[time-nuts] GPS and other low speed data via CAT5 wire

Bob Burchett bob.burchett at eeontheweb.com
Wed Jul 2 23:24:20 UTC 2014


I have run 9600 baud data over 200-300' many times and the statement that a
RS232 driver is being used (presumably a Max-232 which is pretty popular &
the one we use) then it will drive a couple of hundred feet of wire BUT
there is one catch we learned early-on. That is to double up the wires to
lower the resistance and since CAT5 has 4 pairs you only need TX, RX and Gnd
of course; so if you use one pair for each line that even leaves one pair
left over and we have seen up to 300' of line driven by this trick. 

Naturally it is something of a pain to put 2 wires in a crimp-on pin to get
them into a DB9 or whatever connector you are using...that is a given, but
the end does justify the means sometimes. 

I sure wouldn't try it at 19,200 or above of course; but for 9600 or lower
(perhaps switch to 4800 if you can do it...) we have a 100% success rate. 

Perhaps this will help...

Robert L. (Bob) Burchett
Certified Communications Engineer
Enterprise Electronics
Contractors License 522372
22826 Mariposa Ave. 
Torrance CA 90502
310.534.4456
Bob.Burchett at EEonTheWeb.com


-----Original Message-----
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Today's Topics:

   1. Re: FASTRAX GPS (Chris Albertson)
   2. Re: FASTRAX GPS (Alexander Pummer)
   3. Re: FASTRAX GPS (Chris Albertson)
   4. RE : Re:  FASTRAX GPS (Jean-Louis Oneto)
   5. Re: FASTRAX GPS (jim s)
   6. Re: RE : Re:  FASTRAX GPS (jim s)
   7. Re: FASTRAX GPS (jim s)
   8. Re: RE : Re: FASTRAX GPS (Hal Murray)


----------------------------------------------------------------------

Message: 1
Date: Wed, 2 Jul 2014 12:36:06 -0700
From: Chris Albertson <albertson.chris at gmail.com>
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] FASTRAX GPS
Message-ID:
	<CABbxVHskDYQNrPi8eSfnw6Odafrh3+c1LmJ8r+NLGeFSw_LV-A at mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

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
unbalanced.

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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-- 

Chris Albertson
Redondo Beach, California


------------------------------

Message: 2
Date: Wed, 02 Jul 2014 13:00:53 -0700
From: Alexander Pummer <alexpcs at ieee.org>
To: wojciech at owczarek.co.uk, 	Discussion of precise time and frequency
	measurement <time-nuts at febo.com>
Subject: Re: [time-nuts] FASTRAX GPS
Message-ID: <53B464F5.5060107 at ieee.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

the trick of every data line is; it has to me matched to it's impedance, at
least at the receiving end, other way it is ringing. Every pair of conductor
becomes transmission line as soon it's length exceeds " the length of the
rise time" of the signal which is traveling on it.
73
Alex

On 7/2/2014 11:46 AM, Wojciech Owczarek wrote:
> My 2c - RS232 is extensively used in data centres over cat5 with network
kit for out of band management via serial consoles, usually 9600 baud.
>
> I've done this many times via (multiple) patching panels/frames easily
over 100ft, ribbon/rollover then cat6 but also cat5. This kit tends to be
reliable and usually well grounded though. Well, and "compliant".
>
>
> Wojciech Owczarek
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to 
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------------------------------

Message: 3
Date: Wed, 2 Jul 2014 13:25:45 -0700
From: Chris Albertson <albertson.chris at gmail.com>
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] FASTRAX GPS
Message-ID:
	<CABbxVHv5Y5jm3ghe1L5x2vc7VngBJcq3x7Wm1etTPf5rc+11ZA at mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

On Wed, Jul 2, 2014 at 1:00 PM, Alexander Pummer <alexpcs at ieee.org> wrote:

>> I've done this many times via (multiple) patching panels/frames 
>> easily over 100ft, ribbon/rollover then cat6 but also cat5. This kit 
>> tends to be reliable...

Does this include the PPS signal on the DTR pin?  I think this is part of
the problem with a long serial cable and GPS.  The pulse is sometimes VERY
short.

Again, yes you could fix this by introducing circuits at each end.

And what were you sending?  Typically in an IT environment you'd be using
serial for the admin ports of routers and the like.  Basically you run
terminal emulators and it does not matter if one in 1,000 characters is
corrupted.  The data is not checksummed and you'd rarely notice an error.
The Binary TSIP data from a Thunderbolt is
checksummed and runs 24x7 so you notice every error.   But really, the
main problem was the PPS.
-- 

Chris Albertson
Redondo Beach, California


------------------------------

Message: 4
Date: Wed, 02 Jul 2014 22:29:14 +0200
From: Jean-Louis Oneto <jl.oneto at free.fr>
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: [time-nuts] RE : Re:  FASTRAX GPS
Message-ID: <xf88c8au92i3fmdsb4pyd6dh.1404332954557 at email.android.com>
Content-Type: text/plain; charset=utf-8

Hello,
AFAIK, the differential variant of RS-232 is RS-485. I'm not sure about the
levels.?
Best regards,?


Jean-Louis Oneto

Envoy? depuis un mobile Samsung?

-------- 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 unbalanced.

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.
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.



-- 

Chris Albertson
Redondo Beach, California
_______________________________________________
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------------------------------

Message: 5
Date: Tue, 01 Jul 2014 22:13:33 -0700
From: jim s <jwsmail at jwsss.com>
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] FASTRAX GPS
Message-ID: <53B394FD.9020707 at jwsss.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed


On 7/1/2014 8:27 PM, Hal Murray wrote:
> It's often easier to use a long serial cable rather than a long antenna
cable.
Excellent suggestion.  I will look at that as an alternative.  I wanted to
keep the FASTRAX and the unit is mated to near my systems, but for other GPS
setups with other chips that would be good.

Thanks
Jim


------------------------------

Message: 6
Date: Wed, 02 Jul 2014 14:49:17 -0700
From: jim s <jwsmail at jwsss.com>
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] RE : Re:  FASTRAX GPS
Message-ID: <53B47E5D.5040501 at jwsss.com>
Content-Type: text/plain; charset=UTF-8; format=flowed


On 7/2/2014 1:29 PM, Jean-Louis Oneto wrote:
> Hello,
> AFAIK, the differential variant of RS-232 is RS-485. I'm not sure about
the levels.
> Best regards,
>
>
> Jean-Louis Oneto
You have to control the direction  of RS485.  You don't have to with RS232.
One of the problems with support of RS485 in Linux OS kernels is that the
kernel can't respond to the turning of the line quickly enough in real time.
I had an application with 115k requirement, and it had to turn the line
within 1/10 of a bit time. Pretty quick for a kernel.

It is differential, and it does send data, but is a different beast in many
ways.

I would have liked to have had an external processor to handle the RS485,
and some chips do that, but we had the engineer just attach two serial ports
on an Arm SOC to the usual serial uarts, and it was fun figuring out how to
make it work.

BTW this was for communicating with an airframe, and the avionics dictated
the rate we had to turn the lines.  It was for passenger signals, etc., so
was simple, but you basically ran all the cabin lighting and attendant
signalling thru one line for the entire aircraft.


------------------------------

Message: 7
Date: Wed, 02 Jul 2014 14:52:47 -0700
From: jim s <jwsmail at jwsss.com>
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] FASTRAX GPS
Message-ID: <53B47F2F.5030401 at jwsss.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I noticed on Toms info page, (very good along with the two emails for
info) that there is no connection called out for the antenna power.

There are two power in pins, Primary and Backup power.  Since I'm going to
use an active antenna, can I send the 5 v up the antenna power, or will the
Primary power propagate and power the antenna?

The Antenna power is pin 1.

thanks
Jim

On 6/20/2014 8:31 AM, Tom Van Baak wrote:
> Hi Ernie, Jason, (also Hal, Chris),
>
> I'm able to get NMEA and 1PPS out of the Fastrax/iTrax130 board now.
>
> Before I sink any more time into this project, have any of you made 1PPS
measurements?
>
> Compared to ublox, using the same antenna, these units take tens of
minutes or even hours to lock. And they have a bad habit of being close to
UTC for a few hours but then gradually wandering off by tens or hundreds of
microseconds.
>
> A power cycle puts them back on track (aligned with UTC), so it would seem
to be a firmware issue rather than antenna or reception. A similar thing
happens on three different boards I have evaluated over the past two weeks.
>
> Now, when they are working right, the 1PPS has an RMS deviation of around
20 ns, which I've come to expect as typical for cheap GPS/1PPS receivers
these days. But the long lock times and unexplained 1PPS drift make them
unreliable for GPSDO or serious timing work, even at $12 each.
>
> It might be me, so I'm asking if you've seen anything similar. The binary
command set looks tempting, but I usually don't play with that until the
unit can be trusted to give reliable NMEA and 1PPS output.
>
> Unfinished page: http://leapsecond.com/pages/itrax/
>
> /tvb
>
> ----- Original Message -----
> From: "Ernie Peres" <ernieperes at aol.com>
> To: <time-nuts at febo.com>
> Sent: Wednesday, June 11, 2014 4:11 AM
> Subject: Re: [time-nuts] FASTRAX GPS
>
>
>> Hi Jason,
>>
>>
>> I figured out a different pin assignments....
>>
>> hold the PCB so that the SMA antenna connector is looking to right and
under the PCB.
>>
>> open-   1      2-  Ant power    presently connected to pin nbr 4
>>     TX-   3      4-  Main power  +3 volt
>>      RX-  5      6-  1PPS
>> open-   7      8-  Grnd   power -3 Volt
>>
>> the unit takes about 60mA @ 3,0 volt and comes-up in NMEA mode.. 9600
Baud.
>> I use the FASTRAX_WORKBENCH_522 software.
>> I wonder if anybody has other pin arrangement/connection. The 2 open pins
is UNK and also not sure if pin nbr 4 is the main power or perhaps the pin
nbr 2......??
>>
>> Rgds Ernie.
>>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>



------------------------------

Message: 8
Date: Wed, 02 Jul 2014 15:08:24 -0700
From: Hal Murray <hmurray at megapathdsl.net>
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Cc: hmurray at megapathdsl.net
Subject: Re: [time-nuts] RE : Re: FASTRAX GPS
Message-ID:
	<20140702220824.7348C40605C at ip-64-139-1-69.sjc.megapath.net>
Content-Type: text/plain; charset=iso-8859-1


jl.oneto at free.fr said:
> AFAIK, the differential variant of RS-232 is RS-485. I'm not sure 
> about the levels.?

RS-422 is the basic version:
  http://en.wikipedia.org/wiki/RS-422

RS-485 is the multipoint version.


Interesting comment from http://en.wikipedia.org/wiki/EIA-485

The EIA once labeled all its standards with the prefix "RS" (Recommended
Standard), but the EIA-TIA officially replaced "RS" with "EIA/TIA" to help
identify the origin of its standards.[1] The EIA has officially disbanded
and the standard is now maintained by the TIA. The RS-485 standard is
superseded by TIA-485, but often engineers and applications guides continue
to use the RS designation.

--
These are my opinions.  I hate spam.





------------------------------

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