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Greg A.
Greg A., Engineer
Category: Marine Electronics
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Experience:  Engineer / Consultant
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I am trying to connect Garmin 556 to Lowrance Link5 VHF.

Customer Question

Hi I am trying to connect Garmin 556 to Lowrance Link5 VHF. I have all cables supplied in boxes . Am I right in thinking Blue from GPS to Yellow NMEA in + on Radio then Brown from GPS to Orange NMEA out + to radio, I understand power + and - This will just leave Black NMEA -,Green NMEA -, blue,grey and clear not used on the radio lead._
Submitted: 2 years ago.
Category: Marine Electronics
Expert:  Pete replied 2 years ago.
Hi Richard,
The Lowrance wiring is:
Brown to Orange GPS (+)
Blue to Yellow GPS (+)
Green from GPS to DSC (-)
Black to Ground
Customer: replied 2 years ago.
Hi, Ok so here is what I have, this is all new just out of the box,Lowrance cable has the following colours with tags,
Yellow NMEA in (+), Orange NMEA out(+) Green MNEA in (-) Black NMEA out (-) Blue,grey and clear (3 wires) not tagged.
Now the Lowrance book shows : Orange to GPS, Green from GPS, Black to ground, Blue and Grey no connection (not used), Clear program/clone (not used).
The wiring from the GPS is : ( this is shown in booklet as )
Red power (obvious),
Black Ground (power and MNEA0183),
Blue NMEA 0183 port1 Tx (out),
Brown MNEA 0183 port 1 Rx (in),
Grey NMEA 0183 port 2 Tx (out),
Violet NMEA 0183 port 2 Rx (in), Green CANet L (if applicable),
White CANet H (if applicable), Orange Accessory on, Yellow Alarm Low.
So you have suggested: Brown from the Radio (Ihave no Brown) to connect to the Orange, (accessory) on the GPS,
The Blue from the Radio (not used), to be connected to the yellow (Alarm low ) on the GPS,
The Green CANet L (if applicable) From the GPS connected to DSC (-), I do not have this or know what colour DSC is,
Black to Ground, I assume from both units. Then all other wires are not used. This will work ?Richard
Customer: replied 2 years ago.
Can you please read my reply above and answer the question.Thank You
Expert:  Greg A. replied 2 years ago.
Hi Richard,
I see that the other expert has opened your question for other input, so perhaps I can help.
First, I understand your confusion, as wiring, color codes, and signal labels/names are ***** ***** consistent in the industries involved here (GPS units, Marine radios, etc.) AND between manufacturers.
Plus there are two (slightly) DIFFERENT ways to transfer this NMEA "data" when using a serial connection - namely "Single Ended" (with a single signal references to "ground") and "Differential" (where TWO signals are used - normally labeled with + (plus) and - (minus).
So when I looked at the Installation Guide for the GPSMAP 500 series devices (link to that guide below), and looked at pages 6 & 7, I will use the connection diagram on the top of page 7 as a reference.
By the way, here is a link to the Lowrance Link-5 VHF radio if you need to look at it. Of particular interest is page 50, which is the Wiring for the GPS/COM connector.
Now the FIRST thing to note about the Garmin device is that it is using the "Single Ended" transmission and reception method, and that usually "works just fine" in a SMALL wiring system such as found on a vessel.
So we will say that the Lowrance Radio system is the "NMEA 0183 compliant device" that is shown on the right-hand side of that diagram (top of page 7 of the Garmin Installation Guide).
But as you may have noticed from the Lowrance documents (or tags on the wires), is that this radio uses the "Differential" method to transfer data (notice the + & - signs on the signals). But DON'T WORRY - we CAN get this to work. What we will basically do is use ONLY the + (plus) signals from the Lowrance radio, while paying special attention to the - (minus) signals (mostly tied to ground at a RECEIVER - OR - left open at a TRANSMITTER).
Hopefully this will all make sense soon, and will work once connected AND configured properly on each device.
So let me give you a "table" for what I believe should be the correct connections of these two devices, dealing ONLY with the wires we need to connect for DATA (use the power and ground from the reference diagram).
GPSMAP 500 series --------- Lowrance Radio ---------
COLOR - function Direction COLOR - function Direction
Blue - NMEA port 1 Tx (out) Yellow - NMEA IN (+) (in)
----- - ------------ Green - NMEA IN (-) (Ground)
Brown - NMEA port 1 Rx (in) Orange - NMEA OUT (+) (out)
Black - Ground (pwr & NMEA) Black - NMEA OUT (-) (float - no connection)
Now notice that the GROUND - for the power system AND the NMEA system are both connected at a common point - on both devices in the diagram and both sets of documents, so MOST of the "translation" from differential to single-ended is already done for us - and using ONLY the PLUS side of the signals should be fine for what we want to do.
Now I have one other reference for you, which is an article about the NMEA 0183 "standards" and making the interconnect between different devices that "claim" to be compliant. Like MANY standards, they DEFINE the TERMS that SHOULD be used in the industry, but also give a "translation" of the signal names that manufacturers may use and the standards name. See the FIRST table in the following article.
Now IF you want to read all the details from that article, please feel free to do so. But what I have done below is taken one of the tables in that article and "mapped" the two different devices you are using into that table, and came up with the table below.
The table in the article is labeled "GX1500S and HDS-8 single-ended mode", with the GX1500S device on the LEFT of the table, and the HDS-8 (single-ended) on the RIGHT. And you SHOULD notice that the article table has two BLANK lines - where the HDS is used (because it is single-ended).
So what I have done below is try to make that SAME table, except I put the colors and wires in that the Lowrance Link-5 and the GPSMAP 5xx are using, but keeping the NMEA NAMES in place.
LOWRANCE LINK-5 and GPSMAP 500 single-ended mode
LINK-5. . . . . . . . . . . . . . . . . GPSMAP 5xx series
Color . .NMEA Name . . . Connection . . NMEA Name . . Color
BLACK . .TALKER B . . . (floats) . . . . . . . . . . . . .
I know this is all very "technical", but hopefully it makes enough sense for you to connect the wires correctly, and to get the two devices "talking" to each other.
And one other NOTE about that (devices "talking") - EACH device needs to be checked for its "Baud Rate" - on the communication port. MOST devices are set to 4800 Baud by default, but it never hurts to CHECK and make sure.
One last note: While looking this stuff up, I ran across the following site about "DSC" (Digital Selective Calling), and the site includes the WHAT, WHY, and HOW of the DSC system and radios. You may want to take a quick look to make sure everything is working - once you have these connections made and can TEST the functions.
Please let me know your results or if you have more questions.
Best Regards & Stay Safe on the Water, Greg A.
EDIT: It looks like the EDITOR here has messed up my "tables", making them unclear. So I will try to make a simple diagram and may be able to post it here - WHEN you reply.