SimplePwmFrequency.h

void setPwmFrequency(int pin, int divisor)
{
    byte mode;

    if (pin == 5 || pin == 6 || pin == 9 || pin == 10) {
        switch (divisor) {
            case 1: mode = 0x01; break;
            case 8: mode = 0x02; break;
            case 64: mode = 0x03; break;
            case 256: mode = 0x04; break;
            case 1024: mode = 0x05; break;
            default: return;
        }

        if (pin == 5 || pin == 6) {
            TCCR0B = TCCR0B & 0b11111000 | mode;
        } else {
            TCCR1B = TCCR1B & 0b11111000 | mode;
        }

    } else if (pin == 3 || pin == 11) {
        switch(divisor) {
            case 1: mode = 0x01; break;
            case 8: mode = 0x02; break;
            case 32: mode = 0x03; break;
            case 64: mode = 0x04; break;
            case 128: mode = 0x05; break;
            case 256: mode = 0x06; break;
            case 1024: mode = 0x7; break;
            default: return;
        }

        TCCR2B = TCCR2B & 0b11111000 | mode;
    }
}