const unsigned short  one_high =1200;                //1.2ms
const unsigned short  one_low =600;                  //0.6ms
const unsigned short  zero_high =600;
const unsigned short  zero_low  =600;
const unsigned short  Start_Pulse = 2400;
const unsigned short  Start_Pulse_low = 600;
const unsigned short  Space_between_Pulses = 2750;  //27.5 ms
unsigned short i,x,y,dbit=0;
//==============================================================
void send_Start_Pulse() {
     portb.f0=1;delay_us(Start_Pulse);
     portb.f0=0;delay_us(Start_Pulse_low);
}
void send_1() {
     portb.f0=1;delay_us(one_high);
     portb.f0=0;delay_us(one_low);
}
void send_0() {
     portb.f0=1;delay_us(zero_high);
     portb.f0=0;delay_us(zero_low);
}
void main() {
  PORTB = 0;
  TRISB = 0;
  trisa=0xff;
  cmcon=0x07;
  while (1) {
  portb.f0=1;delay_ms(50);portb.f0=0;delay_ms(50);

  if (porta.f2==1){delay_ms(250);
  for(y=0;y<2;y++){ send_Start_Pulse();
                    send_1();
                    for(x=0;x<6;x++){send_0();}
                    send_1();
                    delay_ms(20); }
                   }

  if (porta.f3==1){delay_ms(250);
  for(y=0;y<2;y++){send_Start_Pulse();
                   send_1();send_1();
                   for(x=0;x<5;x++){send_0();}
                   send_1();
                   delay_ms(20); }
                   }
  if (porta.f1==1){delay_ms(250);
  for(y=0;y<2;y++){ send_Start_Pulse();
                    send_1();send_1(); send_1();
                    for(x=0;x<4;x++){send_0();}
                    send_1();
                    delay_ms(20); }
                   }

  if (porta.f0==1){delay_ms(250);
  for(y=0;y<2;y++){send_Start_Pulse();
                   send_1();send_1();send_1();send_1();
                   for(x=0;x<3;x++){send_0();}
                   send_1();
                   delay_ms(20); }
                   }
  }
 }

case 1: Portb.F0 = ~Portb.F0;Delay_ms(250);break;        // button TV '0'
                case 2: Portb.F1 = ~Portb.F1;Delay_ms(250);break;        // button TV '1'
                case 3: Portb.F2 = ~Portb.F2;Delay_ms(250);break;        // button TV '0'
                case 4: Portb.F3 = ~Portb.F3;Delay_ms(250);break;