Tone limit 20KHz

[Tech-TX]

Add 2 comments since I found out where the 5KHz upper limit on Tone output frequency was, apparently added for compatibility with the Arduino library some time in the past.

If you want the full 20KHz audio frequency range, change the two lines in Tone.cpp at line 38 to:

  high = std::max(high, (uint32_t)25);  // new 20KHz maximum Tone frequency
  low = std::max(low, (uint32_t)25);

[earlephilhower]

Thanks for the add'l comment, but I can see no reason not to extend the range by default to 20kHz like you were mentioning.

[Tech-TX]

Done, and done! I'll good with removing artificial restraints on operation. 😄
Travis CI running now.

[Tech-TX]

FYI, I've already tested this change yesterday much farther than 20KHz. When I tried to take it to 65535 it blew up, but I sort of expected that based on your notes elsewhere about CPU utilization at 40KHz PWM.

[earlephilhower]

Thx!