[Xastir] Xastir and Ultimeter weather station

[Rick Green]

Here's what the Peet bros FAQ has to say about the ultimeter data format:

(quoting from http://www.peetbros.com/shop/custom.aspx?recid=5#Q6)

ULTIMETER MODELS 2000, 800 & 100 SERIAL DATA SPECIFICATIONS
(see above for ULTIMETER II Serial Data Specifications)
GENERAL

     * 2400 baud, 8 data bits, 1 stop bit, no parity.
     * ASCII hex digits (0 - F).
     * All fields are 4 bytes except 2 bytes where indicated in the 
complete record mode.
     * Most significant digit first.

NOTES:
1. IGNORE THE FIRST TWO DIGITS OF WIND DIRECTION. THESE DIGITS ARE 
NORMALLY 00, BUT IF A DIRECTION CALIBRATION NUMBER HAS BEEN ENTERED, THEY 
MAY BE FF.
2. RAIN GAUGES THAT MEASURE IN INCREMENTS OF 0.1 MM ARE FULLY SUPPORTED ON 
THE ULTIMETER LIQUID CRYSTAL DISPLAY. ANY PROGRAM OR DEVICE USING THE 
SERIAL DATA OUTPUT MUST UNDERSTAND THAT THE DATA IS IN 0.1 MM INCREMENTS. 
SERIAL OUTPUT FOR ALL OTHER RAIN GAUGE SELECTIONS IS REPORTED IN 
INCREMENTS OF 0.01 INCHES.

     * Data Logging Mode (Default Output Mode) Press CLEAR + WIND SPEED for 
3 seconds.
       While in this mode, records are sent out continuously at up to about 
90 per minute. The total record size is 40 hex digits + header, carriage 
return and line feed.

/snip/

DATA LOGGING MODE - RECORD STRUCTURE

     *
       Header = !!
     *
       Data Fields
           o 1. Wind Speed (0.1 kph)
           o 2. Wind Direction (0-255)
           o 3. Outdoor Temp (0.1 deg F)
           o 4. Rain* Long Term Total (0.01 inches)
           o 5. Barometer (0.1 mbar)
           o 6. Indoor Temp (0.1 deg F)
           o 7. Outdoor Humidity (0.1%)
           o 8. Indoor Humidity (0.1%)
           o 9. Date (day of year)
           o 10. Time (minute of day)
           o 11. Today's Rain Total (0.01 inches)*
           o 12. 1 Minute Wind Speed Average (0.1kph)*
     *
       Carriage Return & Line Feed

*Some instruments may not include field 12, some may not include 11 or 12. 
Please contact Peet Bros. if this presents any problem.
Total size: 40, 44 or 48 characters (hex digits) + header, carriage return 
and line feed.

(end of quote from Peet Bros FAQ)

Last year at Dayton, I bought a Peet Bros U100 as a 'factory refurbished' 
unit.  When I got it home and opened it up, the box contained a control 
unit marked 'Ultimeter 500', which appears to be essentially a U100 with 
the addition of a built-in indoor temp sensor.  It appears to output a 
datastream compatible with the U100, U800, U2000 spec above.  Here's a 
sample:

!!000000BD00D70000----0215--------001602FF00000000
!!000000BD00D70000----0215--------001602FF00000000
!!000000BD00D70000----0215--------001602FF00000000
!!000000BD00D70000----0215--------001602FF00000000
!!000000BD00D70000----0215--------001602FF00000000

So, mapping this against the spec from the FAQ, I get:

!! - Header indicating 'data logging mode'
0000      o 1. Wind Speed (0.1 kph)
00BD      o 2. Wind Direction (0-255)
 	( I sent Curt personally yesterday a note documenting what I
 	believe is a bug in the implementation of Note 1 on this field.)
00D7      o 3. Outdoor Temp (0.1 deg F)
0000      o 4. Rain* Long Term Total (0.01 inches)
----      o 5. Barometer (0.1 mbar)
0215      o 6. Indoor Temp (0.1 deg F)
----      o 7. Outdoor Humidity (0.1%)
----      o 8. Indoor Humidity (0.1%)
0016      o 9. Date (day of year)
02FF      o 10. Time (minute of day)
0000      o 11. Today's Rain Total (0.01 inches)*
0000      o 12. 1 Minute Wind Speed Average (0.1kph)*

I have no rain, barometer, or humidity sensors.  As we can see, the 
ultimeter is reporting '----' which is a pretty clear missing data 
indication for the baro and humidity values, but its reporting the 
misleading '0000' for the absent rain values.

I don't remember this being a problem when I first set it up, but a week 
or so ago, I noticed clearly bogus values (~40.06 inches hg!) showing up 
regularly in the barometric pressure value on the 'own weather data' panel 
and in the transmitted values.  I have no idea where this is coming from!

-- 
Rick Green, N8BJX

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."
                                   -Benjamin Franklin