Attitude data expressed as frequencies/amplitudes

[jkross]

I know about the PGNs for heave (1217252) and attitude (127257), which report instantaneous values.

I am interested in displaying frequency/amplitude for heave, pitch, roll and yaw. I can compute these values using FFTs, but can't find a standard way to report them on the NMEA2000 bus.

What's the proper way to do this? Did I just miss the official PGNs? Should I use a vendor-specific set of PGNs and then write parse/set functions on the signal-k server that will add this information to the signal-k stream?

I think I want to report the top two frequency/amplitude pairs for each measurement.

BTW - this is being processed on a

• Adafruit Feather M4 CAN
• BNO055 9DOF absolute orientation IMU

[mairas]

Neat idea. I don't think there are any standard PGNs for such frequency information, so you'd indeed need to roll your own if you want to use N2K. One slightly more esoteric but potentially applicable solution would be that Scott Bender implemented an experimental PGN that would transmit SK deltas encapsulated in an N2K fast packet. I'm ashamed to admit I still have never tested it, though.

[jkross]

Neat idea. I don't think there are any standard PGNs for such frequency information, so you'd indeed need to roll your own if you want to use N2K. One slightly more esoteric but potentially applicable solution would be that Scott Bender implemented an experimental PGN that would transmit SK deltas encapsulated in an N2K fast packet. I'm ashamed to admit I still have never tested it, though.

Can you point me to this experimental PGN? Is it in the production server?

[mairas]

It seems like I remembered wrong. It's a separate plugin: https://github.com/SignalK/signalk-over-n2k. I guess that's a good thing in this case - easier to test and debug if/when needed!

[jkross]

Thank you!

[tkurki]

Just pointing out the obvious: nothing else will understand a custom PGN, so apart from a wired connection there is no particular value on having it in N2K I can think of. You could skip N2K and push the data directly to SK over TCP/IP.

[jkross]

Just pointing out the obvious: nothing else will understand a custom PGN, so apart from a wired connection there is no particular value on having it in N2K I can think of. You could skip N2K and push the data directly to SK over TCP/IP.

I agree. I don't have TCP/IP on the Feather.