[Beowulf] Re: multiport RS232 to ethernet (or USB) (Jim Lux)

David Mathog mathog at caltech.edu
Fri Apr 7 19:06:01 EDT 2006


On Thu, 06 Apr 2006 15:50:34 -0700
Jim Lux wrote:

> 
> Except that the piece of hardware the serial port is talking to uses RTS 
> and CTS, not as handshaking lines, but to wake up the box, and to return 
> status.

In that case be very careful about bit states on power
transitions affecting the USB hub and the controlling computer.
I had all sorts of fun controlling some TrippLite UPS's that
used a similar "bit level" serial line control methodology.
Some computers would come up with the serial port lines
bouncing around at random, which could send an "inverter kill"
signal to the UPS at just the wrong time.

You may well find that when you reboot the master machiine all
hell breaks loose on the USB->serial controlled slave devices.

Regards,

David Mathog
mathog at caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech
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