hwa/atmel/avr/examples/03-1-blink-counter-overflow-flag/main.c

Blink a LED using a counter overflow flag

 
/*  This file is part of the HWA project.
 *  Copyright (c) 2012,2015 Christophe Duparquet.
 *  All rights reserved. Read LICENSE.TXT for details.
 */
 
/*  Target
 */
#include BOARD_H
 
 
/*  The counter
 */
#define COUNTER                 counter0
#define CLKDIV                  64
#define COUNTMODE               up_loop
#define PERIOD                  0.5
 
/*  Compare strings
 */
#define STRCMP(s1,s2)           __builtin_strcmp(s1,s2)
 
 
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 );
 
  /*  Configure the counter to overflow every 0.001 s.
   *  The compare unit `compare0` is used to store the top value.  Unless
   *  otherwise stated, the overflow will occur at top in `up_loop` counting
   *  mode, at bottom in `updown_loop` counting mode.
   */
  hwa( configure, COUNTER,
       clock,     ioclk / CLKDIV,
       direction, COUNTMODE,
       bottom,    0,
       top,       compare0 );
  
  /*  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, compare0), (uint8_t)(0.5 + 0.001 * HW_SYSHZ / CLKDIV / 2) );
  else
    hwa( write, (COUNTER, compare0), (uint8_t)(0.5 + 0.001 * HW_SYSHZ / CLKDIV) );
 
  /*  Write this configuration into the hardware
   */
  hwa( commit );
 
  static uint8_t n ;
  for(;;) {
    if ( hw( read, (COUNTER,irq,overflow) ) ) {
      hw( clear, (COUNTER,irq,overflow) );
      n++ ;
      if ( n >= (uint8_t)(PERIOD / 2.0 / 0.001) ) {
        n = 0 ;
        hw( toggle, PIN_LED );
      }
    }
  }
}