Bare metal programming with style

Blink a LED 10 times using the watchdog "IRQ or reset" mode.

FIXME: once the device goes into sleeping mode with , hardware reset does not awake it. Only a power-off/power-on cycle does wake it up.

/* 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
/* Watchdog timeout
#define TIMEOUT 250ms
/* Watchdog timeout interrupt
* The IRQ awakes the MCU but the ISR itself does nothing. We can spare a few
* bytes of program memory declaring the ISR 'naked' and inserting the 'reti'
* instruction ourselves (otherwise avr-gcc does some register
* initializations even though none is used).
HW_ISR( (watchdog0,irq), naked )
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 power_down mode when the 'sleep' instruction is
* executed and make it wake up as a watchdog interrupt occurs.
hwa( configure, core0,
sleep, enabled,
sleep_mode, power_down );
/* Go into sleep definitely if the watchdog triggered a reset.
if ( hw(stat,core0).reset_by_watchdog ) {
hwa( clear, core0 );
/* When the device is reset by the watchdog, the watchdog remains enabled
* so we must stop it.
hwa( disable, watchdog0 );
hwa( commit );
hw( wait, irq );
for (;;) /* This should */
hw( toggle, PIN_LED ); /* not happen */
/* Configure the watchdog to time-out every TIMEOUT (this will wake the CPU
* up), setting its flag the first time, resetting the device the second time
* if it has been reconfigured.
hwa( configure, watchdog0,
timeout, TIMEOUT,
action, irq_or_reset );
/* Write this configuration into the hardware
hwa( commit );
/* MCU can't awake from sleep without interrupts!
hw( enable, interrupts );
static uint8_t count ;
for(;;) {
hw( wait, irq );
/* When watchdog action is 'irq_or_reset', a timeout automatically disables
* the IRQ so that next timeout will reset the device. Load the context
* with this information, but do not write it into hardware.
hwa( disable, (watchdog0,irq) );
hwa( nocommit );
hw( toggle, PIN_LED );
count++ ;
if ( count < 19 ) {
* Re-enable the watchdog IRQ.
hwa( enable, (watchdog0,irq) );
hwa( commit );
#define hwa(...)
hwa( action, object [,...] ) stores an action for an object into a HWA context.
Definition: hwa_macros.h:552
#define hw(...)
hw( action, object [,...] ) executes an action immediately on an object.
Definition: hwa_macros.h:523
#define hw_asm(...)
Insert inline assembler code.
Definition: hwa_2.h:37
#define HW_ISR(...)
Definition: hwa_interrupts.h:80