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Windseeker
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177 Posts
Discussion Starter · #1 ·
I have a Nexus instrument setup. This has a serial out (RS232) that operates in FDX mode. I use their race software to calibrate, and have it forward data to my own software that I use for performance analysis.

What I would like is to have a second connection with NMEA out. That way I can use iRegatta and it would be always live and on the boat even if my laptop is not.

The FDX server has NMEA out connections, and I've purchased RS422 -> Rs232 -> Wireless convertors but I'm unsure how to wire the RS422 -> RS232 convertor into the NMEA out on the server.

I've attached images of the server and convertor (and the 422 convertor pin listing)

Any help appreciated!!!
 

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Windseeker
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177 Posts
Discussion Starter · #2 ·
One thing I should say is my initial attempt had the Output A / B connections going to T/R +/- and I connected the ground. I didn't get a signal but I'm not sure that there wasn't a failure further down the line. My next step is to use my own code to test for connection on the RS232 side and to use a multimeter and look for voltages to see what I can see.
 

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I'll try a rough shot at this, not sure but here's my guess.

The 422 stuff is differential (no ground). There will be a transmit pair and receive pair. The transmit pair from one device connects to the receive pair from the other device (I'm not sure from your description, but you might not have done that).

It looks like the NEMA source (422) has only a transmit or output (called A and B) which need to connect to the receive pair (A and B) on the RS422/232 converter. It sounds like you may have connected to the wrong pair on the converter.

Given the source seems to only have an out, I believe this will be a receive only application.

Again, I'm winging it.
 

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Windseeker
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177 Posts
Discussion Starter · #7 · (Edited)
The only "ground" I think is the for 12 volt power to the RS232/422 adapter, and on the DB9 connector (RS232 side). The 422 stuff doesn't have a ground. Hope this works!
It did help!

Switching over to the receive pins and swapping the +/- got me a signal with or without the ground and I was able to read NMEA messages from the RS232 connection. The convertor seems to be needed to get a valid signal and it must be getting power from the other end as I haven't hooked up it's power connections. Might still need to though as I'm not sure my wireless hub will power the convertor - am assuming it does until proven otherwise.

Still working on getting the RS232 -> Wireless part functional, might have that now we'll see. The device I'm using was a $50 keynice unit that in theory will provide multiple TCP connections to read the same NMEA data stream over the wireless connection (and possibly could write too once I get to that stage). Problem is the manual is a bit thin on details but I think my main issue has been understanding which IP to connect to to read the relayed data. Think I figured it out last night but will have to confirm on the boat.

Many thanks :)
 

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Windseeker
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177 Posts
Discussion Starter · #8 ·
Boring update - the RS422 -> RS232 convertor I have doesn't work when attached to the rs232 -> Wireless convertor, looking at the pin diagrams it seems the wireless unit isn't providing power so I'm going to need a RS422 -> RS232 convertor with a power input. Not sure if this is fun or a pain in the ass but I'm learning.... So far I've got a complete unit cost of ~110$ vs $270 for a proper marinized unit (NMEA -> Wireless) which given my time spent is starting to look like a good investment.

Once I have something up and running though I'll document the whole setup so anyone finding this thread can take a step less than I have.
 
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