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[wxsig] T238+ and AAG Sensors

William Beals will at beals5.com
Mon Apr 27 03:50:30 UTC 2009

Rui and Rich:


I've been procrastinating simply because I'm not sure what to do next.  By
all outward appearances, the sensor *should* work.  As best I can tell,
there is something not going right at some obscure wiring level or during
the installation process.  I've been thinking I just need to get one of them
and fiddle (the real reason for procrastinating).  Let's try a few debugging
things via email and if that doesn't work, I'll do just that.


The "No IDs Programmed" message happens if there is no temperature sensor ID
programmed.  I figure if you have any sensor at all, it had better be a
temperature sensor (and a DS18S20 at that).  So, you could be getting that
message if you erased all other sensors and just programmed in the TAI-8540
and nothing else.  I assume you have some device with a DS18S20 on it, so
can at least program that sensor into the T238.


Also, there are two sensors that use the DS2438, the humidity sensor as well
as the BP sensor.  As you go through the sequence of programming sensors,
the first one I look for is Humidity.  I go search for DS2438s, if I find
one I assume it is for humidity and program it.  If I find two, ask you to
either pick one of disconnect the BP sensor and re-run.  


I don't think this is a setup problem, but by first programming in a
temperature sensor of some kind and then letting me know exactly what
messages you get as you add the humidity sensor will help me get an idea of
what questions to ask next.  If, as you add sensors could you relay to me
the messages you get on the screen and what actions you take, that would


Another thing to do if it is possible on the TAI-8540 is to measure VCC to
the humidity sensor (+ side of C1 or pin 5 of the DS2438.  A voltmeter is
fine, but your oscilloscope would be better as it would do a better job of
catching any glitches.


Let's try a couple rounds of debugging via email.  If they don't reveal
something obvious, I will go ahead and get one of the AAG sensors.  I
appreciate the offer of a loaner, but to provide any kind of decent support,
I'll need one at my disposal.  





From: Rui MR Pinto [mailto:ct2jko at ct2jko.com] 
Sent: Sunday, April 26, 2009 4:01 PM
To: William Beals
Subject: T238+ and AAG Sensors


Hello Will,


You probably don't remember my case anymore but in February I bought a kit,
put it together and got a TAI-8540 Humidity sensor from AAG, which is
similar to the one from TAPR (Same chip, same schematics. I'm sending them
again on attachement). But I don't get any readings from this. I tested the
sensor with a USB 1-wire adapter (DS9490R) and the sensor works fine.
Putting an oscilloscope on the line, we can see there is some communication
between the sensor and the base when making the setup (a lot more pulses
than If I have no sensor on the line), but after running the setup and I try
to see the current data i receive: No IDs programmed, run setup. It's like
It doesn't recognise or memorize the sensor. I updated to the last software
version but it didn't change a thing, as I expected.


Is there any way you can help me out with this? I can even send you the
sensor in the mail (since you promise to give it back) so that you can play
a bit with it and see what's happening! AAG humidity, temperature and
pressure sensors could be an alternative to the kits by TAPR. The other day
there was a Rich Beckwith <rjbeckwith at gmail.com> on the mailing list, asking
if anone knew if these sensors worked or not with the T238, so it seems I
was not the ony one with this idea.


Thanks for your time and all the best,


Rui MR Pinto



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