Synchronous pulses

[Mike, K8LH]

Hi Andrew,

Would you like me to describe one method for producing up to 8 precisely timed synchronous pulses (on a single port), each pulse with a pulse width value of from 0 (off) to 1023 usecs with 1 usec pulse width resolution? If so, please let me know and I'd be happy to explain how the following code snippets work. I apologize for the C code.

Kind regards, Mike

unsigned int pulse[] = {  120,       // pulse 0 (RB0),  120-usecs
                           44,       // pulse 1 (RB1),   44-usecs
                           45,       // pulse 2 (RB2),   45-usecs
                         1001,       // pulse 3 (RB3), 1001-usecs
                            0,       // pulse 4 (RB4), off/not used
                            0,       // pulse 5 (RB5), off/not used
                            0,       // pulse 6 (RB6), off/not used
                            0 };     // pulse 7 (RB7), off/not used

unsigned char toggle[1024] @0x400    // 1024 element (interval) toggle array

//
//  1024 interval output routine (BoostC compiles the following
//  do-while code into a 5-cycle loop which is perfect for 1-usec
//  intervals with a 20-MHz clock).
//
void Output()
{ fsr0 = 0x400;                      // interval = 0
  do                                 // do
  { latb ^= postinc0;                // { latb ^= toggle[interval++]
  } while(fsr0h.3 == 0);             // } while(interval < 1024)
}

//
//  build new toggle array from the pulse array before calling Output()
//
void PrepArray()
{ for(i = 0; i < 1024; i++)          //
    toggle[i] = 0;                   // clear the array
  toggle[pulse[0]] |= 1;             // insert RB0 output toggle bit
  toggle[pulse[1]] |= 2;             // insert RB1 output toggle bit
  toggle[pulse[2]] |= 4;             // insert RB2 output toggle bit
  toggle[pulse[3]] |= 8;             // insert RB3 output toggle bit
  toggle[pulse[4]] |= 16;            // insert RB4 output toggle bit
  toggle[pulse[5]] |= 32;            // insert RB5 output toggle bit
  toggle[pulse[6]] |= 64;            // insert RB6 output toggle bit
  toggle[pulse[7]] |= 128;           // insert RB7 output toggle bit
  toggle[0] ^= 0xFF;                 // fix toggle[0] element
}