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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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