0);      
 send_byte(0x0D);
    
}