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[aprssig] Should I develop an embedded I/F to Davis WX?

Spider spider at rivcom.net
Sun Aug 1 19:45:14 UTC 2004


Gary,

The Davis products are likely the most popular product.  However, it seems
every application that uses it's data requires the logger.

So if during your development you can come up with a way to provide data
right out of the unit, convert it to the standard WXNOW.txt file, then all
sorts of uses could be had.  Then, take the WXNOW.txt file and convert that
to APRS for your specific application.

That would be what I'd do if i was a programmer....but then, I'd be
dangerous if I was a programmer!!! ;)

Jim, WA6OFT

----- Original Message ----- 
From: "J. Gary Bender, WS5N" <WS5N at mindspring.com>
To: <aprssig at lists.tapr.org>
Sent: Sunday, August 01, 2004 10:22 AM
Subject: [aprssig] Should I develop an embedded I/F to Davis WX?


I am looking for advice for putting together an APRS standalone weather
station.
 I have real estate (eventually my retirement home) about 200 miles away.  I
also have way too much time on my hands.  I am thinking about writing my own
embedded interface to handle the data translation between my weather station
and
APRS/TNC.  I am competent to do the programming, but I am not sure I won't
be
reinventing the wheel.

Equipment:
  Davis VantagePro 6150
  MFJ 8621 Data Radio
  Tasco Telereader 211 TNC (with Japanese documentation!)
  -or- Pac-Comm Tiny-2 TNC
  12 VA sealed battery
  2.9 amp 21 v solar panel.

I remember using the Telereader years ago and it seemed to work with
conventional commands, so I can probably get by without having English doc.
It
is a nice small unit with low power consumption.  I don't think either TNC
would
impact my power budget much (200-250 ma).

What I need is a cheap way to fetch and convert Davis data to APRS weather
packets.  I probably should add some additional APRS intelligence to the
MCU.  I
will include some telemetry; things like battery condition and the state of
a
few switches/alarms.  I have not monitored traffic yet, but nothing shows up
near the 87315 zip code on FindU.  However, I can hear something every few
minutes full-quieting, so I probably have a digi I can hit.

I also have two Zilog Development Kits sitting here begging to be applied to
something useful.  One for the Z8Encore! And another for the Z8Acclaim!
Either
chip family has plenty of room for a lot of features.  I am guessing that an
interface can be put together for much less than $50 in small quantities.
We
are looking at the Z8... MCU, a voltage regulator, a TTL/RS-232 level
converter
or two, plus a few support components.

Basically I want to plug-and-play the Davis to the MFJ as easily as folks
say
the Peet Bros weather stations do.  It turns out there are lots of Davis
units
on eBay, so it is worth a couple hundred bucks to do it.

My questions:
1) Has this already been done for a low power solar environment?
2) Is there a list of TNC attributes that should be implemented at startup?
Reading the APRSSIG the last couple months, I see there are some parameters
that
a well behaved APRS controller should initialize.
3) Would there be enough interest in this sort of device for me to
generalize
the code so it can adapt to other weather stations and TNCs without too much
trouble?
 -- 
    Gary, WS5N
    Tijeras, NM  USA





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