[alsa-devel] Audigy bay protocol

Tony "Chainsaw" Vroon chainsaw at gentoo.org
Thu Jun 26 15:11:55 CEST 2008

Good afternoon,

Having spent some time looking at the MIDI that the internal/external
Audigy bays emit, I noticed that they report more then is currently used
by the LIRC driver.

There is one thing missing in here, which is how to control the bay
power LED (which is supposed to blink when the card is muted) and the
CMSS LED. I am not sure whether this is controlled through MIDI SysEx
sequences or through other means.

Due to an annoying hardware failure in my Audigy 4 Pro I can not
continue this endeavour, but I want to share what I have.

Based on this, perhaps one can extend the EMU10K1/2 driver a bit with
headphone muting and volume control through the bay. With thanks to the
libdouze author, Arnaud de Bossoreille de Ribou.

Midi System Exclusive ( extended manufacturer id == 0x2021 )
Payload for 61 bay message:
61 00 01 00 XX YY

00 = button push event
01 = volume knob event
02 = jack sense event

For XX=00 button push:
Bit 1: CMSS
Bit 2: Mute

For XX=01 volume knob:
Bit 1: Always set
Bit 7: Set for downward adjustment, unset for upward adjustment

For XX=02 jack sense:
YY contains jacks
Bit 1: headphone
Bit 2: digital out (back of bay)

Response to initialization:
Midi System Exclusive ( extended manufacturer id == 0x2021, payload == |
60 00 02 03 | )       <-- Unknown, bay version?
Midi System Exclusive ( extended manufacturer id == 0x2021, payload == |
61 00 01 00 02 01 | ) <-- Jack sense update

I hope it is of use to someone.

Tony V.
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