Pulse
            Width Modulated waveform using Timer/Counter0
             
          The bits of the two control registers TCCR0 and OCR0 are manipulated
          to generate the PWM. PB3 should be set as output by setting the
          corresponding bit in DDRB
        
          setReg(DDRB,
          8)      # set PB3 as output
          WGM01=3
          WGM00=6
          COM01=5
          setReg( TCCR0 , (1 << WGM01) | (1 << WGM00) | (1 <<
          COM01)  |  1)
          setReg(OCR0 ,  64)