hwa/atmel/avr/examples/03-6-fade-counter-compare-output/main.c

Fade a LED connected to a counter compare output (method 2).

Changes versus method 1:

• define PWM as hw_ocXY and use (PWM,counter) to retrieve the name of the counter;
• use a HWA context in the ISR and the couple hwa_nocommit() / hwa_commit() to write the changes to the hardware;
• use a seperate function to store the hardware configuration into a HWA context.

 
/*  This file is part of the HWA project.
 *  Copyright (c) 2012,2015 Christophe Duparquet.
 *  All rights reserved. Read LICENSE.TXT for details.
 */
 
#include BOARD_H
 
 
/*  The counter
 */
#define PWM                     (counter0,compare0)
#define CLKDIV                  64
#define COUNTMODE               up_loop
#define TOP                     0xFF
 
/*  Compare strings
 */
#define STRCMP(s1,s2)           __builtin_strcmp(s1,s2)
 
 
/*  Store the hardware configuration into a HWA context
 */
HW_INLINE void setup_hwa_context ( hwa_t *hwa )
{
  /*  Have the CPU enter idle mode when the 'sleep' instruction is executed.
   */
  hwa( configure,  core0,
       sleep,      enabled,
       sleep_mode, idle );
 
  /*  Configure the counter to count between 0 and 0xFF
   */
  hwa( configure, (PWM,counter),
       clock,     ioclk / CLKDIV,
       direction, COUNTMODE,
       bottom,    0,
       top,       TOP );
 
  if ( !STRCMP(HW_Q(COUNTMODE),"updown_loop") )
    hwa( configure, PWM, output, clear_after_match_up_set_after_match_down );
  else /* up_loop */
    hwa( configure, PWM, output, set_at_bottom_clear_after_match );
 
  /*  Enable overflow IRQ
   */
  hwa( enable, (PWM,counter,irq,overflow) );
}
 
 
/*  Service the counter overflow IRQ: compute the next value of the compare unit
 *
 *    Phase 0: increase duty cycle from 0 to 255
 *    Phase 1: decrease duty cycle from 255 to 0 (use ~duty)
 *    Phase 2: off
 *    Phase 3: off
 */
HW_ISR( (PWM,counter,irq,overflow) )
{
  static uint8_t        duty ;
  static uint8_t        phase ;
 
  if ( phase == 0 )
    hw( write, PWM, duty );
  else if ( phase == 1 )
    hw( write, PWM, ~duty );
 
  duty++ ;
 
  if ( duty==0 ) {
    phase = (phase + 1) & 3 ;
 
    /*  In 'up_loop' counting mode, we must disconnect/reconnect the output of
     *  the compare unit as it can not provide pulses of less than 1 cycle.
     */
    if ( !STRCMP(HW_Q(COUNTMODE),"up_loop") ) {
 
      /*  Start from the hardawre configuration used at initialization
       */
      hwa( begin, reset );
      setup_hwa_context( hwa );
 
      if ( phase == 2 ) {
        /*
         *  Change the compare output config from 'set_at_bottom_clear_after_match'
         *  to 'disconnected'
         */
        hwa( configure, PWM, output, set_at_bottom_clear_after_match );
        hwa( nocommit );
        hwa( configure, PWM, output, disconnected );
        hwa( commit );
      }
      else if ( phase == 0 ) {
        /*
         *  Change the compare output config from 'disconnected' to
         *  'set_at_bottom_clear_after_match'
         */
        hwa( configure, PWM, output, disconnected );
        hwa( nocommit );
        hwa( configure, PWM, output, set_at_bottom_clear_after_match );
        hwa( commit );
      }
    }
  }
}
 
 
int main ( )
{
  /*  Create a HWA context to collect the hardware configuration
   *  Preload this context with RESET values
   */
  hwa( begin, reset );
 
  /*  Store the hardware configuration into the HWA context
   */
  setup_hwa_context( hwa );
 
  /*  Write this configuration into the hardware
   */
  hwa( commit );
 
  hw( enable, interrupts );
 
  for(;;)
    hw( wait, irq );
}