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[aprssig] aprssig Digest, Vol 57, Issue 4

Dave Skolnick dskolnick at gmail.com
Wed Mar 4 14:28:10 UTC 2009


Kevin, et al

> Boat instruments that collect wind info and water temp are pretty common.  The
> sentences I can think of are MWD - wind direction and speed, and MTW - water temp.  I'm
> not sure if there are any that use the WX strings, or if there are any NMEA sensors
> common to boats that will measure rain, humidity, air temp.  Some of the newer ones
> may do barometric pressure.

I think some of the newer multi-function masthead sensors (acoustic?)
that measure wind speed and direction also have pressure sensors in
them. They may be NMEA 2000 devices though. NMEA 2000 is definitely
going to dominate, but I'm not ripping out all my existing kit to
implement it. There is a lot of NMEA 0183 out there.

Incidentally, I contacted Oregon Scientific some months ago to suggest
that a NMEA input to one of their weather displays might find an
appreciative market--I've seen the units on many many boats both power
and sail--but nothing came of it.

> I'm looking into the possibility of using a Sheevaplug or some other low-power Linux box
> coupled with a USB LCD to serve as the interface on my boat and provide some additional
> calculated functions.

The form factor and power consumption are attractive, but 12VDC would
be nice for marine/RV/mobile.

> An NMEA interface to APRS may exist, but the subset of boat owners with Seatalk
> networks that would want to broadcast APRS weather has to be a small pool.  I have a
> spare E85001 Seatalk-NMEA interface if you're interested.

I agree. Effort on an APRS interface should be based on NMEA 0183. I
have two E85001s in my system (Swedish boat builders have some odd
ideas). Both failed last year under warranty and it appears at least
one of them has failed again. The NMEA interface is what keeps dying
interestingly enough. The SeaTalk side and the SeaTalk on RS232 keep
working. That is high on my list since the E85001 is how I get NMEA
0183 position to the DSC of my Icom marine VHF and HF radios. That's a
long way of saying that yes, I am interested in your E85001. *grin*

> I'm also considering putting this (low-power Linux device + USB LCD) together as a mobile
> APRS solution.
> For about $200 in parts it would have an LCD with 7 key keypad, ability
> to use a USB keyboard

I'd be happy to help with a project like that. I'm fine with C and
Perl, no C++, little Java. I rock with regular expressions. *grin*

My priorities are 12VDC, the marine NMEA 0183 input, APRS position and
WX output (which appears to mean sentence conversion) for 1200 bps on
VHF and 300 bps on HF.

Hmm. I wonder if I can get data out of my battery monitor. That would
be interesting. So would temperature in the reefer and the freezer.

I have a similar data-logging project I've been working on (slowly)
that might have some synergies we could talk about. I live on my boat
so space for a lab-bench has been an issue. *grin* Software
development however is compatible with my space limitations.

> messaging, and depending on the radio it might be possible to add control features to it

Very cool, and interesting. I think there is some real potential,
especially as more cruising sailors get ham licenses. Something
inexpensive that allows giving back (WX information flowing back to
NWS, especially with data not commonly collected like water
temperature) and has some value-added functionality (messaging) would
be interesting.

Maybe the RV crowd would be interested as well, although the
instrumentation infrastructure isn't there like on boats.

Regarding Bluetooth, I wonder if a terminal program on a
Bluetooth-enabled laptop could be the messaging interface to the box?

> First things first though is handling APRS data streams and writing a basic menu system
> for the LCD.

Let me know what I can do to help.

sail fast and eat well, dave KO4MI
S/V Auspicious WDC9882



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