Problematic. Even if N2K had been completely reverse engineered, there would still be a bandwidth problem. NEMA-0183 has barely enough bandwidth for GPS; Garmin fast GPSes require cranking NMEA-0183 up to 9.6K baud, which is both non-standard and not supported by more peripherals. AIS sentences, sent at 38.4K baud, would be a disaster. And even if you cranked NMEA-083 up to 38.4K baud across the board, I doubt that many devices would accept it.
NMEA-0183 sentences over UDP is a de facto standard. OneNet (NMEA over IP) is N2K sentences over UDP but almost certainly with a crypto handshake to keep non-NMEA licensees from tapping in.
Has anyone looked at taking N2K sentences as input and output them as NEMA-0183.
Steve
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Has anyone looked at taking N2K sentences as input and output them as NEMA-0183.Steve
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And it only costs $300!
A $10 GPS dongle, a $10 USB to RS-232 dongle, a $35 Raspberry Pi, and a tiny bit of programming and you're done. Find a dozen other useful things to keep the Pi amused shouldn't be hard.
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-- Jim Starkey
https://digitalyachtamerica.com/product/ikommunicate-nmea-signal-k-gateway/
Perhaps I've missed something. Last I heard, the agreement between Signal K and NMEA was that NMEA would bless Signal K as long as a NMEA licensee produced the box.
There are two sticking points. One is a CANbus (N2K) / USB gateway. These are in the range of $200. And that's for the hardware, so you're not out of the woods yet.
But then, again, I may have missed something. But intellectual property issues aside, CANbus is extremely computer unfriendly and doesn't have the bandwidth to transmit a radar image, chart, sonar image, or any form of video, so I very little interest in it. My boat has Seatalk instruments, 183 links between autopilot and chart plotter, wired Ethernet between chart plotters and radar, Ethernet between masthead WiFi router and an RPi functioning as a wireless router, WiFi from a Raymarine E7 to iOS devices, two Seatalk / 183 / rs-232, etc. In short, a mess. I want a single Ethernet/WiFi network with enough bandwidth to keep everyone happy. N2K will never be in the picture.
If you want a cheap GPS data source, a couple of dongles and an
RPi is by far the way to go. And it it has Ethernet.
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-- Jim Starkey
That's fine as long as you keep the AIS gook off the 4kb links.
But the original question was about N2K.
Jim, I accept 38.4K baud NMEA 0183 sentences for AIS plus GPS from my Standard Horizon DSC VHF radio into my boat's Beaglebone Black running OpenCPN via a serial-to-USB 2.0 4-port hub. I'm able to use that to navigate plus display and target query AIS contacts, plus output that data to my B&G Network instrument system on a 2-way 0183connection at 4800 baud, no problems. That also makes the AIS, GPS, and wind, depth heading, speed, water temp., etc. data available to KPLEX where I broadcast it over 802.11N wi-fi to my home network where NavMonPC running on a Windows 8.1 PC accesses it for remote display and logging.
Alan Hails
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-- Jim Starkey
What I said is that many devices, chart plotter for example,
won't take regular 183 data off a 38.4 kb connection. I haven't
tried it, but Raymarine says it doesn't work, at least on the E
wide series; the "high speed" serial port can be either general
183 at 4kb or dedicated AIS at 38.4 kb. And I said that AIS
sentences on 4kb links would be a disaster, which if you look at
the sentence length for AIS messages and the total lack of flow
control on 183, should be obvious. AIS is intended to work at
38.4kb.
Yes, Jim, and one of your incorrect statements is that 38.4K Baud NMEA 0183 data is useless, cannot be accepted by other devices, and AIS at that rate would be a disaster...
Alan Hails
-- Jim Starkey
I've checked the Raymarine documentation and it appears that most of their chart plotters will accept general NMEA 0183 data on a port set to 38400 baud, though historically only support one port for that baud rate.
The reason that a device might not support general NMEA 0183 as processing AIS data is radically different from other sentences in that AIS messages are broken into multiple sentences, are ASCII encoded compressed binary. And since the first character gives it away, there is no logical reason that any NMEA 0183 parser can't handle both, but remember we are dealing with software engineers that preferred to use speed through the water rather than speed over the ground for computing true wind direction. But we can hope they have since gotten smarter.
The getting back to the original point, I submit that a dedicated GPS is a hell of lot cheaper than trying to tap GPS data from N2K.
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but remember we are dealing with software engineers that preferred to use speed through the water rather than speed over the ground for computing true wind direction.
The getting back to the original point, I submit that a dedicated GPS is a hell of lot cheaper than trying to tap GPS data from N2K.
Looks perfect. What do you run it on.