hwa/atmel/avr/examples/03-4-blink-counter-compare-irq/main.c

Blink a LED using a counter compare interrupt

 
/*  This file is part of the HWA project.
 *  Copyright (c) 2012,2015 Christophe Duparquet.
 *  All rights reserved. Read LICENSE.TXT for details.
 */
 
/*  Include the target board (and device) definitions
 */
#include BOARD_H
 
 
/*  The counter
 */
#define COUNTER                 counter0
#define CLKDIV                  64
#define COUNTMODE               up_loop
#define COMPARE                 compare0
#define PERIOD                  0.5
 
/*  Compare strings
 */
#define STRCMP(s1,s2)           __builtin_strcmp(s1,s2)
 
 
/*  Service the compare-match IRQ
 */
HW_ISR( (COUNTER,COMPARE,irq) )
{
  hw( write, COUNTER, 0 );
 
  static uint8_t n ;
  n++ ;
  if ( n >= (uint8_t)(0.5 + 1.0 * PERIOD / 2.0 / 0.001) ) {     /* Added 0.5 for rounding */
    n = 0 ;
    hw( toggle, PIN_LED );
  }
}
 
 
int main ( )
{
  /*  Create a HWA context to collect the hardware configuration
   *  Preload this context with RESET values
   */
  hwa( begin, reset );
 
  /*  Configure the LED pin
   */
  hwa( configure, PIN_LED, mode, digital_output );
 
  /*  Have the CPU enter idle mode when the 'sleep' instruction is executed.
   */
  hwa( configure,  core0,
       sleep,      enabled,
       sleep_mode, idle );
 
  /*  Configure the compare unit to match every 0.001 s.
   */
  hwa( configure, COUNTER,
       clock,     ioclk / CLKDIV,
       direction, COUNTMODE,
       bottom,    0,
       top,       max );
 
  /*  FIXME: should subtract 1 from the compare value because the compare match
   *  flag is set one counting cycle after the match.
   */
  if ( !STRCMP(HW_Q(COUNTMODE),"updown_loop") )
    hwa( write, (COUNTER,COMPARE), 0.5 + 0.001*HW_SYSHZ/CLKDIV/2 );
  else /* up_loop */
    hwa( write, (COUNTER,COMPARE), 0.5 + 0.001*HW_SYSHZ/CLKDIV );
 
  /*  Enable compare IRQ
   */
  hwa( enable, (COUNTER,COMPARE,irq) );
 
  /*  Write this configuration into the hardware
   */
  hwa( commit );
 
  hw( enable, interrupts );
 
  for(;;)
    hw( wait, irq );
}