hwa/atmel/avr/examples/03-2-blink-counter-compare-flag/main.c

Blink a LED using a counter compare-match flag

 
/*  This file is part of the HWA project.
 *  Copyright (c) 2012,2015 Christophe Duparquet.
 *  All rights reserved. Read LICENSE.TXT for details.
 */
 
/*  Set a default target board
 */
#include BOARD_H
 
 
/*  The counter
 */
#define COUNTER                 counter0
#define CLKDIV                  64
#define COMPARE                 compare0
#define PERIOD                  0.5
 
 
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 count from 0 to its max and loop
   */
  hwa( configure, COUNTER,
       clock,     ioclk / CLKDIV,
       direction, up_loop,
       bottom,    0,
       top,       max );
 
  /*  Configure the compare unit to match when 0.001 s has elapsed
   */
  hwa( write, (COUNTER,COMPARE), 0.001 * HW_SYSHZ / CLKDIV );
 
  /*  Write this configuration into the hardware
   */
  hwa( commit );
 
  static uint8_t n ;
  for(;;) {
    /*
     *  When a compare-match occurs, clear the counter, clear the flag and count
     *  the elapsed millisecond
     */
    if ( hw( read, (COUNTER,COMPARE,irq) ) ) {
      hw( write, COUNTER, 0 );
      hw( clear, (COUNTER,COMPARE,irq) );
      n++ ;
      if ( n >= (uint8_t)(0.5 + 1.0*PERIOD/0.001/2.0+0.5) ) {
        /*
         *  Toggle the LED when a half period has elapsed
         */
        n = 0 ;
        hw( toggle, PIN_LED );
      }
    }
  }
}