Watcheye/OceanSat Class B transponder isn't recognized by kplex on Raspi 3B

[Helmut Fischer]

Hello,

this is my first posting here, I discovered the group only yesterday.

For about a week I am trying to setup a Raspberry PI 3B system with kplex for transmitting AIS data from my home to Marine Traffic. AIS and MT work nicely with OpenCPN on a Mac Mini. With a masttop rod antenna under the roof of my home I get about 100 AIS messages per minute at average, and I sometimes (but rarely) have reception ranges up to 50 nm. My AIS is a second-hand OcenSat Class B Transponder (not produced anymore), physically identical to this device:

<https://watcheye.nl/en/products/watcheye-b-class-ais-transponder>

Sendig AIS messages is disabled by a hard-wired bridge.

Whatever I tried, I can't get it to work with kplex. I then tried another old second-hand AIS (easy-AIS IS by WeatherDock), and that one works with kplex! But it is less sensitive (about half the number of messages with the same antenna), and therefore I would like to get the OceanSat to work. Both AIS devices have USB ports, which I use for connecting to Mac and Raspi. The OceanSat can be powered via USB (but I also tried it with external power, applied before booting up the Raspi), the easyAIS needs external power.

I know some electronics, I know how to enter terminal commands, but I am not a Raspberry or programming expert. Any idea how I could try to find the bug?

Many thanks in advance,

Helmut, Bremen, Germany

[Helmut Fischer]

in response to my own question:

I found a workaround: I installed openCPN on the Raspberry, connected the OceanSat AIS, set up the trandfer to MT, and it works. However, I still would be interested in a solution of my original problem, as a kplex system would be much simpler than an openCPN system.

Regards, Helmut

[Keith Young]

Apologies for the double post if I accidentally hit "reply to author" on my previous response...

If:

* one AIS unit works but the other doesn't with the same kplex config

* opencpn works with both

...my best guess is that the non-working AIS unit is not terminating sentences sent over USB according to the NMEA-0183 standard.  OpenCPN is not particularly strict about line termination.  kplex adheres to the standard unless you tell it not to.

Try adding:

strict=no

to the section of your kplex config which defines the AIS usb interface.  This tells kplex not to be too fussy about sentence termination

[Helmut Fischer]

Hello Keith,

thank you for the prompt reply.

Unfortunately, adding "strict=no" to the config file didn't help. But I remember having seen all kind of strange "garbage" in the NMEA debug window of openCPN. Maybe the AIS allows for filtering the output, I will try and report.

Yours, Helmut

[Keith Young]

Can you try capturing a couple of lines wfrom the device with "od -c", e.g.:

stop kplex/openscpn

od -c < /dev/ttyUSB0 (or whatever your AIS device is)
ctrl-C when you've got a couple of lines