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Author Topic:   Wiring NMEA-2000 Network with Mixed Old and New Devices
acseatsri posted 12-21-2013 04:50 PM ET (US)   Profile for acseatsri   Send Email to acseatsri  
I have an older Lowrance GPS with a blue network, A new Lowrance GPS (in need of networking) and also a new Honda with the red network. I'd like to tie and use everything together and share info across both units, the older unit as a back-up. Is this possible, and what additional fittings do I need?

jimh posted 12-22-2013 10:08 AM ET (US)     Profile for jimh  Send Email to jimh     
Devices which are certified as NMEA-2000 devices can be connected to a NMEA-2000 network without causing a problem to the network, even if those devices have wiring components that cannot be directly plugged together. You just have to accommodate the differences in the wiring devices, but the networking remains compatible. As for whether or not the older devices will interoperate in the same way that newer devices will, the interoperation depends on the software in the devices, and if that software allows for the interoperation you desire, such as sharing of data between devices.

The association of the colors red and blue with wiring devices for NMEA-2000 networks is only used by Lowrance. The devices they call red are now actually no longer red but black. These devices are ones that use the DeviceNET connector, which is more or less the present standard connector for wiring NMEA-2000 networks. The devices that Lowrance calls blue are their own style of connector used only by them for NMEA-2000 in earlier implementations. (I actually like those old blue connectors because they have a bayonet type retaining collar instead of a threaded collar.) There really is no term "red network" except as created and used by Lowrance. The devices that Lowrance once called "red network" are DeviceNET connectors.

It seems that back a few years ago NMEA (the organization) did not really enforce a standard connector for the NMEA-2000 network wiring, and, even today, there are variations. For example, Raymarine is using their own style of connector for their network, which they have branded as SeaTalkNG. But at the present, most manufacturers are making devices with DeviceNET connectors.

If you have a legacy device with a Lowrance blue network connector and a legacy network already in place with blue connectors, I suggest the following:

--segment the network wiring into two distinct segments, one using the old blue devices and one using the new DeviceNET devices;

--buy (if you can still find one) a Lowrance adaptor cable with a blue connector on one end and a red connector on the other end, or, make your own such cable by splicing together an old cable and a new cable;

--the new cable you bought or made will be used to connect the two segments of the network backbone; and,

--plan to connect new devices you will add to the network to the DeviceNET segment, and leave the legacy devices connected to the old Lowrance blue connector network.

If you only have one legacy device with a Lowrance blue connector, I suggest the following approach as a better method to combine old and new:

--create a new network backbone with all power, T-connectors, and terminators using the new DeviceNET wiring;

--connect all the new devices to the network with their DeviceNET connectors;

--make (or buy) one specialized drop cable with a DeviceNET connector at the network end and a Lowrance blue connector at the device end, and use this to connect the lone legacy device;

--sell off the old blue network wiring devices to someone who is looking for them to support their older network. (These blue wiring devices are getting hard to find now, and you might be able to sell them for a decent price.)

jimh posted 12-22-2013 10:19 AM ET (US)     Profile for jimh  Send Email to jimh     
How to make a network extension cable with different connectors

To make your own adaptor cable for wiring between segments of a network that uses two types of connectors, you need to make a cable with a connector of one type on one end and a connector of the second type on the other end. Usually in NMEA-2000 wiring the extension cables will have connectors of different gender on each end. This allows for the network cables and devices to be daisy-chained together. When making an adaptor cable you should follow this pattern, that is, have a plug connector on one end and a socket connector on the other end.

In NMEA-2000 cables there is a practically universal color coding of the conductor insulation that follows this pattern:

--Red is the network power positive circuit

--Black is the network power negative circuit

--White is the network signal HI circuit

--Blue is the network signal LO circuit

--Shield or drain is the network ground circuit

If you want to make a custom cable, you can typically just cut two existing cables, one of each connector type, in half. Then take one half of each type cable and connect it to one half of the other type, observing the gender alternation recommended above. The wiring will just be color-to-color, that is, red to red, black to black, and so on.

You do not have to fuss or worry about the shield at the splice enwrapping the inner conductors. Just splice the shield as its own circuit. It is generally easier to make these splices if you do not try to make them in-line.

acseatsri posted 12-22-2013 05:49 PM ET (US)     Profile for acseatsri  Send Email to acseatsri     
If I have a 4-place combination Tee (instead of 4 individual Tee's), do all of the outlets have to be used?

The other surprise I just had is that the internal antenna in the new GPS doesn't work where I have the unit mounted in the dash. The older unit has an LGC2000 antenna connected to the network. Will the new unit accept position data from the older unit's antenna?

tmann45 posted 12-23-2013 07:23 PM ET (US)     Profile for tmann45  Send Email to tmann45     
If I have a 4-place combination Tee (instead of 4 individual Tee's), do all of the outlets have to be used?
No, they do not.

The other surprise I just had is that the internal antenna in the new GPS doesn't work where I have the unit mounted in the dash.

What is the GPS unit with the internal antenna that will not work?

jimh posted 12-23-2013 07:25 PM ET (US)     Profile for jimh  Send Email to jimh     
If you have a wiring device with positions for four drop cables to connect, it can be used with less than four devices connected. The only concern is to protect the unused sockets of the four-position device from getting wet or allowing dirt to enter. I don't know of any DeviceNET blank connectors. You may have to use electrical tape to cover the unused connectors.

The GPS receiver in your new device appears on the network as a separate device from the chart plotter display. In the Lowrance configuration menu you should find an option to select the source for a GPS receiver on the network. If you have an HDS series device, this option is usually found in the Settings menu, in the Network submenu, in the Data Sources submenu. See my hypertext document for more information on how to select data sources on a Lowrance HDS device:

All the GPS receivers on a NMEA-2000 are just sending their data to the network, not to any specific destination on the network. The GPS receivers just send their data, and they do not know who is going to use it. You can configure any device on the network to use the data from any of the GPS receivers. If you want to use the GPS receiver in your LGC2000 as the data source for "new" Lowrance--and, by the way, you have never mentioned what model of Lowrance chart plotter and SONAR device you have so we don't know what sort of device you are asking about--then you just have to configure that device to use the LGC2000 receiver data.

The LGC2000 is not an "antenna" but it is an external GPS receiver with its own NMEA-2000 network interface. There are other devices which are actually external antennas for GPS receivers, but the LGC2000 is not one of them. It is a complete receiver, coupled to a NMEA-2000 network interface. An external antenna is just an antenna. It is not a receiver. It does not have a NMEA-2000 interface. An external antenna would connect by some cable, usually a small diameter coaxial cable, to its associated GPS receiver. This is nothing like the NMEA-2000 connnection used for the Lowrance LGC-2000 GPS receiver with NMEA-2000 network interface.

Hoosier posted 12-25-2013 12:14 PM ET (US)     Profile for Hoosier  Send Email to Hoosier     
I think any unused port on a multiport hub needs to have a terminating resistor.
tmann45 posted 12-25-2013 07:06 PM ET (US)     Profile for tmann45  Send Email to tmann45     
I think any unused port on a multiport hub needs to have a terminating resistor.

No, that is incorrect, only the ends of the backbone need a terminating resistor. That means only two resistors, one on each end of the backbone.
acseatsri posted 12-26-2013 10:05 AM ET (US)     Profile for acseatsri  Send Email to acseatsri     
The units I have are a new Lowrance HDS12 Gen2 Touch and an older Lowrance LCX-110C. The built-in antenna in the new unit is not working with the HDS12 mounted in the dash.
dfmcintyre posted 12-26-2013 11:39 AM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
Regarding the new internal not working when mounted in dash:

- Did it work prior to mounting it in the dash?

- And, is the dash more vertical or with any sort of obstruction (like a metal sun shield, for example) between the unit and the sky?

I'm considering picking up two Gen2's for two different vessels, and this discussion is interesting, as I plan on dash mounting both.

Regards - Don

acseatsri posted 12-26-2013 04:32 PM ET (US)     Profile for acseatsri  Send Email to acseatsri     
The built-in antenna [in the Lowrance HDS-12 Gen2 Touch] is working now. I had to let the unit discover what was connected and configure itself.

I think I'm going to just hook up the [Lowrance HDS-12 Gen2 Touch] to the network and use the older [Lowrance LCX-110C] exclusively as a back-up. If I connect the older [Lowrance LCX-110C] to the network, the LGC2000 GPS receiver wouldn't work unless I power the network from the GPS side, which would mean the the Honda gauges would also always be on if the unit was powered on.

jimh posted 12-28-2013 11:03 AM ET (US)     Profile for jimh  Send Email to jimh     
I think you are making reference to the arrangement in some older Lowrance devices that had NMEA-2000 connections for the device itself to provide power to the NMEA-2000 network. As you mention, having network power come from an individual device can be a problem in network powering. One way to overcome this problem is to separate the network backbone into two segments for power. One segment of the NMEA-2000 network can be powered from one source, and another segment of that same network can be powered by a difference source. Briefly, you can accomplish this by using a power isolation device in the network backbone wiring, by using a power-T connector that has separate circuits, or by modifying a standard network-T so that the power circuit is broken. For more detail on network power in segments, see

NMEA Network Power

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