New feature - Adding checksum to NMEA sentences

[Serge Robitaille]

Newly released OpenCPN 5.12 systematically rejects NMEA 0183 sentences without checksum. It looks like a retired feature at the moment ?

SeaTalk interface, originally developed by Autohelm in the early 1990’s, was included on  Autohelm and Raymarine (and some Raytheon) products up until about 2012. As a result, there are thousands of boats around the world that have a SeaTalk 1 network. Many of these owners need to convert from SeaTalk to NMEA 0183 to share navigation. OCPN is one example... the Radar Plug-in needs magnetic heading for the overlay to work as well as other plug-ins like Tactic Dashboard to display depth, wind speed & direction, wind angle and other navigation data present on the Seatalk Network.

The Raymarine’s SeaTalk to NMEA converter does not add a checksum to NMEA 0183 sentences... the newer converters do, but they are expensive and often come with  NMEA multiplexer built-in function.

Adding a checksum to checksumless NMEA 0183 sentences would probably help a few of us out there with legacy navigation systems.

Thank you for your time and for your consideration

 

[Keith Young]

Good news!  This is already done!

Bad News: For several years the "develop" branch has contained a number of new feature and fixes.  I've just been waiting to get round to remembering how to build a deb package.  So currently you need to either git clone the develop branch https://github.com/stripydog/kplex/tree/develop

There's 2 new arguments to the checksum option.  From the README:

        "checksum": Overrides the global checksum option for an interface. If

            set to "no", no checksum checks are performed on incoming sentences.

            If set to "yes" or "strict", incoming sentences without correct

            checksums are discarded.  If set to "loose", sentences with

            incorrect checksums are discarded but those without any checksum

            are permitted. If set to "add", sentences with incorrect checksums

            are discarded but where no checksum is present, one will be added.

            If set to "addonly", a checksum will be added if absent but

            sentences with incorrect checksums are accepted.  With "add" and

            "addonly", sentences without checksums are discarded if the addition

            of a checksum would exceed the maximum permitted sentence length.

Yes yes I need to build a new deb....