main.c


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#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include "uart.h"

#define SET_PWM(a) (OCR0A  = (a))

void setup(void);

int main(void)
{
    uint8_t output = 0, c;

    setup();

    for (;;) {
        switch((c = uart_getchar())) {
            case '?': break;
            case 'n':
            case '0': output  = 0; break;
            case 'y':
            case '1': output  = 1; break;
            case 't':
            case 'T': output ^= 1; break;
        }

        uart_putchar(c);

        if (output)
            SET_PWM(40);
        else
            SET_PWM(1);

        _delay_ms(1000);
        SET_PWM(0);
    }

    return 0;
}

void setup(void)
{
    /* serial */
    uart_init();

    /* Initialize timer for PWM
     *** PWM with timer1 management:
     * TCCR1A-COM1A1:
     * TCCR1A-WGM10:
     * TOP = 0x00FF
     * frequency is : 12 MHz(fclk) / 256(prscl) / 255 (top)/ 2 = 91.91Hz
     * frequency is : 18.432 MHz(fclk) / 256(prscl) / 255 (top)/ 2 = 141.18Hz
     * frequency is : 18.432 MHz(fclk) / 1024(prscl) / 255 (top)/ 2 = 35.29Hz
     * frequency is : 16 MHz(fclk) / 1024(prscl) / 255 (top)/ 2 = 30.64Hz
     * TCCR1B CS12 = 256 prescaler, CS12 + CS10 = 1024 prescaler
     *
     * 23/24 =~ 1.5ms
     */
    TCCR0A |= _BV(COM1A1)  | _BV(WGM10);
    TCCR0B |= _BV(CS12)    | _BV(CS10);
    /* TIMSK0 |= _BV(TOIE0); */

    /* pwm output; */
    DDRD |= 0xFF;
}