[LAD] Weird USB MIDI sysex problem

Clemens Ladisch clemens at ladisch.de
Sat Aug 31 09:34:33 UTC 2013

Gordon JC Pearce wrote:
> I'm having some really odd behaviour trying to send sysex to a synth
> where I can only send (using snd_rawmidi_write) in three-byte blocks.

The USB MIDI protocol happens to send SysEx data in groups of three
bytes, but this does not need to concern you because any remaining bytes
are flushed at the end of each message.

> The only exception is if I send something not a multiple of three
> bytes but terminate the transfer with 0xf7, it will send
> everything including the 0xf7 - but this kills the sysex transfer.

_Every_ SysEx message must be terminated with F7.

What do you mean with "kills"?

> Is it really impossible to just send raw bytes over a USB MIDI cable?

It is possible to send MIDI messages over a USB MIDI cable.


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