Re: Multiple USB 1.1 devices in USB 2 Hub speed ?

On Wed, 16 Jul 2008 21:18:30 +0100, "Peter Dickerson"
<firstname.lastname@xxxxxxxxxxxxxxxx> wrote:

"Adrian" <adrianbica@xxxxxxxxx> wrote in message
news:c11ebd15-e7d7-4b6c-9a72-fac71de01b70@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Jul 16, 12:07 pm, Anton Erasmus <nob...@xxxxxxxxxxxxxxxx> wrote:
Hi,

If I have a number of USB 1.1 devices plugged into a USB 2 Hub, can I
get the full 12MB/s of each USB 1.1 device via the USB 2 link to a
host ? Or does the USB 2 link fall back to a 1.1 compatible mode ?


Not sure what's your question, it is a bit confusing. The two
statements around the OR are equivalent.

Briefly:
High speed = 480 Mbps (USB 2.0)
Full Speed = 12Mbps (USB 1.1)
Low Speed = 1.5Mbps (USB 1.1)
USB 2.0 is backward compatible, so is the hub. It should support a mix
of devices.

So, yes, you get the 12Mbps full speed AND yes, the USB 2 link falls
back to 1.1.

And No, you don't get the 12 MB/s for each device. You still get 12 MB/s to
share.

Thanks, this what I needed to know. So if I need to combine 6 full
speed devices into one High speed channel, I would need something with
6 1.1 host ports and one 2.0 device port. Are there any chipsets
available that does this kind of thing? I have six USB 1.1 devices
(FTDI chips in FIFO mode) each needing to send data at 3 Mbps to
a host PC. The PC has 6 USB ports, but I need to take these through a
sealed bulkhead, and the connectors I can get is to big to fit 6 of
them. So I either need to get smaller IP-67 sealed USB connectors, or
a way to combine the data into a single channel. I might be able to
fit 2 USB connectors in which case the Full Speed limit per channel
should be OK.

Regards
Anton Erasmus

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