Servotest

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

#define F_CPU 8000000L
#define baudrate 9600L
#define bauddivider (F_CPU/(16*baudrate)-1)
#define HI(x) ((x)>>8)
#define LO(x) ((x)& 0xFF)

#define LED1 4
#define LED2 5
#define LED_PORT PORTD
#define LED_DDR DDRD

#define PWM_OUT 3
#define PWM_DDR DDRB
#define PWM_PORT PORTB

#define TIMER_CLK_DIV64         0x03    ///< Timer clocked at F_CPU/64
#define TIMER_PRESCALE_MASK     0x07    ///< Timer Prescaler Bit-Mask

#define TIMER0_PRESCALER TIMER_CLK_DIV64
#define TIMER0_PRESCALER_VALUE (1<<(3*(TIMER0_PRESCALER-1)))

#define MIN_INTERVAL 1000 //microsecond
#define MAX_INTERVAL 2000 //microsecond
#define CLK_INTERVAL (1000000/(F_CPU/TIMER0_PRESCALER_VALUE)) //microseconds
#define MIN_CLKTIMER (MIN_INTERVAL/CLK_INTERVAL) //timer ticks
#define MAX_CLKTIMER (MAX_INTERVAL/CLK_INTERVAL) //timer ticks
#define MID_CLKTIMER ((MAX_CLKTIMER+MIN_CLKTIMER)/2)

#define BV(bit) (1<<(bit))
#define cbi(reg,bit) reg &= ~(BV(bit))
#define sbi(reg,bit) reg |= (BV(bit))
#define outb(addr, data) addr = (data)
#define inb(addr) (addr)

volatile unsigned char pwm;

void init(void)
{
    initUSART();
    initIO();
    initOC0();
}

void initIO(void)
{
    LED_DDR = 1<<LED1 | 1<<LED2;
}

void initUSART(void)
{
    UBRRL = LO(bauddivider);
    UBRRH = HI(bauddivider);
    UCSRA = 0;
    UCSRB = 1<<RXEN|1<<TXEN|1<<RXCIE|0<<TXCIE;
    UCSRC = 1<<URSEL|1<<UCSZ0|1<<UCSZ1;
}

void timer0SetPrescaler(unsigned char prescale)
{
    outb(TCCR0, (inb(TCCR0) & ~TIMER_PRESCALE_MASK) | prescale);
}

void initOC0(void)
{
    sbi(PWM_DDR, PWM_OUT);
    cbi(PWM_PORT, PWM_OUT);

    timer0SetPrescaler(TIMER0_PRESCALER); //start timer0 PWM

    sbi(TCCR0, WGM00);
    sbi(TCCR0, WGM01);

    cbi(TCCR0, COM00);
    sbi(TCCR0, COM01);

    pwm = MID_CLKTIMER;
    OCR0 = pwm;
}

ISR(USART_RXC_vect)
{
switch(UDR)
    {
    case '1': {
        sbi(LED_PORT, LED2);
        break;
        }
    case '0': {
        cbi(LED_PORT, LED2);
        break;
        }
    case 'q': {
        if (pwm<MAX_CLKTIMER-1)
            pwm += 1;
        else
            pwm = MAX_CLKTIMER;
        OCR0 = pwm;
        break;
        }
    case 'a': {
        if (pwm>MIN_CLKTIMER+1)
            pwm -= 1;
        else
            pwm = MIN_CLKTIMER;
        OCR0 = pwm;
        break;
        }

    case 'w': {
        if (pwm<MAX_CLKTIMER-10)
            pwm += 10;
        else
            pwm = MAX_CLKTIMER;
        OCR0 = pwm;
        break;
        }
    case 's': {
        if (pwm>MIN_CLKTIMER+10)
            pwm -= 10;
        else
            pwm = MIN_CLKTIMER;
        OCR0 = pwm;
        break;
        }
    case 'e': {
        pwm = MAX_CLKTIMER;
        OCR0 = pwm;
        break;
        }
    case 'd': {
        pwm = MIN_CLKTIMER;
        OCR0 = pwm;
        break;
        }
    case 'r': {
        pwm = MID_CLKTIMER;
        OCR0 = pwm;
        break;
        }
    default: {
        break;
        }
    }
}

int main(void)
{
    unsigned char i;
    unsigned char j;
    init();
    sei();

    while (1)
    {
        i++;
        if (i==64) {
            j++;
        }

        if (j>127) {
            sbi(LED_PORT, LED1);
        } else {
            cbi(LED_PORT, LED1);
        }
    }
}