hwa/atmel/avr/examples/10-1-acmp/main.c

Turn a LED on for 1 ms each time the analog comparator output toggles.

main.c

 
/*  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 analog comparator positive input
 *    This can be `bandgap` or `pin_ain0` (or synonym)
 */
#define REFERENCE               bandgap
 
/*  The analog comparator output edge that will trigger an IRQ
 *    This can be `falling`, `rising` or `both`
 */
#define EDGE                    falling
 
/*  The counter used to produce the LED pulse
 */
#define COUNTER                 counter0
#define COUNTER_CLK_DIV         64
#define COMPARE                 compare0
 
/*  The time the LED is turned on in seconds
 */
#define ON_TIME                 0.001
 
/*  The time the LED is turned on in counter units
 */
#define ON_TIME_COUNT           ON_TIME * HW_SYSHZ / COUNTER_CLK_DIV
 
 
/*  Service counter-compare0 IRQ:
 *    disable this IRQ
 *    turn the LED off
 *    turn analog comparator IRQ on
 */
HW_ISR( (COUNTER,COMPARE,irq) )
{
  hw( disable, (COUNTER,COMPARE,irq) );
  hw( write, PIN_LED, 0 );
  hw( clear, (acmp0,irq) );
  hw( enable, (acmp0,irq) );
}
 
 
/*  Service analog comparator interrupt:
 *    disable this IRQ off
 *    turn the LED on
 *    program a compare-match IRQ to occur in 1ms.
 *      (maybe reset the prescaler)
 */
HW_ISR( (acmp0,irq) )
{
  hw( disable, (acmp0,irq) );
  hw( write, PIN_LED, 1 );
 
  if ( COUNTER_CLK_DIV > 1 )
    hw( turn, (COUNTER,prescaler0), off );
 
  hw( write, COUNTER, 0 );
 
  if ( COUNTER_CLK_DIV > 1 )
    hw( turn, (COUNTER,prescaler0), on);
 
  hw( clear, (COUNTER,COMPARE,irq) );
  hw( enable, (COUNTER,COMPARE,irq) );
}
 
 
int main ( )
{
  /*  Create a HWA context to collect the hardware configuration
   *  Preload this context with RESET values
   */
  hwa( begin, reset );
 
  /*  Have the CPU enter idle mode when the 'sleep' instruction is executed.
   */
  hwa( configure,  core0,
       sleep,      enabled,
       sleep_mode, idle );
 
  /*  Configure LED pin
   */
  hwa( configure, PIN_LED, mode, digital_output );
 
  /*  If REFERENCE is a pin, configure it in analog mode (disable its digital
   *  input buffer)
   */
#if HW_ADDRESS(REFERENCE) != -1
  hwa( configure, REFERENCE,
       mode,      analog_input );
#endif
 
  /*  Configure INPUT_NEG pin in analog mode (disable digital input buffer)
   */
  hwa( configure, PIN_ANALOG_INPUT,
       mode,      analog_input );
 
  /*  Check that the counter can handle the ON_TIME value. This must be done
   *  here since the C preprocessor does not allow floats in expressions.
   */
  if ( ON_TIME_COUNT > ((1UL<<HW_BITS(COUNTER))-1) )
    HWA_E("COUNTER can not afford ON_TIME.") ;
 
  /*  Configure the counter to count from 0 to max
   */
  hwa( configure, COUNTER,
       clock,     ioclk / COUNTER_CLK_DIV,
       direction, up_loop );
 
  /*  Prepare the compare value for the PIN_LED pulse
   */
  hwa( write, (COUNTER,COMPARE), ON_TIME_COUNT );
 
  /*  Configure the analog comparator
   */
  hwa( configure,      acmp0,
       edge,           EDGE,
       positive_input, REFERENCE,
       negative_input, PIN_ANALOG_INPUT );
 
  hwa( enable, (acmp0,irq) );
 
  /*  Write this configuration into the hardware
   */
  hwa( commit );
 
  hw( enable, interrupts );
 
  for(;;)
    hw( wait, irq );
 
  return 0 ;
}