USB as a control network?

Anyone ever considered using USB as a (simple) control network instead 
of using something like CAN?

The USB master could be a small computer, maybe running Linux. The 
devices to be controlled could be based on the PIC18F2450 USB 
Microcontroller.

Bad idea?

Rob Horton wrote:

> Anyone ever considered using USB as a (simple) control network instead 
> of using something like CAN?
> 
> The USB master could be a small computer, maybe running Linux. The 
> devices to be controlled could be based on the PIC18F2450 USB 
> Microcontroller.
> 
> Bad idea?

AFAIK the rocketry club at Portland State University is planning just 
that.  You would have to manage your network closely to achieve any high 
level of determinism, but from my small knowledge of USB it could be done.

All in all I think using CAN would be safer, and in the end easier than 
trying to wedge USB into an application that it wasn't intended for.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google?  See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

Rob Horton wrote:
> Anyone ever considered using USB as a (simple) control network instead
> of using something like CAN?
>
> The USB master could be a small computer, maybe running Linux. The
> devices to be controlled could be based on the PIC18F2450 USB
> Microcontroller.
> 
> Bad idea?

Can you live with the short cable lengths (5m)?

Rob Horton <yahoo@mr_horton.com> wrote:
> Anyone ever considered using USB as a (simple) control network instead 
> of using something like CAN?

Probably some people started considering it.  But I bet most stopped
the moment they realized that USB isn't really a network, by any
stretch of the meaning of that word.  And that's before you consider
that the necessary hubs alone will can easily waste more power than
the entire collection of devices you wanted to control.

-- 
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.