[LAD] Weird USB MIDI sysex problem

Gordon JC Pearce gordonjcp at gjcp.net
Sat Aug 31 11:45:08 UTC 2013

On Fri, Aug 30, 2013 at 11:35:59PM +0100, Gordon JC Pearce wrote:
> Hi folks,
> 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 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.

With a bit of testing, I've determined that at least the USB interfaces I have at hand do not support sysex.  They will pass some interestingly "interpreted" version of sysex, which is of course corrupted and unreadable by the device.  This pretty much explains why I've never successfully transferred anything over sysex.

Looks like I need to devise an interface that doesn't use USB-MIDI for sysex.

Gordonjcp MM0YEQ

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