/*
 * ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * <address@hidden> wrote this file.  As long as you retain this notice you
 * can do whatever you want with this stuff. If we meet some day, and you think
 * this stuff is worth it, you can buy me a beer in return.        Joerg Wunsch
 * ----------------------------------------------------------------------------
 *
 * Bargraph demo.
 *
 * Infinitely converts the value on ADC0, and outputs a LED bargraph
 * on port B.  The ADC is used in free-running mode, and the LED port
 * is updated within the ADC ISR.
 *
 * $Id$
 */

#include <inttypes.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>

#if defined(__AVR_ATtiny26__)
#  define ADCINIT() ADCSR = _BV(ADEN) | _BV(ADSC) | _BV(ADFR) | _BV(ADIE)
#elif defined(__AVR_ATtiny261__) || defined(__AVR_ATtiny461__) \
	|| defined(__AVR_ATtiny861__)
#  define ADCINIT() ADCSRA = _BV(ADEN) | _BV(ADSC) | _BV(ADATE) | _BV(ADIE)
#else
#  error "Unknown MCU type."
#endif

ISR (ADC_vect)
{
    uint8_t adc, i;

    adc = ADCH;
    adc &= 0xE0;

    for (i = 0; adc != 0; adc -= 0x20)
	i = (i << 1) | 1;
    PORTB = ~i;
}

void
ioinit (void)
{
    /* Make port B all outputs, to drive the LEDs. */
    DDRB = 0xFF;
    /* Turn all LEDs off -- they are low-active. */
    PORTB = 0xFF;

    /* Set up the ADC. */
    ADMUX = _BV(ADLAR);
    ADCINIT();
    sei();
}

int
main (void)
{

    ioinit ();

    /* loop forever, the interrupts are doing the rest */

    for (;;)
        sleep_mode();

    return (0);
}