Receiving NMEA Data over UDP
Receiving NMEA Data over UDP
August 06, 2018 07:04AM
Good Morning,

I have installed Polay Navy on a Mac Mini (running on OSX 10.13.6). I'm currently trying to recieve NMEA data via an NPort IA-5150I (using UDP) over our ships network.

Although I can see the data coming in via the Polar Navy NMEA console, i'm not sure that the Nport configuration is set correctly (see attached pictures).

I also have an iPad runing the iSailor software which does successfully receive NMEA data from the same NPort source, although I suspect that there are errors present in the stream (the GPS and AIS data constantly drops out).

Can anyone advise what settings need to be changed on the NPort to improve the data being streamed?

I have also attached a screenshot of the serial settings that we're using on the Nport for reference.

Thanks in advance!
open | download - Screen Shot 2018-08-06 at 10.26.07 AM.png (330.4 KB)
open | download - NMEA Receiving.PNG (28.8 KB)
open | download - NMEA Sender.PNG (39 KB)
Re: Receiving NMEA Data over UDP
August 07, 2018 04:53PM
So I changed the packet length to 82, and starting to recieve data. Unfortunately its still dropping out (see attachment).

I see that the input is a 38.4 K Baud, so I assume that the NMEA data is in 0183-HS.

Polar Navy is compatible with NMEA 0183-HS? I see no mention of it in the specs.
open | download - Screen Shot 2018-08-07 at 8.38.08 PM.png (275.4 KB)
Re: Receiving NMEA Data over UDP
August 09, 2018 09:14AM
NMEA delivered over UDP does not have a concept of "baud rate", as it is not a serial connection. In practical terms, NMEA over UDP is not a standard either, but rather a "common sense" application that is often supported by various vendors in an informal manner.

From the screen capture it appears that many of the NMEA messages are split into several pieces (i.e. a single NMEA sentence appears over the course of several lines).
When sent over UDP, a single UDP packet should carry a single complete NMEA message. If your UDP data source breaks messages into multiple UDP packets, NMEA data may be corrupted. You may want to try increasing an NMEA packet size (try 100 or above).
Barring that, you may want to see if your NMEA sender supports use of TCP connections, which do not have any specific requirements on individual packet data.

Polar Navy Support
Re: Receiving NMEA Data over UDP
August 09, 2018 03:56PM
Reconfigured for TCP and we have a steady data connection.

Thanks again for your help.
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