[sdiy] Is MIDI Active Sense necessary?

Colin f colin at colinfraser.com
Tue Feb 12 15:26:13 CET 2013

> All of my MIDI controllers filter out active sensing messages.

I ignore it too. It's more trouble than it's worth IMO.
The only thing it will do for you is kill hung notes if a MIDI cable gets
It's no help if you simply have an error in a note number that means the
note off gets missed.
Active sense also caused me about the most baffling bug I ever saw.
There was a hardware fault in a PIC about 10 years ago, that meant the first
read of the USART rxreg after a new byte was received was valid, but
subsequent reads would return the byte *before*.
It was down to some fault in the double-buffer design.
I might have realised what was happening a lot sooner, if active sense bytes
from my master keyboard hadn't been pushing bytes through 300ms after I was
expecting them.
The result was a MIDI to CV convertor that was putting 300ms MIDI delay on
every note on and off, for no apparent reason.

Colin f

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