jappelino

The receive routine is based on two states: either looking for a device or sampling data from a found device.
There is also a timeout in case a sensors is not transmitting.

void read_port(unsigned char item){

  unsigned char p = 0xFF;
  long delay;
  unsigned char a;
  char b=0;
  unsigned char d = 0 ;
  unsigned char search = 0x17;
 
  int e;
 
  int t = 0;
 
  BCSCTL1 |= RSEL3 | RSEL2 | RSEL1 | RSEL0; // increase speed
  P1DIR = 0xF4;                            // Set P1.2 to output direction
  P1OUT = 0xF8;   // set p1.2 low to leave snooze mode set p1.3 high to mark sample point
 
  TACTL = 0x1E4;    // start timer ACLK /8 continuous mode
 
  for( e = 0; e < 5000 ; e++); // wait to awake from snoze
 
  hit = 0;    // reset hit marker

  while(t < 1500 & hit == 0){

    t = TAR;
   
    d = 0;
 
    p = 0x17;
 
    while(p != 0){   // wait for startbit

      p = P1IN;
 
      p &= 0x02;
 
    }

    delay = 15;

    while(delay > 1)  // half bit extra delay at start
      delay--;
    for(a = 8; a > 0 ; a--){
 
      delay = 33;

      while(delay > 1)
        delay--;

      d = d  >> 1;
 
      P1OUT = 0xF8; // set sample pin

      p = P1IN;
              
      p &= 0x02;
 
      p = p << 6;     // LSB first

      d |= p;
     
    } // one byte ready
//send_char(d);
//BCSCTL1 |= RSEL3 | RSEL2 | RSEL1 | RSEL0; // increase speed
        
    if((search == 0x17) & (d == (0x41 + item ))){
     
      search = 0x16;
     
    } 

    else if(search == 0x16){

      buffer[b++] = d;
     
      if( b > size[item])
        hit = 0x17;
               
    } // end of char 
    delay = 15;

    while(delay > 1)  // half bit extra delay at end
      delay--;
         
  }  // end of timeout
  BCSCTL1 = RSEL2 | RSEL1 | RSEL0; // reduce speed 
  P1OUT = 0xF4;  // set P1.2 high to enter snooze mode
 
}