1) The firmware looks for the presence of a CC LED and switches to CC mode automatically. This works fine on the prototype but in case it doesn't on other clocks, you can force it into CA or CC mode by holding down S1 or S2 at power-up, respectively

2) The interrupt-based PWM mode described in the article caused some flickering at low brightness setting. The final version of the code uses hardware PWM that eliminates this. It's possible to switch back to interrupt-based PWM by uncommenting the line "//#define INTERRUPT_BASED_PWM".

3) The LED test on power-up can be skipped by pressing S1.
