Windchill data WMR200

[steve]

Cumulus Wind Chill: 16,7
Station Wind Chill: -19

I assume you've missed the minus off the Cumulus reading?

Here's the last wind packet in the debug log:

0250.990 : 11:03:34 Packet:D3 10 02 0B 0F 02 0C 0D 0C 26 B0 02 28 80 A6 02
0250.990 : Wind packet received

According to the (unofficial) protocol spec, the wind chill is in the 13th byte and is given in tenths of a degree Fahrenheit.

13th byte = hex 28 = dec 40 = 4.0F = -15.6C

I suspect the problem occurs when the wind chill goes negative (in degrees F). Presumably the actual value is minus 4F = -20C, and there is a flag somewhere in the packet which indicates a negative value - but where?

Edit: the top bit of the 14th byte looks suspiciously like it might be the flag: 80

[bard]

Cumulus Wind Chill: 16,7
Station Wind Chill: -19

Yes that is a typo.... it should be -16,7

[steve]

I've assumed that the top bit of the 14th byte is the sign bit for the wind chill, and I've put a zipped updated cumulus.exe here:http://nybbles.co.uk/downloads/Cumulus.zip

[bard]

I will try to test i later today...

~b

[mcrossley]

I suspect the problem occurs when the wind chill goes negative (in degrees F). Presumably the actual value is minus 4F = -20C, and there is a flag somewhere in the packet which indicates a negative value - but where?

Edit: the top bit of the 14th byte looks suspiciously like it might be the flag: 80

Looks favourite doesn't it. I've found a few packets from logs on the web and none of them have that bit set - and they are all +ve °F.

[bard]

I've assumed that the top bit of the 14th byte is the sign bit for the wind chill, and I've put a zipped updated cumulus.exe here:http://nybbles.co.uk/downloads/Cumulus.zip

I have tested now and it looks like it works fine now... Tanx :