ForumsHardware ← AxoCube : featuring 'standalone' soundplane

Im working on a project that will hopefully see the Soundplane 'untethered' from the computer :)

Im going to be posting images/updates etc over at the axoloti forum, as this will provide the synth engine, but I think Soundplane connectivity will be interesting to those here:

AxoCube project

basic details so far are:

  • Soundplane and Eigenharps controlled via a BeagleBone Black (recently changed!)
  • 4 Axoloti boards for virtual modular synth voices, fx, and sequencers
  • Ableton push for 'configuration' , sequencing UI etc
  • STM32F7Disco board - touch sensitive UI , for control when Push not connected, patch loading etc.

(it may be I eventually move the Soundplane/Eigenharp 'drivers' to the STM32 boards)

Beaglebone black is using the libusb drivers for the Soundplane developed by Per Eckerdal , Eigenharp libusb driver i put together, and a new app that will utilise Randy's Touch Tracker code.

Early days, but its looking promising...

more news/updates on the above thread.... and I guess I'll cross post a demo once things are developed a little further :)

Really cool project!

Sorry for the detailed questions, but do the USB Multi-Transaction Translator hubs add any latency when performing their feature? Seems like it would be unavoidable, although High Speed frame latency is only 1/8th Full Speed latency. Hopefully the total latency is only 1 ms + 0.125 ms = 1.125 ms.

Meanwhile, I assume that your STM32F7 Discovery Kit firmware must implement High Speed USB, otherwise the Multi-TT hub would not really provide any advantage when connected there.

STM32F7 (and Axoloti) has both FS and HS support.

the advantage of using a hub, is not only being able to connect multiple devices, is that I'm using it as a single power source... which is not only convenient but also will help when I add a USB batter pack to power the whole thing :)
I guess later, I might put in a power rail, but for now this make its easy to get on with the software side :)

it should be noted, the PI2 and Axoloti's can deliver 500mA to USB devices, so its feasible to use these without a hub with the soundplane, however the BBB, can only deliver 100mA so currently you need a powered hub for use with soundplane

(Id need to check the STM32F7 disco, for what it can supply as a USB host)

(I wonder if there is a device, thats a straight thru USB-USB, but can add external power? this might alleviate the need for the hub in some scenarios!)

Im also assuming that once the soundplane software is on-board that will pretty much max out a CPU/board. (perhaps excluding PI2) ... so you need another USB (or midi din) to get the data to another device... so devices with only one usb port will need a hub for that purpose

MTT, well every (2.0/3.0) hub has a translator in it to do 2.0 to 1.x... the MTT just has one per port, important IF you connect multiple 1.x devices.

does a translator create latency... I don't think any more than any hub will...
Im pretty sure they are 'protocol' aware, so the translation function is not used HS to HS,
only HS to FS.
Id have thought (may be wrong though) the latency is 0.125 (due to HS leg), e.g.:

w/o hub computer < 1.0ms FS < device

w/ hub computer < 0.125 HS < hub < 1.0ms FS < device

but honestly, id need to read the USB hub specification to see if this is true.

But, in practice Ive used my Eigenharp Alpha (HS) for quite some time through a MTT hub , and never noticed any latency difference to plugging it directly into the Mac. so technically perhaps some increase, but I've never felt it.
(and since last year, put the soundplane in the same hub, and also not noticed any extra latency)

but perhaps because the latency is 'constant' we just cope, we are generally very good at dealing with constant delays... its more jitter we 'feel'

Yes, constant latency is more easily ignored than jitter.

I was concerned about FS because the Soundplane is FS. So, it seems like the MTT would be forced to add latency.