[LAD] Firewire bus analysis - Digidesign 003 Rack

[Damien Zammit]

Hi folks,

I have done some firewire bus analysis on the 003 Rack and posted last
year some of my findings on ffado.org wiki.
inter
Today I got back into it and managed to modify Clemens' snd-dice
driver to activate the 003R and made a standalone driver to play out
of 2 channels!
It's a non standard protocol, because you have to send particular
requests and wait for particular responses but I have documented as
much as I can.

Unfortunately during playback there are 2 outstanding issues:
1) There is extraneous low level noise when sound is routed through
channel 1 or channel 18 (first and last pcm channel). When sound is
routed into channel 1, noise is heard in channel 2 and channel 1
sounds normal.  When sound is routed into channel 18, similar noise is
heard in channel 1 but nothing else is heard.

2) I don't know why but the device spits out a request on the bus
about 10 times per second which interrupts playback for very short
intervals causing choppy playback.  I had a similar problem when
trying to make the 003R work under ffado.  I have examined the
behaviour of the device under windows and it does not generate these
packets.  Could it be the way the iso resources are being handled?  I
am allocating a tx and rx stream separately since without both, the
device stops transmitting in under 2 seconds, while with this driver,
it stays stable indefinitely.

I could use some advice on where to look next.

Damien