Released source & Mac OS X binary to test serial port and Vantage Pro basic connectivity.
After poking around a bit more, it seems that meteo issues a wakeup "command" to the station before every attempt to retrieve the current image. It goes something like this:
That pretty much mimics the sample pesudo-code from Davis, which my stuff tries to mimic as well.
- issue "LOOP" command
- wait for ACK
- read reply packets
- update database
Within the bits of code that read data from the station, it seems that the meteo folks ran into the problem I'm seeing. They use signal-oriented watchdog timers around all of the reads. If any of them fail, it restarts the meteo process. Guess I wasn't exaggerating about how bad the serial interface is to this thing. I'll have to come up with a way of doing the same thing within a Cocoa-app. No wonder there aren't more projects around the Davis stuff. Perhaps the Java-based WeatherLink for OS X just does archive image downloads. I'll have to do some more poking.