Joe Giacobello skrev:
Peter, many thanks for your tip regarding hot plugging and that seems
to have been my problem here. I'm curious to know just exactly what
you mean by hot plugging. Should one not disconnect the serial plug
while data are flowing or when any electrically active sending or
receiving device is connected? In other words, should all the units
in such a system be "off"?
Frankly, I have been using and working with computers since the days
of the Vic 20 and I wasn't aware of the sensitivity of UARTs to that
kind of failure. Apparently, it's a well known problem.
73, Joe
K2XX
Hi Joe,
Hot plugging is simply the practice of plugging or un-plugging the cable
while the connected devices are powered up.
In this case the DB-25/DB-9 connectors have not been designed to have
guarantied GND connection established before any other pins have a
chance of connecting with their counterpart. Couple that with the common
practice of running computers and other electronic gear without a
safety-ground connection (against all recommendations or even
requirements for installation), is begging for trouble. All computer
power-supplies have filters in their mains input, employing a capacitive
potential divider between the phase and return, with the midpoint tied
to ground. If the ground is allowed to float, or just have a rather high
resistance to ground, there may be as much as a 115V (with 230V mains)
AC ground potential on the device. Connecting such a device to other
electronic devices, with other ground potential, is clearly a recipe for
failures.
--
Vy 73 de OZ1PIF/5Q2M, Peter
** CW: Who? Me? You must be joking!! **
email: peter(no-spam-filler)@frenning.dk
http://www.frenning.dk/oz1pif.htm
Ph. +45 4619 3239
Snailmail:
Peter Frenning
Ternevej 23
DK-4130 Viby Sj.
Denmark
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