RS485/NMEA0183 Connection to Simrad AT10

Electrical and electronic topics for small boats
IndigoJon
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RS485/NMEA0183 Connection to Simrad AT10

Postby IndigoJon » Fri Jul 15, 2022 12:16 pm

Hello,
New member in this Forum, longtime Bowers Harbor sailor and electronics enthusiast. I have done most of the wiring aboard Indigo, an Island Packet 37, but a recently installed Calypso Ultra Low Power Wired Anemometer is giving me fits. I cannot figure out how to connect the Calypso cable to the AT10 Converter cable to successfully input the NMEA 0183 MWV data into the NMEA 2000 network.

As stated in the subject, Calypso says the data is "RS485/NMEA 0183". The diagram of the data source says:
"RS485/MODBUS RTU OUTPUT" and the cable from the anemometer has four wires:
    Ground (Power -)
    VCC (Power +)
    Data (A +)
    Data (B -)
So far the only way I have seen the MWV sentences is by connecting those 4 wires to a USB converter (https://smile.amazon.com/dp/B0779983LH? ... =coa_us-20) and viewing the sentences on a laptop using Actisense's NMEA Reader. Connection to the AT10 cable has been unsuccessful...the AT10 is seen as a connected device on the N2K bus, but no NMEA 0183 information is passed to the N2K network.

The AT10 cable has the following connections:
AT10 Cable.PNG
AT10 Cable.PNG (32.79 KiB) Viewed 4529 times


I had seen a February 2013 Article by Jim Hebert entitled "Guide to NMEA 0183 Interconnections", but I am having trouble figuring out which of the diagrams (if any) apply to my situation, so I would really appreciate if anyone can give me direction on how the two devices should be connected for the sentences to flow properly.

Thank you,

Jon Kinne
s/v Indigo
IP37-5, Bowers harbor, MI

jimh
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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby jimh » Fri Jul 15, 2022 5:33 pm

If indeed the Calypso device will output NMEA-0183 sentence MWV then connecting to another NMEA-0183 device ought to be straightforward.

The signal that Calypso calls "Data A" is better named TALKER A. I don't know the wire insulation color.
The signal that Calyypso calls "Data B" is better named TALKER B. I don't know the wire insulation color.

To interface to NMEA-0183 you connect TALKER A to LISTENER A and TALKER B to LISTENER B.

On the SIMNET device, based on the legend in the illustration above, the input signals are

LISTENER A = WHITE
LISTENER B = BROWN

This wire insulation scheme is actually backwards, as normally in proper NMEA-0183 wire insulation colors WHITE and BROWN are TALKER A and TALKER B, but I suspect that SIMRAD did this intentionally so that when interfacing their device to a NMEA-0183 device the wires could be connect to color-on-color, making the interconnection simpler, perhaps in the minds of the SIMRAD engineers.

IndigoJon
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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby IndigoJon » Fri Jul 15, 2022 9:13 pm

Thank you Jim, but I went over to the boat and connected as you noted, and I still see no MWV on the N2K network. And although the AT10 shows up when I run NMEA Reader on the laptop, if I go to my Simrad autopilot and run a search for sources, the AT10 does not show up as a source for "Apparent Wind" (which was being listed before I made the most-recent interconnection change).

I don't know if it will help or not [IT DOES NOT HELP], but to give you the most information, here are the specifications from Calypso [what was posted was an image of URL--please do not post pictures of URL resource, just post the URL. In this case the URL is

https://calypsoinstruments.com/shop/product/ultra-low-power-ultrasonic-wind-meter-6#attr=38,56,65 ]

A page from the Calypso manual:
Calypso Data.PNG
Calypso Data.PNG (71.83 KiB) Viewed 4510 times


Should I conclude from your comments that the fact that I only saw the 0183 sentence on the laptop when the input from the anemometer was via the RS485 USB converter, is not of significance?
This is a real puzzle for me, but I know I am at the correct place, because it's clear that you know more about this than either the tech support people from Calypso or Actisense. The Actisense guy spent 2 hours on a remote connection and finally just gave up, and Calypso do not seem to know much about this. They just pointed to the AT10 diagram.

I really appreciate your help.

jimh
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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby jimh » Sat Jul 16, 2022 9:52 am

If you can monitor the NMEA-0183 output from the Calypso device and see the NMEA-0183 sentence MWV, and you have properly connected the the NMEA-0183 output to the protocol convertor, the most reasonable conclusion about why you don't see wind speed data on the NMEA-2000 network is the protocol convertor does not know how to convert MWV into NMEA-2000 data.

The speed of the NMEA-0183 connection appears to be variable. I don't know how you would alter the speed. The usual speed for NMEA-0183 is 4800-baud. The baud rate must be set properly in order for the protocol convertor to read the data. Also, what is the protocol convertor expecting as the baud rate?

If the protocol convertor is properly documented, it should give a list of the NMEA-0183 sentences it can convert and the parameter group number (PGN) that they will be converted to.

I also found this sentence on the manufacturer's website:

The Ultra Low Power Ultrasonic wind meter can output an NMEA 2000 signal when using an NMEA Connect Plus NCP_W2000 model.


That seems like the best approach to getting this information onto NMEA-2000 from the device.

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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby jimh » Sat Jul 16, 2022 10:07 am

From the illustration above, the NMEA-0183 output appears to be

TALKER A = GREEN (inferred from "Data +")
TALKER B = YELLOW (inferred from "Data -")

Note: that is completely backwards from the normal wire insulation color coding.

What is not clear to me: How do you set the output mode?

Apparently you have to make a receive and transmit connection using RS-232. In RS-232 mode the NMEA-0183 signal names would then be

TALKER A = GREEN
TAKER B = not provided

LISTENER A = YELLOW
LISTENER B = not provided

To interface when the device is in RS-232 mode, the connections would then be:

TALKER A = GREEN ---> LISTENER A
Ground = WHITE -----> LISTENER B

IndigoJon
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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby IndigoJon » Sat Jul 16, 2022 10:58 am

The reason I didn't order the gateway from Calypso that you referenced is that 1) it's about $400, and 2) they don't have any availability until December. Additionally, I already had the AT10, and it says it does support translation of MWV.

The Calypso is configured using what they call their "Configurator", a program I downloaded to my laptop, and then over that same RS485/USB converter connection, I set up the anemometer. Here is a screenshot of the "Configurator" so you can see what the options are:
Cconfigurator Screen.PNG
Cconfigurator Screen.PNG (31.65 KiB) Viewed 4485 times


I set it at 4800 and "Stream" mode...I don't know if that was correct and the Calypso support people didn't seem to know what should be used for a boat! If you look at their website, they promote the use of the anemometer for many different applications.

I'll go to the boat now and try what you suggested.

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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby jimh » Sat Jul 16, 2022 11:20 am

It sounds like the engineers who designed the device did not clearly communicate to the marketing company. This happens all the time. To get the real story, you often have to be handed over to the engineer, not the product manager.

IndigoJon
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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby IndigoJon » Sat Jul 16, 2022 8:49 pm

Jim, I tried those connections at the boat and still no data

I looked at the "Technical Data" sheet for the anemometer and it says the data format is "RS485", but it doesn't mention NMEA 0183 anywhere.

Is there some kind of conversion that takes place to make it 0183?

Remember that the only time I have seen the 0183 MWV sentence is when the ULP was connected to the laptop USB port by the RS485/USB Converter:

Is that converter doing something that needs to be done to the ULP data stream when connecting it to a 0183 device like the AT10 instead of a laptop?

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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby jimh » Sun Jul 17, 2022 8:33 am

The RS-485 communication protocol is a bus protocol, that is, devices can both send and receive on the same two wires.

The RS-232 communication protocol is a point-to-point, one way communication, TALKER to LISTENER.

NMEA-0183 began with RS-232 as the communication protocol but evolved to RS-422. R-422 is similar to RS-232 but uses balanced signals. This is why I recommended you set up the device you want to communicate with NMEA-0183 as an RS-232 output. RS-232 output can be easily interfaced to a newer RS-422 input.

Whether RS-485 can be directly connected to NMEA-0183 is unknown to me.

When the device says it has "Data Format NMEA-0183" the device is talking about how the data is formatted, that is, it will use NMEA-0183 data structures like the sentence name MWV and the content of the MWV sentence. But it sends this data using the electrical characteristics of a data communication standard called RS-485 also sometimes called MOBUS. Using of NMEA-0183 sentences is very common, as the protocol is old (c.1983) and many products use it to format the data they want to send to other devices. It is a common language.

In real NMEA-0183 connections, the electrical characteristics of the data communication is either RS-232 of RS-422. These are specifications for the electrical nature of the signals, not for how the data is to be formatted.

The other electrical data communication specification mentioned by the device is "UART/TTL". If you can configure the UART to operate in RS-232 or in RS-422 model, then you will be able to interconnect to a NMEA-0183 LISTENER. If the UART only works at TTL voltages, it may not work with an NMEA-0183 LISTENER.

An interesting comment about connecting an RS-422 receiver (or in other words a NMEA-0183 LISTENER) to an RS-485 bus (in other words, the device you have) can be found at:

https://www.edaboard.com/threads/compat ... -422.8051/

In that thread a contributor mentions:
RS422 is a one way bus: one transmitter and multiple receivers on the bus.

RS485 is two way: multiple transceivers on the bus.

Both busses use two-wire differential signals with identical voltage levels.

From a hardware point of view it is possible to connect RS422 receivers to an RS485 bus. You cannot place an RS422 transmitter on an RS485 bus. In other words: with a RS422 receiver you can only listen to an RS485 bus.

RS485 is only the hardware standard and says nothing about transmission protocol, so keep that in mind.


To me, this seems to suggest that connecting your device's RS-485 output to a NMEA-0183 differential LISTENER should work. It should allow the NMEA-0183 device to see the RS-485 output; and if that output is in the NMEA-0183 data format, it should work.

If you don't get this outcome, check the baud rate configuration. There are only two baud rates in NMEA-0183: 4800 is standard and 38,400 is "high speed."

IndigoJon
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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby IndigoJon » Sun Jul 17, 2022 9:46 pm

So we know that we can get the NMEA 0183 MWV sentence INTO the USB port of the laptop using the little Letotech RS485/USB converter; if I could find a PC program that would see that incoming sentence and transmit it OUT on another USB port, I could connect the bare wire end of that USB cable to the AT10 and I'd be fine. Or would it work to connect the Type A male USB plug of the Letotech converter with a Female/Female USB connector to another USB Type A male cable and wire the opposite end of that to the AT10?

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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby jimh » Mon Jul 18, 2022 8:01 am

I don't think you are following me.

NMEA-0183 is RS-422.

Your device outputs RS-485.

The electrical signals are the same, but the RS-422 is a one-to-one connection and only works in one direction, transmitter to receiver.

RS-485 is many-to-many connection, all devices are transceivers, and it works in all directions.

In a special case, you CAN connect an RS-422 receiver to an RS-485 bus. This should work.

But you cannot connect an RS-422 transmitter to an RS-485 bus. That won't work.

This means that your device, with its RS-485 output, should be able to be successfully connected to an RS-422 input.

The protocol convertor device you have should have an RS-422 input.

WHAT YOU SHOULD DO:

Connect your device's RS-485 input/output port to the protocol convertor's RS-422 input.

You will wire the RS-485 DATA A to the RS-422 LISTENER A or input A or input (+)
You will wire the RS-485 DATA B to the RS-422 LISTENER B or input B or input (-)

This is my best suggestion.

You should be able to also wire in parallel the RS-485-to-USB convertor and still see the data being sent from the device.

To test this, go back to the set up you have that works, the device to the RS-485-to-USB convertor. Get that working again. Then connect the protocol convertor in parallel. If the data is still visible on your computer, that means the addition of the protocol convertor did not harm the output.

IndigoJon
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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby IndigoJon » Tue Jul 19, 2022 6:55 pm

I think I am going to need an RS485 to RS422 converter. A company called SerialComm makes a convertor. An RS485 (2-wire) input then converted to RS422 (4-wire). I have ordered this model:

https://www.serialcomm.com/serial_rs232 ... _info.aspx

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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby jimh » Wed Jul 20, 2022 9:11 am

I looked at that convertor, but I don't think you really need it. You only need to get data from RS-485 to RS-422, and not the other way around. I already described how you could do that without an $80 convertor. However, the electrical convertor should achieve what you want: to get data sent in RS-485 signals to become an RS-422 signal.

Did you test the method of connecting the RS-485 bus to a NMEA-0183 LISTENER? For that direction, I don't think you need the convertor.

IndigoJon
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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby IndigoJon » Wed Jul 20, 2022 1:43 pm

In a previous post you wondered: "Whether RS-485 can be directly connected to NMEA-0183 is unknown to me." It
is appearing that the answer is that it can't be. That's why I ordered the converter.

I have reset the baud rate of the Calypso to 4800, and the software confirmed that the configuration with that rate had been successful. Then I connected the Calypso to the RS485/USB converter, plugged into the laptop, and could see MWV sentences streaming to NMEA Reader.

Immediately, I connected the Calypso according to your most-recent instructions to the AT10, and—nothing. The AT10 supports the MWV sentence, so it must not like the data coming directly from the Calypso.

I'm hoping the converter will do the job. Fingers crossed.

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Re: RS485/NMEA0183 Connection to Simrad AT10

Postby jimh » Fri Jul 22, 2022 11:01 pm

Thanks for the follow up on testing a direct connection.