WXT520 on RaspberryPi

[Andrew Terhorst]

Happy new year forum!

I have my WXT520 displaying data on the weewx web page in my bench test. I used the WXT520 driver sourced from https://github.com/matthewwall/weewx-wxt5x0.

For my bench test, I borrowed a Vaisala USB data configuration cable. I configured the WXT20 to send data in sdi12 format.

I have three questions:

1. The barometric pressure data is not being picked up. Where do I enable this data to be displayed?
2. I need to return the Vaisala cable. I have an M12 cable - can someone share with me the sdi12 wiring diagram to connect the data lines to the RaspberryPi?
3. Can I still use the WXT520 driver from https://github.com/matthewwall/weewx-wxt5x0 or does this work only with the Vaisala USB cable?

Thanks in advance.

[DR]

As far as question #2, have you wired to the screw-attached green wiring block INSIDE the base of the WXT and run a cable out through the gland-seal and attached that to your SDI interface to your computer to monitor the data stream?   If not, I can look to see if I can find the pin-out in one of my manuals a bit later today and get an image of the diagram to attach here for your reference.

When I was working with WXTs some time ago, I used the Vaisala USB programming cable only to send configuration information to the unit, and had RS232 (and the SDI when I played with it) connected directly to the inside board as the final configuration would have it when mounted outside.

I'm sure by now you have figured out that the WXT cannot be configured by sending commands over the other connections, and you had better make sure that the unit is configured exactly as you want (and most times you'll never change it from the set up you determine to be best for you) but it is a pain to want to switch outputs since you'll not only have to get a programming cable again, but also get the WXT down from the outdoors mount and put it back on the bench.  Grrr. 

Today is a busy day, but for diversion I hope to pull the manual and get the correct picture of the inside for you.

I take it you do not have the spiral bound manual for the WXT?  All these are laid out in there, along with all the commands to enable and configure the outputs.

What exact model of the WXT520 do you have?  Can you send the model number and the long string of letters and numbers which tell how your unit was built?

Dale

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[Andrew Terhorst]

Thanks. I have the wiring diagram for the Vaisala M12 pin-outs. See attached. I use brown for 12VDC+, red for 12VDC-, white for TXD, blue for TXD, and green for GND.

I am confused about how to connect these to the Raspberry Pi. The 12VDC cables connect to my solar-recharged battery. I am not sure if I can run RXD, TXD, SGND. My naive view of the world is that the Vaisala sends data at a set interval. We are dealing with one way communication. No polling is necessary? All I need to do is configure the Raspberry Pi and weewx to listen for the data? I do not need heating. Do I simply wire white to GPIO14, blue to GPIO15, and green to GND? Then how do I get weewx to listen to RXD?

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Andrew Terhorst

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