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/********************************************************************
 *                                                                  *
 *  Project: 12F683 Test v1                                         *
 *   Source: 12F683_Test_v1.c                                       *
 *   Author: Mike McLaren, K8LH                                     *
 *     Date: 19-Jun-08                                              *
 *  Revised: 25-Jun-08                                              *
 *                                                                  *
 *  Charlieplexed 20 LED Demo with 32 PWM levels per LED            *
 *                                                                  *
 *                                                                  *
 *      IDE: MPLAB 8.01 (tabs = 4)                                  *
 *     Lang: SourceBoost BoostC v6.87, Lite/Free version            *
 *                                                                  *
 *                                                                  *
 ********************************************************************/

#include <system.h>

#pragma DATA _CONFIG, _FCMEN_OFF&_IESO_OFF&_MCLRE_OFF&_WDT_OFF&_INTOSCIO

#pragma CLOCK_FREQ 8000000      //

//--< function prototypes >------------------------------------------
//--< type definitions >---------------------------------------------
//--< variables >----------------------------------------------------

unsigned char led[20];          // led matrix, pwm values 0..31

unsigned char shadow = 0;       // isr, trisio shadow register
unsigned char colpos = 1;       // isr, gpio column ring counter bit
unsigned char dcy = 15;         // isr, duty cycle counter, 0..31
unsigned char dc0 = 0;          // isr, row 0 (gp0) pwm value, 0..31
unsigned char dc1 = 0;          // isr, row 1 (gp1) pwm value, 0..31
unsigned char dc2 = 0;          // isr, row 2 (gp2) pwm value, 0..31
unsigned char dc3 = 0;          // isr, row 3 (gp4) pwm value, 0..31

unsigned char addr = (unsigned char) &led;

//--< defines >------------------------------------------------------

#define end_of_period dcy.5     // isr, end of 32 pwm steps
#define end_of_cycle colpos.6   // isr, end of 5 column update cycle

//--< main >---------------------------------------------------------

void main()
{ 
  osccon = 0b01110000;          // set 8 MHz INTOSC
  while(!osccon.HTS);           // wait 'til oscillator stable
  cmcon0 = 7;                   // comparator off, digital I/O
  ansel = 0;                    // a2d module off, digital I/O
  trisio = 0b00111111;          // set all pins to inputs
  gpio = 0;                     // set all output latches to '0'

//  setup 100 usec Timer 2 interrupts (8 MHz clock)

  pir1 = 0;                     // clear peripheral interrupt flags
  pie1 = 0;                     // clear peripheral interrupt enables
  pie1.TMR2IE = 1;              // set Timer 2 interrupt enable bit
  tmr2 = 0;                     // clear Timer 2 register
  t2con = 0b00000100;           // '0-------' unimplemented bit
                                // '-0000---' TOUTPS<3:0>, postscale 1
                                // '-----1--' TMR2ON, turn Timer 2 on
                                // '------00' T2CKPS<1:0>, prescale 1
  pr2 = 200-1;                  // 200 x 500-nsec 'ticks' = 100 usecs
  intcon = 0b11000000;          // '1-------' GIE, enable global ints
                                // '-1------' PEIE, enable peripheral ints
                                // '--0-----' T0IE, TMR0 ints disabled
                                // '---0----' INTE, off
                                // '----0---' GPIE, IOC disabled
                                // '-----000' T0IF/INTF/GPIF flags
//
//  simple led interface to pwm driver, duty cycle values of 0..31
//

  led[0] = led[19] = 1;         //
  led[1] = led[18] = 1;         //
  led[2] = led[17] = 4;         //
  led[3] = led[16] = 0;         //
  led[4] = led[15] = 0;         //
  led[5] = led[14] = 1;         //
  led[6] = led[13] = 1;         //
  led[7] = led[12] = 0;         //
  led[8] = led[11] = 1;         //
  led[9] = led[10] = 1;         //

  while(1)                      //
  {
  }
}

/********************************************************************/
/*  interrupt service routine                                       */
/********************************************************************/
/*                                                                  */
/*  100 usec Timer2 interrupts, 32 interrupts/column (3.2 msecs)    */
/*  for 32 pwm brightness levels. 160 interrupts (16 msecs) for a   */
/*  complete 5 column update cycle (62.5 Hz refresh rate).          */
/*                                                                  */
/*  led array duty cycle parameter values of 0..31 produce actual   */
/*  duty cycles of 0% to 20% per LED in 0.625% (100 usec) steps.    */
/*                                                                  */
/*  57 to 84 cycles or approximately 42% "overhead" (8 MHz clock)   */
/*                                                                  */
/********************************************************************/
void interrupt()
{ 
  if(dc0 == dcy)            // if row 0 duty cycle match
    shadow.0 = 0;           //   clear shadow bit (gp0)
  if(dc1 == dcy)            // if row 1 duty cycle match
    shadow.1 = 0;           //   clear shadow bit (gp1)
  if(dc2 == dcy)            // if row 2 duty cycle match
    shadow.2 = 0;           //   clear shadow bit (gp2)
  if(dc3 == dcy)            // if row 3 duty cycle match
    shadow.4 = 0;           //   clear shadow bit (gp4)
  dcy++;                    // increment duty cycle counter
  asm
  { movf    _colpos,W       //
    andwf   _shadow,W       // is the float bit required?
    btfss   _status,Z       // no, skip, else
    iorlw   0b00100000      // set the 'float' bit
    iorwf   _shadow,W       // pick up led bits
    iorwf   _colpos,W       // pick up column bit
    xorlw   0b00111111      // invert all
    movwf   _trisio         // update the column LEDs
  }

  if(end_of_period)         // if all 32 pwm steps complete
  { dcy = 0;                // reset duty cycle counter
    asm
    { bcf     _status,C     // shift column bit mask
      rlf     _colpos,F     //
      btfsc   _colpos,3     // if gp3 bit position
      rlf     _colpos,F     // shift to gp4 bit position
    }
    if(end_of_cycle)        // if all 5 columns have been updated
    { colpos = 1;           // reset colpos bit to column 0
      asm                   // reset led[] array address pointer
      { movlw   _led        //
        movwf   _addr       // addr = (unsigned char) &led
      }
    }
    shadow = 0b00010111;    // setup shadow (all row bits "on")
    gpio = colpos;          // setup output latch, only 1 bit high
    fsr = addr;             // setup new column pwm work variables
    dc0 = indf;             // row 0 (gp0) pwm value, 0..31
    fsr++;                  //
    dc1 = indf;             // row 1 (gp1) pwm value, 0..31
    fsr++;                  //
    dc2 = indf;             // row 2 (gp2) pwm value, 0..31
    fsr++;                  //
    dc3 = indf;             // row 3 (gp4) pwm value, 0..31
    addr = fsr + 1;         // save array address
  }
}