31 Aug
2013
31 Aug
'13
7:05 p.m.
Gordon JC Pearce wrote:
According to the USB MIDI spec there is an event packet to send just
single bytes.
There are devices that do not support this single-byte packet.
On Sat, Aug 31, 2013 at 11:34:33AM +0200, Clemens
Ladisch wrote:
So the messages used by the CZ1000 in this protocol are not actually
MIDI messages.
Gordon JC Pearce wrote:
The CZ1000 expects seven bytes to start the sysex transfer, at which
point it will reply with a message and wait for an acknowledge. The
the PC should start to send the patch data, but it's quite important
not to send that too soon otherwise the CZ will misbehave in various
interesting ways. Once all the patch data is send - with breaks for
acks in between - the final 0xf7 is sent to terminate the sysex dump. 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. 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. This isn't implemented in the kernel,
It's used for real-time messages.
it would be incredibly handy for sysex transfers,
debugging and the
like.
Perhaps the answer is just to ditch alsa and poke the USB device with
libusb?
Or change the driver to always use single-byte packets (modify the first
"if" in snd_usbmidi_transmit_byte).
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.
In what way corrupted?
Regards,
Clemens