[time-nuts] RE : Re: FASTRAX GPS
jl.oneto at free.fr
Wed Jul 2 16:29:14 EDT 2014
AFAIK, the differential variant of RS-232 is RS-485. I'm not sure about the levels.
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-------- Message d'origine --------
De : Chris Albertson <albertson.chris at gmail.com>
Date :02/07/2014 21:36 (GMT+01:00)
A : Discussion of precise time and frequency measurement <time-nuts at febo.com>
Objet : Re: [time-nuts] FASTRAX GPS
I tried using it as pairs but you really can't. You have Tx, Rx and
the PPS all sharing one ground return and the ground is not even a
current return because each end is connected tho the building ground
system. So you can TRY to use pairs like I did but it remains
Yes you can make it work by using balanced pairs but then it is no
longer RS232 and need driver/receiver chips and level conversion at
each end. Balanced lines work very well.
The problem is that the RS232 receiver looks only at the voltage on
one of the wires in the pair relative to ground and not the difference
between the wires in the pair.
On Wed, Jul 2, 2014 at 10:45 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
> albertson.chris at gmail.com said:
>> I tried using a long serial cable. Just because I had some 100 feet of
>> cat-5 wire already installed. It did not work reliably I was using a MAX232
>> chip as a driver.
> Were you using it as 8 separate wires or 4 pairs?
> I'd expect RS-232 to work over 100 ft of Cat-5 if you used half of each pair
> as a ground. (That's at 9600 baud.)
> These are my opinions. I hate spam.
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