[sdiy] Handling MIDI Running Status from Power-up

Neil Johnson neil.johnson71 at gmail.com
Fri Nov 15 10:47:55 CET 2019


Didrik Madheden wrote:
> On Thu, 14 Nov 2019 at 19:43, Next Expanse <nextexpanse at gmail.com> wrote:
> > The right way to solve this would be to have a bidirectional protocol, some sort of way for the receiver to detect when it’s been disconnected, and to have a way for the module to query the controller’s state. Nothing else will fix the problem, so unless there are some serious changes, we have to live with it.
> The issue could be mitigated somewhat by some cleverness on both the
> sending and receiving side.

The MIDI spec (from 1996) says:


Use of Active Sensing is optional for either receivers or
transmitters. This byte (FE) is sent every 300 ms
(maximum) whenever there is no other MIDI data being transmitted. If a
device never receives Active
Sensing it should operate normally. However, once the receiver
recognizes Active Sensing (FE), it then
will expect to get a message of some kind every 300 milliseconds. If
no messages are received within this
time period the receiver will assume the MIDI cable has been
disconnected for some reason and should
turn off all voices and return to normal operation. It is recommended
that transmitters transmit Active
Sensing within 270ms and receivers judge at over 330ms leaving a
margin of roughly 10%."


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