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

Ron Perry ronk at sunlinux.com.au
Sun Aug 1 23:00:57 EDT 2004

The might do the job.


On Mon, 2004-08-02 at 03:22, J. Gary Bender, WS5N wrote:
> 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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