Full Version: Nasa Marine wind masthead unit
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For the past couple of weeks I have been lurking here and last week I started putting things together. I bet some of you got sick and tired of me asking simple questions, so I thought I might as well put some info here that might help somebody else in the future. Smile

I started with a Raspberry Pi 4 (4GB) that I had sitting around. I installed OpenPlotter (that was pretty simple), bought a few GPS USB receivers (in order to test which one would be better) and I also got a DTech USB2 to RS422/RS485 adapter [] for NMEA0183 input/output.


I have been looking for a cheap wind head mast unit and last week I saw on Ebay a Nasa Marine Clipper Tactical Wind System (Apparent and True) [] that seemed to be going for about a third of the RRP, brand new in its box. I hit it, got it and it arrived in the post.

So, first I connected the RS422 adapter and connected it to SignalK. Initially I went for high speed connections (115200 baud) but later on I realised that I should use something more reasonable so I settled for 4800 (I don't think that the Nasa Marine instruments can do higher). I also had to disable the 'Validate Checksum'. The adapter RXD LED was blinking happily!


Then I connected the BLACK of the wind sensor (or the display, they are the same) to the GND of the RS422 adapter. The BLUE of the wind sensor (or the display) to the RXD+ of the adapter. The instructions say that it should go to '+ NMEA' but it didn't work. So, I tried the RXD- and it worked!

If all you want to do is to import wind data into SignalK then that's it you are done. You are cooking with gas!

But, the display that I have can show True Wind, too. In order to show that, it needs input either from the LOG or GPS. As I was not on the boat, all I could do is use some data from the GPS. It is not any proper motion, but due to poor reception the position jumps around a bit and it's good enough to see some data coming through. BTW, it would be great if somebody could create a service where we can pull simulated data from, with the option to pick and choose different sentences so we can test; just an idea!

So, I connected the T/R- of the RS422 adapter to the NMEA input of the display but there was no data coming in. I wasn't really expecting it, as the TXD LED of the RS422 adapter wasn't blinking at all. After I looked at the forum for different solutions and I tried all sorts of things, eventually through trial and error I saw the TXD LED on the adapter blinking. I needed to add "nmea0183out" to the 'Output events' field of the RS422 adapter in 'Data Connections' and edit the /home/pi/.signalk/settings.json file.
      "pipeElements": [
          "type": "providers/simple",
          "options": {
            "logging": false,
            "type": "NMEA0183",
            "subOptions": {
              "validateChecksum": false,
              "type": "serial",
              "device": "/dev/ttyOP_wind",
              "baudrate": 4800,
              "toStdout": ["nmea0183out"],         <----- I added this
              "appendChecksum": true,
              "removeNulls": true,
              "overrideTimestamp": false,
              "sentenceEvent": "",
              "suppress0183event": false
      "id": "wind",
      "enabled": true

I found the solution here: Then I went to the 'Convert Signal K to NMEA0183' plugin and made sure that both GLL and RMC were ticked with a throttle of 100. Initially I had set all sentences to be sent and the RasPi almost ground to a halt. So do not convert phrases/data that you don't need!

Eventually it all worked and the Nasa Marine display shows True Wind Angle and Speed!

All this exercise spurred me to clean things up a bit; I removed plugins that I don't really need so it is all more manageable. Also, I played a bit with the Derived Data plugin and I created some extra data, so I can have a wind direction of 90 P (for Port) rather than -90. I also created a "psuedo" True Wind Angle [without compass] (based on speedOverGround, AWA, AWS, courseOverGroundTrue).

The next big thing is to get from the Nasa Marine Clipper Duet the Speed Log and Depth into OpenPlotter. First I will try the NEMA0183 method found here for the simple reason that I already bought the Atmega 32u4. I sorted out all the code and all I need to do is find out which pins exactly I need to connect on the sensors.