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Weather Station Hardware => Davis Instruments Weather Stations => Topic started by: docbee on April 20, 2014, 04:33:07 AM

Title: Error in Davis documentation (2.61) regarding LOOP2
Post by: docbee on April 20, 2014, 04:33:07 AM
I spent quite some time to make use of the "gust of last 10 minutes" field in the LOOP2 packets to make sure my SW does not pass a wind gust not reported by LOOP live data (which can happen when LOOP pauses i.e. to allow WLIP logger to upload to Weatherlink network). The documentation says it is a 2 byte value in tenth of mph. This is wrong, it is just reported as mph. I don't know if the second byte is used at all and will hopefully not see gust speeds above 255 mph - and when so I will certainly not care most about what the LOOP2 packet returns ;-)

I appreciate that Davis documents the serial communication, therefore I will not rant about seeing bugs in the documentation. In case you are also into LOOP2 don't expect too much precision there... it more gives some hints what might be in... I did not test if the other wind speeds are reported as explained in the documentation... what is "resoluation" by the way?  :roll:

Title: Re: Error in Davis documentation (2.61) regarding LOOP2
Post by: mcrossley on April 20, 2014, 05:23:49 AM
The VP2 only reports wind speeds in integer MPH. The average speeds *could* be reported to 1dp, but I thought they were also reported as integer values.
Title: Re: Error in Davis documentation (2.61) regarding LOOP2
Post by: docbee on April 20, 2014, 05:30:26 AM
Yes, good old LOOP packets report just in plain mph (no decimals) and there it is documented right.
Title: Re: Error in Davis documentation (2.61) regarding LOOP2
Post by: johnd on April 20, 2014, 05:44:03 AM
I suspect this is either to cater for the Vue or for future use. The Vue ISS (but not the VP2 ISS???) can apparently report wind speed to 1dp when received by an Envoy8X. I've never really dug into this to confirm it or to understand how it can be (unless eg the Vue wind cartridge has two magnets (even assuming it still uses magnets), but the standard Vue console has a display limited to integer for some reason, perhaps to avoid embarrassing the VP2, but that's just me guessing, probably wrongly).
Title: Re: Error in Davis documentation (2.61) regarding LOOP2
Post by: docbee on April 20, 2014, 06:49:05 AM
As the RF protocol from the ISS (regardless Pro2 or Vue) just has one byte to offer to transport current wind speed, I doubt there is a chance to bring a better resolution than 1mph to the console. Console then can provide 1dp when doing some averaging math. So it is somehow logical that gust can only be at 1mph resolution, but the guy writing the manual didn't get it right.
Title: Re: Error in Davis documentation (2.61) regarding LOOP2
Post by: DeKay on April 20, 2014, 01:07:08 PM
Speaking of which, the documentation for LOOP2 documents the outside (and inside) temperature values as:

"Either the Average Outside Temperature, or the Final Outside Temperature over the archive period.  Units are (F / 10)."

How do I know which of the two values is reported?  If the former, over what time is the average calculated?
Title: Re: Error in Davis documentation (2.61) regarding LOOP2
Post by: ericfynne on April 20, 2014, 02:00:15 PM
How do I know which of the two values is reported?
From the setting of byte 0xFFC in the EEPROM data.
Quote
If the former, over what time is the average calculated?
As it says, it's the average over the archive period.

Eric
Title: Re: Error in Davis documentation (2.61) regarding LOOP2
Post by: DeKay on April 20, 2014, 06:37:26 PM
From the setting of byte 0xFFC in the EEPROM data.

Thank you, good sir.  I remember seeing that somewhere but couldn't find it again, despite being all over this document recently.