HWA
Bare metal programming with style
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 ;
}
HW_BITS
#define HW_BITS(...)
Definition: hwa_1.h:495
hwa
#define hwa(...)
hwa( action, object [,...] ) stores an action for an object into a HWA context.
Definition: hwa_macros.h:552
HWA_E
#define HWA_E(...)
Trigger an error after code optimization.
Definition: hwa_2.h:17
hw
#define hw(...)
hw( action, object [,...] ) executes an action immediately on an object.
Definition: hwa_macros.h:523
PIN_ANALOG_INPUT
#define PIN_ANALOG_INPUT
Definition: attiny84.h:98
HW_ISR
#define HW_ISR(...)
Definition: hwa_interrupts.h:80