PRR&=~(1<<PRTIM2); // write power reduction register to zero
    TIMSK2=(1<<OCIE2A); // compare match on OCR2A
    TCNT2=0;  // init counter
    OCR2A=29; // value to compare against
    TCCR2A=(1<<WGM21)|(0<<WGM20); // do not change any output pin, clear at compare match
    TCCR2B=(0<<WGM22)|(1<<CS22)|(1<<CS21)|(1<<CS20); // clock divider, start counter