HDS7 Gen3 to Link-5 Communication

[nadol]

Hi all. To be honest I am glad to be here--no Idea how I got here as I live in Poland.

I am looking for solution how to connect properly my Lowrance HDS-7 Gen-3 with Link-5 VHF radio to get GPS position for the DSC. I tried to contact Lowrance help desk, but their answers are not quite useful. I would be grateful for any tips what is done wrong in my set.
OK shall I begin:

I connected wires (at first) like this:

HDS             VHF radio
yellow TX+      yellow NMEA IN+
blue TX-        green NMEA IN-
orange RX+      orange NMEA OUT+
green RX-       black-orange NMEA OUT-

Then Lawrance advised to do like this and right now it's only connected:
--Yellow to Yellow
--Blue to Green
and the rest of wires are not connected.

Baudrate is set to 4800. HDS gets proper GPS position but does not transfer to VHF radio. What can be the problem? Please advise.

Additionally below you can find link to photos I have taken of the devices and its settings:

https://drive.google.com/folderview?id= ... sp=sharing

Thank you in advance,
Greg

[jimh]

Hello NADOL. Let's see if I can help you with this problem of interconnecting two devices using NMEA-0183. The problems you are having are very common problems. They result from lack of compliance by the manufacturer in maintaining consist use of nomenclature and wire color coding.

INTERCONNECTING NMEA-0183 DEVICES

FIRST STEP: IDENTIFY SIGNALS

The initial step in making an NMEA-0183 interconnection between devices is to identify the signals available. Usually these signals are provided on a loose fan out of wires with various colors of wire insulation. The signals can only be identified by correlating the wire color to to the wire signal or function.

NADOL has provided some data about wire color and wire signal and function, but I must double check that. I have to get the data from a primary source. I turn to Lowrance literature. First I look for the HDS-7 Gen-3, I will use this document:

http://www.lowrance.com/Root/Lowrance-D ... -001_w.pdf

I turn to page 26, and see the diagram showing the wiring fan out that identifies the signal function by wire insulation color. That shows:

NMEA TX A = Yellow
NMEA TX B = Blue
NMEA RX A = Orange
NMEA RX B = Green

These descriptions are almost at the standard usage of names. I would prefer to describe them according to the standard names, as follows

HDS-7 CHART PLOTTER SIGNALS
TALKER A = Yellow
TALKER B = Blue
LISTENER A = Orange
LISTENER B = Green

Now I have to find the LINK-5 radio literature. I turn to Lowrance again, and find:

http://www.lowrance.com/Root/Lowrance-D ... -001_w.pdf

In that document I find on page 50 a diagram that again shows signal function by wire insulation color for the wiring fan out. That shows:

NMEA OUT (+) = Orange
NMEA OUT (-) = Black
NMEA IN (+) = Yellow
NMEA IN (-) = Green

Again, these names are not the standard names, so I immediately have to translate them

LINK-5 RADIO SIGNALS
TALKER A = Orange
TALKER B = Black
LISTENER A = Yellow
LISTENER B = Green

Now that we have both devices with their signal names in the standard form, it is very easy to determine how to interconnect them. We see that all devices have both a TALKER A and B and a LISTENER A and B. We use the basic rule:

Connect TALKER A to LISTENER A and TALKER B to LISTENER B

Now we can make the proper physical (and electrical connections) between the devices. We will have the following two circuits:

HDS-7 talking to LINK-5
TALKER A (Yellow) to LISTENER A (Yellow)
TALKER B (Blue) to LISTENER B (Green)

LINK-5 talking to HDS-7
TALKER A (orange) to LISTENER A (Orange)
TALKER B (Black) to LISTENER B (Green)

I hope I don't confuse you by switching the order of the HDS and LINK in the second list, but I want to show that circuit as originating with the lINK-5 and going to the HDS-7, that is, TALKER to LISTENER. Here are those interconnections again, perhaps easier to understand, as I will keep HDS-7 on the left and LINK-5 on the right:

HDS-7                LINK-5
TALKER A (Yellow) to LISTENER A (Yellow)
TALKER B (Blue)   to LISTENER B (Green)

LISTENER A (Orange) from TALKER A (Orange)
LISTENER B (Green)  from TALKER B (Black)

Now we compare my wiring design with NADOL's first approach: they are almost the same, except for that "black-orange" confusion. As for advice from Lowrance, I have no idea where the first-tier technical support at Lowrance came up with their advice. I will ignore it.

If the documentation from Lowrance is correct, then the wiring should be just as I describe above. There is no doubt that is how it should be, according to NMEA. The only concern is for the accuracy of the documentation. Let us assume the documentation is accurate. So we will go with that wiring. We now have the physical layer finished.

In the next article, we will look for other settings in the data layers.

[jimh]

INTERCONNECTING NMEA-0183 DEVICES

SECOND STEP: FINDING COMMON SIGNALS

Now that the two NMEA-0183 devices are connected, we must make sure they will have common settings to permit the communication to take place over the electrical interface. There are two elements to consider: the signal rate and the data contained in the signals.

Baud Rate
Now that we have made the correct physical and electrical connection between the two NMEA-0183 devices, we look for other settings that need to be made. The first setting that might affect communication is the signal rate or baud rate of the signals. Since these signals are just standard NMEA-0183 signals, they should be signaling at 4800 baud. NADOL mentions he has set the baud rate to 4800 for the HDS-7. This is correct. We should have both TALKER and LISTENER set to the same baud rate, and they should communicate their data.

Data to be Exchanged
The next layer to examine is the actual data that each device will send to the other device. We can only communicate between devices if both devices speak the same language. That language is NMEA-0183, but there are many words or sentence in NMEA-0183. Not every device knows every word or sentence. We will be limited to only the words or sentences the two devices have in common. Again, we turn to the documentation. We have to find documentation that lists these NMEA words or sentences, and find ones in common that can carry the data we want to communicate.

The most elementary part of this interconnection is to get the boat's position data from the chart plotter to the radio. We look at the radio documentation to see what NMEA sentence is would like to get. This information is found on page 52 of the radio literature. It says:

GPS data sentences can be received: RMC, GGA, GLL, GNS

Those three-letter groups are acronyms for data parameters which are called NMEA-0183 sentences. We need to set the chart plotter so it sends at least one of the sentences. We do not need to make any setting change on the LINK-5 radio, as it is going to be already set to listen for any of those sentences without needing further configuration. The LINK-5 radio knows all those sentences, and it is always listening for them. This is typical of a LISTENER. It is listening for any sentence is knows, and it does not need to be configured to look for just a specific sentence.

Now we turn to the chart plotter documentation (see link above) to find the sentences the HDS-7 can send. We find this information on page 61 in a table of "NMEA 0183 supported sentences." The table lists all the sentences that can be sent. We see that the chart plotter can send a great many sentences, including GGA, GLL, and RMC. So we have three common sentences, GGA, GLL, and RMC, that the chart plotter and send and the radio can understand.

Next we have to configure the TALKER, the chart plotter, to make sure it will send GGA, GLL, and RMC. There is no harm in sending all three. They all contain the position data. The difference among them is what other data is included. (You can find details about NMEA-0183 sentences at the website http://freenmea.net/docs.) I will explain that next step in the next article. The simplest approach is to configure the chart plotter to send RMC. That will give the radio all the data it needs.

[jimh]

INTERCONNECTING NMEA-0183 DEVICES

THIRD STEP: CONFIGURING TALKER

To set the Lowrance HDS7 to send certain data, it must be configured manually. I don't know what the default settings are. The best approach is to not trust in the default settings. Make the settings manually.

NADOL shows the location in the user interface on the HDS7 where these settings are made in his image at

https://drive.google.com/folderview?id=0B7dXC2lgN5XQdmtlcS1nYm1jazg&usp=sharing

in the image denoted as Image 3 of 8. (I cannot link directly to it.)

But that image does not show us if NADOL has properly configured the chart plotter. My recommendation to NADOL is:

--return to the configuration page you show in the image (linked above)

--expand the listing to show the details hidden under each category

--set the chart plotter to send the proper sentences to the radio, that is, to send GGA, GLL, or RMC, or all of them. You find GGA and GLL under the GPS heading. You will find RMC under the NAVIGATION heading. I suggest sending RMC as it will contain all the data.

Let's stop at this point and wait for NADOL to return. NADOL must perform the recommended actions I have given him:

--change the interconnection wiring as I describe. This can go faster if just a temporary connect between the signal wires is made; don't use a connector. It is faster to test if you just make a quick connection. When everything is working you can go back to using a connector arrangement;

--change the settings on the chart plotter so it will send the desired sentences;

--check on the radio to confirm the two devices are communicating; and

--report the outcome.

If we get to that point, we can continue to discuss the interconnection and work on getting the radio to send data to the chart plotter. If we don't have success, we can try other approaches to resolve the problem. I am standing by for NADOL to reply.

[jimh]

INTERCONNECTING NMEA-0183 DEVICES

FOURTH STEP: CONFIGURING RADIO TO TALK TO CHART PLOTTER

I am jumping ahead because I think NADOL has actually got the chart plotter talking to the radio. Now we want the radio to send to the chart plotter. The wiring necessary is given above in my first step instructions.

I think this is where NADOL is struck, because he has only a one-way communication wired between the chart plotter (as TALKER) and the radio (as LISTENER). I show that wiring above. When completely wired, we have two-way communication on two separate circuits, one in each direction. Therefore we need to make a second path, with the radio as TALKER and the chart plotter as listener. See my wiring advice to implement this second path.

Since the baud rate adjustment on the chart plotter is properly set, there should not be much to do. We now turn to see what data the radio can send to the chart plotter. This is an important second phase of connecting the radio and chart plotter.

A DSC radio can send data to a chart plotter based on radio transmissions it receives via digital selective calling methods. We turn to the LINK-5 radio documentation to see what it has to say about NMEA-0183 output. Again page 52 we see:

NMEA output sentences: DSC (for DSC call), DSE (for enhanced position).

In the case of this radio, I do not believe there is any sort of configuration necessary. It only knows two sentences to send, and it will only send them if it receives a DSC message containing that data. So the radio is ready to send these two sentence, and no configuration necessary. There is one option for the COMM PORT, shown on page 22 of the manual: NMEA CHECKSUM. This options refers to how the radio will send data. Usually data is sent with a checksum character at the end of the packet. The default in the LINK-5 radio for NMEA CHECKSUM is to be set to ON. I recommend leaving it at that setting.

An article about NMEA-0183 at Wikipedia says the checksum is optional on most NMEA-0183 sentences; it is only compulsory on a few, including RMC. But this is contradicted by other sources, such as Eric Raymond's excellent website, NMEA Revealed, which indicates the checksum is mandatory. I suspect that in many implementations of NMEA-0183 the LISTENER may ignore the checksum, if one is sent. Because the data is being sent only a short distance on a wired connection, it is unlikely that the data transmission itself would create errors in the data, and ignoring the checksum is probably unlikely to result in a problem. However, the option to send or not send the checksum creates one more variable. I do not recall seeing this option in most NMEA devices, and therefore I would leave it set to NMEA CHECKSUM ON.

Note also that the LINK-5 appears have the COMM PORT speed fixed at 4800 baud. No adjustment needed there, that is the standard rate.

Now we turn to the chart plotter to see if NMEA sentences DSC and DSE are in its vocabulary. Using the documentation (linked above) we again look on page 61 to see if these sentences are supported by the HDS-7. Under the table heading AIS/DSC, we find the chart plotter can receive DSC and DSE. That is good news. We now know that the radio and chart both understand DSC and DSE sentences. When they are properly wired together, the chart plotter should respond to data from the radio.

Exactly what the chart plotter will do when a DSC radio sends it data from a digital selective call received on the attached radio is not exactly set in stone. Typically the chart plotter will respond to input from the radio by providing some sort of presentation on the electronic chart. I have actually explored this behavior is some detail. Rather than repeat my findings here, please see my lengthy article about digital selective calling at

Chart Plotter Interface in Digital Selective Calling
http://continuouswave.com/whaler/reference/DSC_ChartPlotter.html

When interconnecting a chart plotter to a radio for this function, there is no simple way to test if the connection is working. The only way to test is to send a digital selective call to the radio from another DSC radio. You need a second station to help you in testing, or you need to have to radio at your test location. The simplest test is to send a DSC request from your radio to the second radio asking for the position of the other vessel. That vessel should respond with a reply DSC call--if working properly--and send your radio their position. Your radio--if all is connected properly--will send that data to your chart plotter. And your chart plotter--if working correctly--should plot the position of the other vessel. The only way to determine if this works is by testing the entire system. Make a DSC call to the other radio, get a response, and see what the chart plotter will do. There are several chances for this test to break down, other than in your wired connections. For that reason, test with a second radio that is known to work properly with DSC calls. That will take some of the other places for failure out of the test system.

[nadol]

Hi All,
Thank you all for so many information :)

OK - I checked the setting on HDS (please reffer to photos) but it seems all functions are already switched on.
https://drive.google.com/folderview?id= ... sp=sharing

To be honest I am starting to think some part may be damaged (wire, deviced itself)...

[jimh]

The output of a NMEA-0183 TALKER can be checked by using a computer. If you have a serial port on you computer, or perhaps a USB-to-serial-port adaptor, connect the NMEA-0183 output of a TALKER like the HDS-7 and see what it is sending. Run a terminal application and monitor the serial port input. You should see the data output. In this way you can confirm that a TALKER is sending data.

From the screen images, it certainly looks like the HDS-7 is configured to send the sentence RMC. However, the chart plotter won't be sending any data until its GNSS receiver has acquired a position fix. Are you getting a position fix on the HDS-7?

[jimh]

Also for NADOL: if you suspect either the chart plotter or radio of having a defect, the LINK-5 radio may be more likely to be the problem. Lowrance seems to have very good results with their chart plotters, but the LINK radio line has shown some problems.

[nadol]

To be honest - Link-5 is completely new, HDS as new. The HDS gets proper fix, still GPS position; no problems with that.

[jimh]

If the two NMEA-0183 interfaces of the devices are corrected wired together, if the two devices are correctly configured, and if the two devices are working properly, it is hard to find a cause for the interconnection to fail to work.

In a test environment in which there is a TALKER and a LISTENER, and there is no test equipment available to investigate the signals in any way, the only alternative method of diagnosis is to substitute a new devices for each of the two devices to see if there is a change in behavior of the system.