USB Hub Design

Started by jvoytovich October 3, 2008
Hi All,

I've got a project that I need advice on involving USB hubs. A
customer has a temperature controller with an RS232 interface that we
want to move to a USB design. The new interface will appear as a COM
port, so the host software will see no change. So far - so good.

An idea I had was to implement a second "port" on the controller so
that new host software could be added to provide a higher level
interface. For instance, the host could track the temperature and
display it on a graph, provide statistical summaries, etc. So as to
not conflict with the original software, this new functionality would
attach through a new COM port number.

I could add another USB port, but that would be really complicated in
that the data would have to be shared between 2 PICs to add 2 ports
(not to mention that 2 connectors, etc). More cost and complexity.

A brainstorm (or brain cramp) brought me to making the controller
appear as a USB hub, and therefore being able to add 2 logical USB
ports through 1 physical USB port. Has anyone had any direct
experience with USB hubs? If I can do this, it would be really cool. I
could then add maybe a 3rd port which would allow for direct
monitoring of the 1st port for debug purposes. Seems that the end
users of this device are always either dropping data or sending
illegal data and trying to blame it on our software. And of course
THAT never happens, does it??

Thanks for the replies.

Joe

> . So as to
> not conflict with the original software, this new functionality would
> attach through a new COM port number.

make HW appear as one virtual comport, use ''xport3'' to make that
appear as multiple ports, i have used this to share one GPS receiver
with several pieces of mapping software etc

FTDI makes the FT2232 Dual USB UART. If you uC has two serial ports,
you are in business.

http://www.ftdichip.com/FTProducts.htm#FT2232C

Richard

I've used the FTDI host controller chip in another project to add a
flash drive to a PIC board. On my current project though, it probably
wouldn't "fit". It would add more cost (chip and crystal), then force
me to use a different family (probably a 24F instead of an 18F). The
current 18F is also pretty well I/O bound, with only a few IO lines
open, so that also might make me go to a much larger chip. UGH! MESSY!

I'd also have to put in software to handle the FTDI chip. For a
"little" extra work, I can add the software directly to the 18F chip,
save gobs of hardware costs and be able to add as many new 232 ports
as I need.

Thanks anyway for the idea. I totally forgot that this option was
available!

Joe

--- In p..., "rtstofer" wrote:
>
> FTDI makes the FT2232 Dual USB UART. If you uC has two serial ports,
> you are in business.
>
> http://www.ftdichip.com/FTProducts.htm#FT2232C
>
> Richard
>