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[wxsig] Several T238+ questions from a newbie

William Beals will at beals5.com
Sat Aug 7 03:01:34 UTC 2010


Ted:

Hope things are going OK.  I do duplicate the data to the serial port when
in Modem mode, but clearly only using the 5-minute format.

That sparkfun project does look interesting for a simple logging scheme.

will

-----Original Message-----
From: wxsig-bounces at tapr.org [mailto:wxsig-bounces at tapr.org] On Behalf Of
Ted11
Sent: Sunday, May 16, 2010 11:43 AM
To: 'TAPR Weather Station SIG Mailing List'
Subject: Re: [wxsig] Several T238+ questions from a newbie

Great, thanks for all the useful information!  

1.  Manual:  Got it, thanks for clarifying.  

2.  1-wire length:  I should be able to keep the 1-wire cable well under 50
feet, so hopefully I won't have a problem there. 

3.  Computer and radio output:  I was about to look at the code to see how
this worked, but then looked at the manual again (page 3) and found this
under "UART/Display Options":

"All modes send the data out the UART port.  Selecting the modem mode also
sends the data out MX-614-based modem and still sends averaged data out the
UART."

This seems to suggest the system is already programmed to do what I want -
sending data to both the radio (through the MX-614 modem) AND the computer
(through the UART and then through the DCE).  Am I reading this correctly?
Or does selecting modem mode turn off the UART output?  I think I phrased my
initial question poorly - my hope was to use the on-board MX-614 modem to
send data to the radio, while using the DCE port to do data logging.  5
minute intervals are fine.  

4.  Data logging:  Psion is a great idea for this, I'm not sure I've ever
seen one in real life.  Newer Palms and PocketPCs don't have serial ports,
but the older ones do, although usually as a special connector.  

After more digging, I came across what might be a simple solution to the
logging problem:  

http://www.sparkfun.com/commerce/product_info.php?products_id=8627

A standalone, low power device for serial data logging, $60.  Looks like it
will take the DCE output and make text files out of it, which should work
just fine for me.  

Thanks again for all your help.  

Ted

-----Original Message-----
From: wxsig-bounces at tapr.org [mailto:wxsig-bounces at tapr.org] On Behalf Of
William Beals
Sent: Saturday, May 15, 2010 1:17 PM
To: 'TAPR Weather Station SIG Mailing List'
Subject: Re: [wxsig] Several T238+ questions from a newbie

Ted:

To your questions:

1) Good point, that is a leftover from the T238 where we had two different
DE-9 connectors, one for DTE and one for DCE.  That error has been there a
while!

2) How long you can run a 1-wire cable has been a topic of great debate over
the years!  While the theory why is murky, the best bet for longest runs is
cheap telephone cable, not Cat-5 cable.  50+ feet of telephone cable seems
to be pretty reliable, above that is where folk start running into
problems--but not all folk.

3) It is technically possible do have both the computer output and radio
outputs active at the same time and even at different intervals, but no
software for that has ever been written.  You are right in that they way
things are set up, you get modem output or computer output, not both.  

4) I think your idea for logging is a good one, the Palm and PocketPCs have
serial ports I assume.  I have some old Psion palmtop computers and I've
used them for terminals in the past.  Very handy and targeted to run from 2
1.5V batteries, so very power miserly.  The t238s have a sorta documented
feature whereby you can turn on the radio just before transmitting an turn
it back off again after the transmission is done for solar installations,
but I doubt that would be useful for a palmtop computer.

will

-----Original Message-----
From: wxsig-bounces at tapr.org [mailto:wxsig-bounces at tapr.org] On Behalf Of
Ted11
Sent: Monday, May 10, 2010 9:50 PM
To: wxsig at tapr.org
Subject: [wxsig] Several T238+ questions from a newbie

Hi, 

 

Finally finding the time to put together my radio and weather interests.
After getting my technician license a while ago (yeah, once they dropped the
code requirement), I decided a few years ago to do a career change and am
currently studying atmospheric science.   I've been asked to do some weather
monitoring and analysis for a local event, and it looks like the T238+ is
the best way to accomplish everything I want to do.  

 

Had a few questions as I start to dig into the project.  

 

1.  On page 2 of the operations manual (Rev 2, April 2005) the description
of J4 says, "Use either this header or J5, do not use both at the same
time."  I think this might be a typo, J5 is the 1-Wire interface and I would
think it should always be used.  If the manual is incorrect, which header
shouldn't be used with J4?

 

2.  Do you have a recommendation how far I can run the 1-Wire cable (between
the T238+ and the AAG instruments)?  

 

3.  Is it possible to have the unit do computer output (5 sec intervals) to
the Computer Data Connector (J4) while at the same time sending packet data
to the modem at 5 minute intervals?  The UART settings seem to suggest the
choice is either one or the other.  Is this a hardware or software
limitation?  Ideally, I would like to log the data locally, as well as send
it out via APRS, even if the local logging only happens at 5-minute
intervals.  

 

4.  As far as equipment necessary to log data from the serial port, the
obvious choice is a computer.  Down the road, I would like to set up the
weather instruments as a solar-powered stand-alone weather station for some
research work.  I won't have enough juice to run a computer, and there is no
nearby digipeater.  Seems to me a Palm device or PocketPC might be able to
log the data, but I'm not sure how to use any of those devices to log data.
Anyone have a suggestion for how to do this?  

 

Thanks for the help.  

 

Regards, 

 

Ted

KE6ROS 

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