Summary: when calling analogWrite() with values 0 or 255, it defaults to
analogWrite() which leaves PWM registers in the previous state, and the next
analogWrite() starts with a "glitch", very noticeable if "previous" and "next"
values are far apart.
A simple reproductible test case, with expected output and observed results, is
available on http://forum.arduino.cc/index.php?topic=303922.0
A simple solution is to get rid of the code that defaults to digitalWrite when
value == 0 or 255, but probably a cleaner solution would be to make sure that
registers are not influenced by the previous value upon starting PWM
This is on ATTiny85 using arduino-tiny cores 1.5 (with changed compiler path)
on Arduino 1.6 IDE
Original issue reported on code.google.com by
vicnevicneon 1 Mar 2015 at 10:26