I dug up some info on the Davis WeatherMonitor protocol that someone else
gave me almost ten years ago, maybe it will help. I've never tried it myself
so I have no idea if it works.

=======================================================================
The instrument does not use RS-232 signal levels they are TTL level.

To get current readings send "LOOP + 0xFF + 0xFF + 0x0D" (7 bytes) @
2400baud, no parity, 8 data bits, 1 stop bit.

The WxMonitor responds with 19 bytes of data that are:
Byte(s)  Value
1        always 6
2        always 1
3 + 4    indoor temperature * 10
5 + 6    outdoor temperature * 10
7        wind speed
8        wind direction
10 + 11  barometric pressure * 10
12       indoor %RH
13       outdoor %RH
14       rainfall in hundredths
15       unknown
16       unknown
17       unknown
18       unknown
19       unknown
=======================================================================

The info I have gave no clue as to what units of measurement it spits out.

Hope this helps,
Paul

>
> I own a Davis Perception II weather station. It can be connected
> to a RS232
> port, not directly but using a box called DataLogger.
>
> I found in Davis web page a reference for the RS232 side, but I would like
> to connect a PIC directly to the station.
>
>  Does anyone knows the protocol that this weather station speaks?

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