Moderated Discussion Areas
ContinuousWave: Small Boat Electrical
NMEA-0183: SIMRAD NSS-8 to ICOM-504A
|Author||Topic: NMEA-0183: SIMRAD NSS-8 to ICOM-504A|
posted 04-30-2012 09:53 AM ET (US)
Here is my NMEA 0183 connectivity between my Simrad NSS8 and ICOM 504A. It conforms with the RS422 convention as displayed in Simrad's Installation Guide.
Picture of my ICOM 504a install and associated NMEA 0183 connectivity to my Simrad NSS8.
To receive GPS input from the Simrad to the ICOM
Simrad blue (ground) to Icom Shield/Ground Wire
Simrad Yellow (Transmit) to ICOM red (Receive)
Simrad orange (ground) to ICOM shield/ground wire
Simrad Green (Receive) to ICOM white (transmit)
posted 04-30-2012 09:00 PM ET (US)
Tom--I don't think your installation is quite proper. If the interface is set up as an RS-422 with differential inputs and outputs, you should not tie an active output to ground, as you have shown with the TX- being grounded. You can let the TX- fload, it the differential is referenced to ground. I don't mean to say your wiring does not work, but just that an active output should never be tied directly to ground. Perhaps you've set it to RS-232 or single ended. In that mode the other transmit conductor is (perhaps marked TX-) is probably just a ground, not an active output.
posted 04-30-2012 09:41 PM ET (US)
Problem is when connected as you recommend it doesn't work. Spent 2 hours on the line with Simrad discussing the issue. Simrad told me the RS232 setting will not work in my application.
posted 04-30-2012 11:38 PM ET (US)
Tom--I don't have a SIMRAD NSS or a GX2150 to experiment with, so I just go with what SIMRAD says and what Standard-Horizon says, and with what I know about electronics.
Since there are no schematic diagrams to look at to see exactly what sort of circuitry is being used in the serial communication ports, it is impossible to tell if the circuit marked as an active output is really an active output. It is possible that the output is also not referenced at all to ground, and if you don't connect one side of the output to ground it won't work.
This is all part of the problem that has evolved with NMEA-0183. Manufacturers have been able to produce equipment that is supposed to be compliant with the NMEA-0183 standard, yet there are no standards of compliance--apparently.
I can't say for certain what the NMEA-0183 standard actually says because NMEA keeps it a secret and only reveals it to people who purchase the standard. And, even if I purchased the standard, I could not tell you what is in it because it cannot be disclosed. It is the craziest "standard" I ever heard of.
Frankly, I have become fed up with trying to help people interface marine electronics according to the NMEA-0183 standard for these reasons:
--the standard is a big secret and I can't get any information on it from NMEA
--NMEA does absolutely nothing to help people with these problems; there is no website, no presence in discussion groups, no email help, no FAQs, really nothing at all from them. If you call them they want you to join or buy information.
--the manufacturers all implement the physical layers of the standard in a completely uncoordinated manner. They use different names for the signals, they use different colors for the wires, they use different types of receive and transmit circuits--sometimes even in one piece of gear!
It seems to me that the more people who are not associated with NMEA try to help regular boaters figure out how to connect marine electronics using NMEA standards, the more we are working for free on behalf of NMEA. Maybe NMEA can pick up some of the load. They have offices, staff, employees, and--most important--they have the knowledge of the standard. It ought to be simple as pie for NMEA to tell someone how to interconnect two pieces of marine electronics that are sold as being NMEA compliant. Why don't they start doing this?
posted 05-01-2012 08:33 AM ET (US)
Jim, I agree. They've taken something that could be so simple if there was a standard and made it into a spaghetti western. Makes no sense what so ever. Sad thing is these is no relief in site.
posted 03-22-2014 11:16 PM ET (US)
I have separated this article from another thread.
I believe the problem in this interface of Simrad and Icom is two-fold:
--Simrad has sent out an errata sheet for this model that correct the color coding of the wires; it is not clear which color code applies for this particular case.
--an active differential NMEA (sometimes referred to as RS-422) TALKER port should not have the TALKER B grounded. The TALKER B is sometimes called the TX- or Tx- or otherwise designated with a minus sign. These minus and plus signs associated with differential serial data signals are not polarities.
The differential signal marked with a plus is the non-inverted data; the differential signal marked with a minus is the logical-opposite of the other signal, or the inverted signal. But they are both active signals, and active signals should never be connected to ground.
If you have a SIMRAD NSE or NSS series, you should check with SIMRAD to get the proper wiring color codes and identify the signals for your particular unit.
There is also a further complication in with SIMRAD (and with Lowrance) in their serial data signals: they can be switch between modes, and can be either in NMEA (RS422, also called differential) and non-NMEA (RS-232, also called single-ended) modes. The interface depends greatly on how you have set the mode.
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.