Raspberry Pi Forums

torkelmj

I have some more questions: struct.unpack_from('B',s,1)[0] In this case, B is the data type and length you wan to extract, right? That would be a 1 byte integer; s is a container for the received data, for example, from LOOP 1; and 1 is the offset, the position of the desired data. What I don't kno...

torkelmj

Most bulletproof approach: use CRC-verified data only.

torkelmj

Sorry if my reply was perceived as a rather rude one. The curse and blessing of mobile devices: too easy to write (too) short posts from an on-screen keyboard.

torkelmj

...then you assume that the OP intended to write "LPS 2" in his original post. He specifically asked for "LOOP 2" which may very well return two identical data packets.

torkelmj

I've been reading the Davis documentation about the serial communication with the console, and there is something i can't really understand about the LOOP package. I mean, when I send, for example, LOOP 2, what is the difference between the 2 packages I receive? I haven't seen any explaination abou...

torkelmj

I'm pretty sure I do have V3 of the equipment, I also did get a davis datalogger though, will I have authentication issues with this? Does the V3 have different commands I have to run to get this working, I'm talking over ttyUSB0 on a raspberry pi and I can't seem to get anything to respond into th...

torkelmj

Are you a victim of the Davis firmware v. 3.xx problem?

http://meteo.annoyingdesigns.com/DavisSPI.pdf

torkelmj

It's all described here:
http://www.davisnet.com/support/weather ... s_v261.pdf

Section X - data formats (pg. 21-) refers.

torkelmj

BTW, here is a writeup of stuff which may be of use to those troubled by firmware version 3.xx:

http://meteo.annoyingdesigns.com/DavisSPI.pdf

torkelmj

As a string ... it doesn't look pretty.

torkelmj

En anglais...

http://meteo.annoyingdesigns.com/WOSPi.pdf

torkelmj

While communicating with the Vantage Pro station over USB and the FTDI breakout can be nice, it still adds the extra USB overhead which you don't really need. You may want to consider taking a step back and look at serial-line communication directly from the RPi to the VP console. It works fine, and...

torkelmj

Some of this stuff may be useful:
http://meteo.annoyingdesigns.com/WOSPi.pdf

Best of luck.

torkelmj

There are quite a few details available here: http://meteo.annoyingdesigns.com/WOSPi.pdf Actually, it's a complete guide to everything you need to get going. ...and the time budget, if a Davis Vantage Pro2 Plus is already installed: - 1 hr of online shopping for required hardware - 1 hr for assembli...

torkelmj

But two points on cost. First, the official logger is really not so costly - about GBP85+VAT in the bundle that's usually bought in the UK (and bearing in mind that a VP2 station will typically cost in the range GBP500-1000 depending on spec). I'd say that's rather costly for a device which (a) doe...

torkelmj

Very valid points. STILL - your bring up another interesting issue. Why on earth would Davis Instruments restrict access to the console, forcing the use of their own dongles only - effectively crippling a popular product? Unfortunately, there's only one answer to that question: $$$. They're biting t...

torkelmj

I bet your iPad doesn't produce too much meaningful data on its own. At least mine doesn't. And I don't expect it to output too much interesting stuff. And ... reading the product details of the VP2 on the davisnet.com website, it still seems to be a mighty fine weather station. That's what it is. I...

torkelmj

Davis Instruments obviously needs to be made aware of terms such as "backwards compatibility" and "documentation". If nobody tells them, they'll never know there's a market demand for these things. My console. My data. Don't lock it down, it's a waste of time - sooner or later there will be a workar...

torkelmj

Very interesting. Indeed! Especially the fact that Davis doesn't mention anything regarding an interface specification "lockdown" in their own documentation. Shutting off access to weather data in their weather stations will effectively make the unit completely useless ... even with existing Davis a...

torkelmj

Now, why is that? It works great on the 1.90 firmware. The latest Davis documentation for the serial protocol (dated August, 2012) doesn't indicate any upcoming design changes. ...and was there ever a version 2.xx firmware around? (Edit: firmware v. 1.90 still the only version available here: http:/...

torkelmj

The plan is to make a rather detailed writeup once everything is complete (it mostly is...), including all details from part numbers at Farnell to most of the Python code. All I need now is the time to put together all the documentation in a good-looking format. That's the boring part, I guess. I co...

torkelmj

Checking the Davis documentation, they've updated their documentation and now also describe the use of the LOOP2 packet. That's interesting, it contains even more wind data (10-minute gust velocity, 10-min average wind speed, 2-min average wind speed) but it lacks the forecast icon value. It works, ...

torkelmj

The wiring is the easy part. Three wires required. Both devices expect 3.3V. Davis <---> RPi GND <---> GND (P1 pin 6 - labelled GROUND) RXD0 <---> TXD (P1 pin 8 - labelled GPIO14) TXD0 <---> RXD (P1 pin 10 - labelled GPIO15) For a test setup, you'll be good to go with ordinary "female" jumper wires....

torkelmj

freedomotic wrote:Hi,
very interesting. Are you using raspbian or debian squeezy distro?
Regards

Running with the default RPi stuff - seems to be pretty stable, too:

PRETTY_NAME="Debian GNU/Linux wheezy/sid"
NAME="Debian GNU/Linux"
ID=debian

torkelmj

I've finally found time to "port" the Python code from the BeagleBone project (last summer) to the Raspberry Pi. It works quite well, "talking" to the Davis Vantage Pro2 weather station via the expansion header at the back of the weather station. No USB stuff or Davis interface dongles involved, jus...

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