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RE: [avr-gcc-list] AVR with USB

From: Scott and Roxanne Munns
Subject: RE: [avr-gcc-list] AVR with USB
Date: Thu, 14 Nov 2002 22:24:44 -0600


This is my first post to the list, though I've been lurking for some time.
Finally a question I can sink my teeth into!

As I'm sure you're aware, RS485 vs. USB depends on your cost, latency, and
bandwidth needs.  Another important factor is the bus length you need.
RS485 can be stretched out for thousands of feet if you need it.  Using
RS485 with a PC will require either a custom serial card and driver or an
auto-enabled RS232-RS485 converter (around $60 for a good one from B&B

For my day job, we have produced thousands of AVR devices for a distributed
control system just as you described.  Most are 4433s (switching to Mega8)
or Mega128s.  We chose a token bus protocol so every node is guaranteed a
chance to talk.  You may be able to do much better on latency and bandwidth
if you only have a single PC master and poll all of your slaves for data.

I'm not sure what the cost for the USB device is, but we've been very
pleased with implementing our protocol with RS485, and it's cheap.

Best wishes,
Scott Munns

-----Original Message-----
From: address@hidden [mailto:address@hidden
Behalf Of Tom Harris
Sent: Thursday, November 14, 2002 6:42 PM
To: address@hidden
Subject: [avr-gcc-list] AVR with USB


Has anyone used (or even seen) one of the AVR parts with an embedded USB
hub? The part code is AT43USB355. We are thinking of using them as the
slaves for a distributed control system hosted by a PC. The bandwidth
requirements are not excessive, I am wondering if it is not overkill and a
RS485 network with some dynamic addressing scheme bolted on might not be a
better idea, then we could use more standard AVRs.

Tom HArris <tomh(AT)optiscan(DOT)com>

avr-gcc-list at http://avr1.org

avr-gcc-list at http://avr1.org

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