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//#define  PTT PIN_A2                 // PTT control
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//#define  TXo PIN_C0                 // To the transmitter modulator
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//#define  PERIODAH delay_us(218)     // Halfperiod H 222;78/1200     500;430/500
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//#define  TAILH delay_us(74)
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//#define  PERIODAL delay_us(408)     // Halfperiod L 412;345/1200    1000;880/500
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//#define  TAILL delay_us(341)
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#define  PERIODAH delay_us(222)     // Halfperiod H 222;78/1200     500;430/500
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#define  TAILH delay_us(78)
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#define  PERIODAL delay_us(412)     // Halfperiod L 412;345/1200    1000;880/500
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#define  TAILL delay_us(345)
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#byte    STATUS = 3                 // CPUs status register
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byte SendData[16] = {'A'<<1, 'L'<<1, 'L'<<1, ' '<<1, ' '<<1, ' '<<1,  0x60,
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                     'C'<<1, 'Z'<<1, '0'<<1, 'R'<<1, 'R'<<1, 'R'<<1, 0x61,
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                     0x03, 0xF0};
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boolean bit;
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int fcslo, fcshi;    // variabloes for calculating FCS (CRC)
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int stuff;           // stuff counter for extra 0
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int flag_flag;       // if it is sending flag (7E)
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int fcs_flag;        // if it is sending Frame Check Sequence
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int i;               // for for
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void flipout()       //flips the state of output pin a_1
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{
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	stuff = 0;        //since this is a 0, reset the stuff counter
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	if (bit)
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   {
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     bit=FALSE;      //if the state of the pin was low, make it high.
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   }
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   else
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   {
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     bit=TRUE;	  	   //if the state of the pin was high make it low
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   }
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}
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void fcsbit(byte tbyte)
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{
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#asm
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   BCF    STATUS,0
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   RRF    fcshi,F             // rotates the entire 16 bits
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   RRF    fcslo,F			      // to the right
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#endasm
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   if (((STATUS & 0x01)^(tbyte)) ==0x01)
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   {
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         fcshi = fcshi^0x84;
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         fcslo = fcslo^0x08;
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   }
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}
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void SendBit ()
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{
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	if (bit)
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   {
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      output_low(TXo);
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      PERIODAH;
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      output_high(TXo);
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      PERIODAH;
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      output_low(TXo);
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      PERIODAH;
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      output_high(TXo);
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      TAILH;
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    }
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    else
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    {
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      output_low(TXo);
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      PERIODAL;
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      output_high(TXo);
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      TAILL;
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    };
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}
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void SendByte (byte inbyte)
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{
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   int k, bt;
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   for (k=0;k<8;k++)    //do the following for each of the 8 bits in the byte
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   {
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     bt = inbyte & 0x01;            //strip off the rightmost bit of the byte to be sent (inbyte)
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     if ((fcs_flag == FALSE) & (flag_flag == FALSE)) fcsbit(bt);    //do FCS calc, but only if this
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						                                                //is not a flag or fcs byte
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     if (bt == 0)
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     {
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       flipout();
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     }  			               // if this bit is a zero, flip the output state
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     else
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     {                          			      //otherwise if it is a 1, do the following:
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       if (flag_flag == FALSE) stuff++;      //increment the count of consequtive 1's
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       if ((flag_flag == FALSE) & (stuff == 5))
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       {       //stuff an extra 0, if 5 1's in a row
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         SendBit();
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         flipout();               //flip the output state to stuff a 0
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       }//end of if
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     }//end of else
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     // delay_us(850);				 //introduces a delay that creates 1200 baud
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     SendBit();
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     inbyte = inbyte>>1;          //go to the next bit in the byte
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   }//end of for
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}//end of SendByte
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void SendPacket(char *data)
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{
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    bit=FALSE;
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   fcslo=fcshi=0xFF;       //The 2 FCS Bytes are initialized to FF
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   stuff = 0;              //The variable stuff counts the number of 1's in a row. When it gets to 5
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		                     // it is time to stuff a 0.
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//   output_low(PTT);        // Blinking LED
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//   delay_ms(1000);
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//   output_high(PTT);
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   flag_flag = TRUE;       //The variable flag is true if you are transmitted flags (7E's) false otherwise.
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   fcs_flag = FALSE;       //The variable fcsflag is true if you are transmitting FCS bytes, false otherwise.
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   for(i=0; i<10; i++) SendByte(0x7E); //Sends flag bytes.  Adjust length for txdelay
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                                       //each flag takes approx 6.7 ms
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   flag_flag = FALSE;      //done sending flags
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   for(i=0; i<16; i++) SendByte(SendData[i]);      //send the packet bytes
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   for(i=0; 0 != *data; i++)
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   {
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      SendByte(*data);     //send the packet bytes
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      data++;
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   };
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   fcs_flag = TRUE;       	//about to send the FCS bytes
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   fcslo =fcslo^0xff;      //must XOR them with FF before sending
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   fcshi = fcshi^0xff;
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   SendByte(fcslo);        //send the low byte of fcs
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   SendByte(fcshi);        //send the high byte of fcs
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   fcs_flag = FALSE;		   //done sending FCS
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   flag_flag = TRUE;  		//about to send flags
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   SendByte(0x7e);         // Send a flag to end packet
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}
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