void setup() { // Set the main system clock to 8 MHz. noInterrupts(); CLKPR = _BV(CLKPCE); // enable change of the clock prescaler CLKPR = _BV(CLKPS0); // divide frequency by 2 interrupts();

// Configure Timer 0 for phase correct PWM @ 25 kHz.
TCCR0A = 0;           // undo the configuration done by...
TCCR0B = 0;           // ...the Arduino core library
TCNT0  = 0;           // reset timer
TCCR0A = _BV(COM0B1)  // non-inverted PWM on ch. B
    | _BV(WGM00);  // mode 5: ph. correct PWM, TOP = OCR0A
TCCR0B = _BV(WGM02)   // ditto
    | _BV(CS00);   // prescaler = 1
OCR0A  = 160;         // TOP = 160

// Same for Timer 1.
TCCR1A = 0;
TCCR1B = 0;
TCNT1  = 0;
TCCR1A = _BV(COM1A1)  // non-inverted PWM on ch. A
    | _BV(COM1B1)  // same on ch. B
    | _BV(WGM11);  // mode 10: ph. correct PWM, TOP = ICR1
TCCR1B = _BV(WGM13)   // ditto
    | _BV(CS10);   // prescaler = 1
ICR1   = 160;

// Same for Timer 2.
TCCR2A = 0;
TCCR2B = 0;
TCNT2  = 0;
TCCR2A = _BV(COM2B1)  // non-inverted PWM on ch. B
    | _BV(WGM20);  // mode 5: ph. correct PWM, TOP = OCR2A
TCCR2B = _BV(WGM22)   // ditto
    | _BV(CS20);   // prescaler = 1
OCR2A  = 160;

}

void loop() { analogWrite( 3, 1); // duty cycle = 1/160 analogWrite( 5, 53); // ~ 1/3 analogWrite( 9, 107); // ~ 2/3 analogWrite(10, 159); // 159/160 }

void setup()
{
    // Set the main system clock to 8 MHz.
    noInterrupts();
    CLKPR = _BV(CLKPCE);  // enable change of the clock prescaler
    CLKPR = _BV(CLKPS0);  // divide frequency by 2
    interrupts();

    // Configure Timer 0 for phase correct PWM @ 25 kHz.
    TCCR0A = 0;           // undo the configuration done by...
    TCCR0B = 0;           // ...the Arduino core library
    TCNT0  = 0;           // reset timer
    TCCR0A = _BV(COM0B1)  // non-inverted PWM on ch. B
        | _BV(WGM00);  // mode 5: ph. correct PWM, TOP = OCR0A
    TCCR0B = _BV(WGM02)   // ditto
        | _BV(CS00);   // prescaler = 1
    OCR0A  = 160;         // TOP = 160

    // Same for Timer 1.
    TCCR1A = 0;
    TCCR1B = 0;
    TCNT1  = 0;
    TCCR1A = _BV(COM1A1)  // non-inverted PWM on ch. A
        | _BV(COM1B1)  // same on ch. B
        | _BV(WGM11);  // mode 10: ph. correct PWM, TOP = ICR1
    TCCR1B = _BV(WGM13)   // ditto
        | _BV(CS10);   // prescaler = 1
    ICR1   = 160;

    // Same for Timer 2.
    TCCR2A = 0;
    TCCR2B = 0;
    TCNT2  = 0;
    TCCR2A = _BV(COM2B1)  // non-inverted PWM on ch. B
        | _BV(WGM20);  // mode 5: ph. correct PWM, TOP = OCR2A
    TCCR2B = _BV(WGM22)   // ditto
        | _BV(CS20);   // prescaler = 1
    OCR2A  = 160;
}

void loop()
{
    analogWrite( 3,   1);  // duty cycle = 1/160
    analogWrite( 5,  53);  // ~ 1/3
    analogWrite( 9, 107);  // ~ 2/3
    analogWrite(10, 159);  // 159/160
}