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Seatalk
#1
I am attempting to get my Seatalk instruments to connect to OpenPlotter (particularly depth) but so far no luck.

I have the opto-coupler with 4.7k ohm resistor.  My version of Signal K is 1.46.3 which I understand should be able to read the Seatalk data.
The hardware is a RaspberryPi 4-B with 8gig memory.  Because I have pypilot, I'm using GPIO 6 and 13 for Seatalk (2 opto-couplers).

If I run sudo python STALK_read.py, I get data but it seems to drop characters and then out of the blue it displays a dozen lines of what looks like complete data.  So some data is coming through and maybe the test program isn't presenting it correctly.  I'm testing using my Seatalk Wired AutoHelm Remote Control which means I can push the button and then see what is presented on the screen.  I doubt SignalK would understand the message but I would think it should register something.  Additionally I would think that SignalK would understand depth out of the box and it is not.  SignalK shows a green started connection but never shows any data (no yellow line).

If I ever get it working, is there anyway in SignalK to map in the Seatalk autohelm sentences?

I'm wondering if the 4.7k resistor is too much or too little.  I can see the LED flashing on the opto-coupler but it's a very subdued flicker.

Any suggestions on what rock I can look under to get SeaTalk and SignalK working would be appreciated.
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#2
Make sure you have pigpio installed and running.

You might find some inspiration here https://github.com/marcobergman/seatalk_convert, if only for the electrical hints, as I am a bit weary of many of the interfaces I see recommended. Don't understand why you have 2 opto-couplers, as you can tie seatalk-1 lines together?

On one hand, this python script can read seatalk from any GPIO and makes NMEA sentences from it. I built this because I have no signalk on the raspberry that my seatalk instruments are connected to. It does not do depths (I have depth from a nmea0183 source) but if you send me your example seatalk datagrams I'll see what I can do.

On the other hand, the SignalK interface does indeed seem to have the depth datagram (00) already implemented. As for the autohelm datagrams, you have to be more specific.

Cheers, -
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#3
I replaced the 4.7K with a 10K and it worked fine. My setup is shown in this video with the ST1 stuff at 7min30:

https://youtu.be/enPFlHpmJVA
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#4
Anyone tried using an op amp before the opto coupler?
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