On Wednesday, 4 January 2017 16:36:54 GMT William R Sowerbutts wrote:
> >Well OK. I am surmising that there are conflicts when the three devices
> >are all shouting.
>
> It may be that there isn't enough USB bandwidth to serve multiple low-speed
> isochronous devices concurrently.
That is what I think too. If the V1.1 devices throttle the hub to 12 Mps (see
below), then
there could well be an issue.
> You might try using a multi transaction translator ("Multi-TT") hub instead.
>
> https://en.wikipedia.org/wiki/USB_hub#Transaction_translator
> http://www.tomshardware.com/reviews/usb-technology,677-3.html
>
> "lsusb -v" will tell you if your hardware supports multi-TT
> (bInterfaceProtocol, 1 = single-TT, 2 = multi-TT) and if it is enabled
> (bDeviceProtocol, again 2 = multi-TT).
>
> Although even if multi-TT works, maintenance could be a problem; the risk
> would be that one day the hub breaks, someone replaces it with a Single-TT
> hub assuming it is equivalent to the failed hub, and the thing mysteriously
> breaks.
It's probably cheaper to buy a Pi 3 :-)
The hub that I borrowed from David Wilkinson was USB 2.0 and so is the Naked
one that
we are using for the project, so they should have had at least one built-in
transaction
translator according to Toms hardware.
--
Terry Coles
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