Issue 137 in wfrog: problem reading Outside Temperature values

[wf...@googlecode.com]

Status: New
Owner: ----
Labels: Type-Defect Priority-Medium

New issue 137 by lucapil...@gmail.com: problem reading Outside Temperature
values
http://code.google.com/p/wfrog/issues/detail?id=137

Hi,
I'm using the trunk version of wfrog code
(https://code.google.com/p/wfrog/source/browse/trunk/wfdriver/station/vantagepro2.py)
on OpenWRT OS for logging on a DB values from my Davis Vantage Pro2 station.
The only modifications I have made to the code concern adding the DB
logging.

After some observation time, I have noticed that, when I use the 'LOOP'
command for requesting the last values (in my case 25), I record some
incorrect values for Outside Temperature.
In particular, the wrong value is always the same, and is displayed in
decimal as 1802.61°C.
In general, I log some bursts of such records, in a number from one to six
wrong records, about every ten minutes. After the burst, it keeps on
recording right.
The values I read pass correctly the CRC control, so I assume it is not a
problem due to the serial communication.

I have tried to log the raw strings and to search manually the bytes giving
the wrong values. When I come to the 2 bytes concerning TempOut, I read
FF7F, which corresponds to 1802.61.

The following 2 rows contain the raw strings I read: the first one presents
the problem (ff7f in TempOut field), the second one is ok (b402).

4c4f4f0000 b104 0e75 0203 31 ff7f
ffffff7fffffffffffffffffffffffffffffffffffffffffffffffffffffff7f0000ffff00000000470d00000000a308ffffffffffffff0000000000000000000000000000000000002803062d890243070a0d
fa42


4c4f4f0000 b104 0e75 0203 31 b402
ffffff7fffffffffffffffffffffffffffffff43ffffffffffffff00001e93010000ffff00000000470d00000000a308ffffffffffffff0000000000000000000000000000000000002803062d890243070a0d
e720

Hope this is enough information to help me fixing the problem.
Thanks in advance,

Luca

Attachments:
problem_driver.py 22.2 KB

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Updates:
Status: Accepted

Comment #1 on issue 137 by jordi.pu...@gmail.com: problem reading Outside

Temperature values
http://code.google.com/p/wfrog/issues/detail?id=137

Hi,

Thanks for reporting the problem. It is indeed strange.

I assume that you have a datalogger attached to the Davis Station (serial
or USB?). I wrote the driver but do not have a datalogger. I have a direct
cable hack. The protocol is supposed to be the same with or without the
datalogger.

I'll take a look at the raw strings.

[wf...@googlecode.com]

Updates:
Owner: jordi.pu...@gmail.com

Comment #2 on issue 137 by jordi.pu...@gmail.com: problem reading Outside
Temperature values
http://code.google.com/p/wfrog/issues/detail?id=137

(No comment was entered for this change.)

[wf...@googlecode.com]

Comment #3 on issue 137 by jordi.pu...@gmail.com: problem reading Outside
Temperature values
http://code.google.com/p/wfrog/issues/detail?id=137

The raw strings seem ok. I mean, the CRC is good and the other fields seem
Ok.

Could you check the VantagePro console for errors?. I remember there is a
way to check all errors directly on the console. It could be a sensor error
which is being sent as is (the LOOP command sends data as it comes, not
from the datalogger).

[wf...@googlecode.com]

Comment #4 on issue 137 by lucapil...@gmail.com: problem reading Outside
Temperature values
http://code.google.com/p/wfrog/issues/detail?id=137

Hi,
thank you for your reply.
Yes, I have a serial data-logger but I don't have the VantagePro console. I
only use the weather station connected to the data logger.
Maybe this is useful: I have also checked with Davis Weatherlink software
if there were the same issues, but it seems not to record such values (e.g.
it shows average values, but also max and min are stored, so I guess they
would be written in these fields in case of values out of range coming from
the weather station).

[wf...@googlecode.com]

Comment #5 on issue 137 by jordi.pu...@gmail.com: problem reading Outside

Temperature values
http://code.google.com/p/wfrog/issues/detail?id=137

Hi,

I've checked Davis documentation and I think I found the answer: 0x7FFF and
0xFF indicate that the corresponding sensor has invalid data. Check page 38
of the following document:

http://www.davisnet.com/support/weather/downloads/software_dllsdk.asp
http://www.davisnet.com/support/weather/download/VantageSerialProtocolDocs_v261.pdf

IMO WeatherLink just ignores these values.

I'll leave the issue open so that when time allows, something is done when
these values are received. Of course, any contribution is welcome!

Jordi.