[LAU] MotU Ultralite AVB observations.

John Murphy rosegardener at freeode.co.uk
Sat Mar 7 13:28:26 CET 2020

Getting my Ultralite AVB working on Linux Mint 19.3 has been quite
a struggle and I've learnt a few things along the way, which may
save others some wondering.

Ignore any thoughts of USB power management causing any issue.
The device never uses any USB power, as confirmed with an inline
USB V/A meter.

Firmware more recent than 1.3.2+520 suffers from the 'bitcrusher'
effect, where audio can be heard for about 30 seconds, until it
fades to junk while appearing on higher number channels, until
it does the same again. That firmware is pre Touch Consoleā„¢.

Firmware and release notes in the Ultralite AVB section here:

A great deal of good information over at the Linux Musicians forum:
(Thanks to Eric Schoster for pointing me to that one.)

One gem is that it can be set to class compliant mode with:
curl --data 'json={"value":"UAC"}' IP address/datastore/host/mode
curl --data 'json={"value":"24"}' IP address/datastore/host/maxUSBToHost

(Replace "IP address" with its address on your network)

Change to its proprietary mode with:
curl --data 'json={"value":"USB2"}' IP address/datastore/host/mode
curl --data 'json={"value":"64"}' IP address/datastore/host/maxUSBToHost

On my current hardware (i7-8700K) the Ultralite takes 27 seconds
from first light in the display to showing detail in the display
and there's a further 20 second delay before any activity shows
up in a terminal window running 'tail -f /var/log/syslog'.

There are very many messages like:

'clock source 1 is not valid, cannot use'

Yesterday I was seeing 240 of those in blocks of 40, with each
block followed by:
'[pulseaudio] module-alsa-card.c: Failed to find a working profile.'
and etc.

Today, after trying the latest firmware, seeing the bitcrusher
effect and reverting to 1.3.2+520 again, I only see two complete
blocks and the reporting stops about half way through the third
block. Qjackctl will then start the server, on either hw:AVB or
hw:AVB,0. It always seems to need changing to the one of those
it isn't set to. :)

I can only think that my dual booting and using it on Windows 10
caused the trouble I was seeing when using it on Linux afterwards.

I still can't use anything which isn't 'jack aware', but I can
live with that, for now. VLC offers 13 'Ultralite AVB, USB Audio'
devices to chose from, including "Direct sample snooping device".

Linux, generally, doesn't seem to maintain an optical output if
a player app stops playing...


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