[CA] [CA11] NMEA0183 Wind Steering on ST2000

[bretthoward]

I'm trying to get wind steering to work on my ST2000. But I'm building my own wind instrument. It has a wireless transmitter at the mast head that the wind instruments picks up and displays. Then there is also another unit that picks up the same wireless transmissions and it will transmit NMEA into the ST2000.

Right now I'm not on the boat but I'm just trying to get things debugged before I launch again in about a month. I have the reception of messages and formatting the NMEA working to the best of my knowledge. Here are some sample messages from a hard coded example that I've been trying to test with:

$IIVWR,042.0,R,1.2,N,0.6,M,2.2,K*4A
$IIVWR,045.0,R,1.2,N,0.6,M,2.2,K*4D

I have it send a message every 100mS at 42 degrees for 10 seconds and then I have the wind shift to 45 degrees...

So far I've tried hooking the 0-3.3V TTL RS-232 directly to the NMEA+ and NMEA- pins and that does not seem to work. I've also installed a buffer that should be bringing it to 5V but its a bi-directional buffer that uses pull resistors and that seems to only give a 0-2.5V signal strength.

I've ordered a full proper RS422 driver that I'll be installing here in the next couple days to test... But I've been finding that the unit does nothing when I press STBY and AUTO at the same time... Is it normal that it won't enter the mode unless it is receiving NMEA strings? I noticed that it will go into track mode even if messages aren't coming in so I was a bit concerned... Any help would be greatly appreciated!

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Brett,

As you have suggested, Raymarine equipment is designed to support differential RS-422 communications, not RS-232 communications.

Q1. Is it normal that it won't enter the mode unless it is receiving NMEA strings?
A1. Yes.

[bretthoward]

Ok then I'll have an RS422 buffer IC once I get the mail tomorrow. Here's hoping that everything just lights up and works once I get that piece in place.

[Chuck - Raymarine - Moderator]

You're welcome.

[bretthoward]

So with RS422 it does now go into W mode! Progress!

However it says W but it then shows the heading as the angle not the apparent wind angle.

Then as I turn the unit it seems to steer as though it is just in standard A mode (turns one way as I rotate one direction then turns the other way as I rotate past the set point in the other direction). This is all happening while the unit is sending the same fixed wind direction over and over...

I then wrote a module that fed the unit 45 degrees for 10 seconds then changed to 50 degrees for 10 seconds followed by 40 degrees for 10 seconds. The unit just some what pulsed every so often but remained fairly still steering wise... Perhaps the ST2000 is filtering out the very consistent data and assuming that it is fake?

Is their a recommended rate at which these NMEA0138 wind sentences should be sent?

Also I presume there is no issue with the unit sending both MWV and VWR sentences for every message interval? Seems that it would just ignore extra information.

[Chuck - Raymarine - Moderator]

bretthoward,

Raymarine products transmit wind data via a SeaTalk bus at 0.5 Hz and this data would be transmitted at 0.5 Hz from the NMEA 0183 output terminals of Raymarine's E85001 PC/SeaTalk/NMEA 0183 data bridge when interfaced to a Raymarine wind instrument. Should the instrument be transmitting MWV NMEA 0183 sentence to the autopilot, then there would be no need to additionally transmit the VWR sentence to the autopilot.