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Alternative SeaTalk wiring
#11
Thanks for reporting Duncan.

Please try the new wiring.

You can also try the old wiring but adding a 4.7K or 5K resistor in serial with the MacArthur Seatalk1 DATA connector. That will give us more clues.
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#12
Ok, I’m back at the boat and with the new wiring, inverted, and jumper set to ST and/or removed I only see navigation.log and navigation.trip. I then waited about two mins and headingMagnetic and rudder.angle appeared. After some more time gnss appeared with a null value. I’ll wait a little longer to see if I get more fields but it seems very slow and is if there is too much resistance/low signal strength.

Anything else I can do to test this for you?
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#13
Can you remind me whether the original Seatalk wiring worked with your setup or not?

If you have a volt meter, can you check whether the ST Data line idles at 12V?
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#14
(2023-05-26, 11:29 PM)Adrian Wrote: Can you remind me whether the original Seatalk wiring worked with your setup or not?

If you have a volt meter, can you check whether the ST Data line idles at 12V?

Mine works correctly with the old wiring and has done with the HAT and the Octo I used before. It does not idle at 12v. The highest I’ve seen on the multimeter is 6v but it’s bouncing from 0 to about 5.
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#15
So much for my theory. If Seatalk data idles at less than 12V its surprising that you get any data at all with the alternative wiring.

Caveat, measuring with a multimeter is problematic as it will average voltage levels if there's active traffic. I recently came across this site, which also says that data idles at 12V: http://www.thomasknauf.de/seatalk.htm

Two alternative explanations:
  1. The signal on the Raspberry Pi side of the optocoupler isn't "digital" enough to be properly decoded
  2. The Pi drops bits as it can't read the GPIO consistently enough to decode at 4800 baud - though not clear why that wouldn't be an issue with the original wiring

I think I will have to get my hands on a Seatalk1 system to debug this issue.
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#16
Hi

I'm back on board testing the seatalk connection on the HAT this afternoon.  With the new wiring, inverted and ST jumper set, the STLINK FAIL error doesn't occur (postive). However, although I get several variables coming through in Signal K, all of them are null values. I sat here for about 1/2 an hour and nothing.

I then put the wiring back and removed the invert signal, the STLINK FAIL error came back on the autohelm but all the data for the wind and tridata instruments started to appear...

I forgot to bring down my resistor pack so I can't test the resistor and the old wiring at the moment.

Hope that helps
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#17
Thanks a lot Duncan. I think that is very helpful. Some questions:

- was the ST jumper in the open position or removed with the new wiring?
- does "several variables" mean data that should come from the wind and tridata seatalk instruments?

Adrian will correct me if I am wrong but I think your result confirms our latest conclusions. The important thing of your test is that using the new wiring your seatalk bus and devices keep talking and the STLINK FAIL error is gone.

Null values could also confirm some issues observed by Adrian. In the other part of the circuit (after the opto) we do not have a clean and square digital signal but a rounded one with some soft valleys making it difficult for the Raspberry to interpret what is 0 and 1. That could explain why you can see signal k keys translated from the seatalk data but erratic values and Boatingbaileys's results. This effect is less visible using the old wiring but is still present.

We have some new prototypes on its way using the new wiring and replacing the opto by regular transistors which have faster switching times. Elements to protect the Raspberry has been added as well.

I am still interested on your test with the old wiring adding a 4.7K or 5K resistor to the seatalk1 DATA connector. That could give us more info about the seatalk1 bus behavior.

Thanks again.
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#18
To add to what Sailoog wrote:

With the new Seatalk wiring, the signal that the Raspberry Pi sees can be squared up by adding a resistor between pin 38 (GPIO 20) and pin 39 (GND) of the 40-pin header*. Any resistor value between 1K and 10K should work, with lower values making for a sharper transition between 1's and 0's. See https://pinout.xyz/# for a reference of the pin numbering.

This patch adds a resistor in parallel to resistor R21 (R2 in the schematic at the start of this thread), reducing the total value of the pull-down resistor. For a tidier fix, those experienced with SMD soldering can piggy-back a 0603 sized resistor on top of R21.
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#19
Hi Sailoog

Just to answer your questions;

- The ST jumper is in the position depicted in your drawings at the start of this thread 
- The variable -as I described them are- is the data that is coming from the wind and tridata instruments.

Just to add, with the new wiring, I'm seeing the seatalk LED flash (as you described). When I switch back to the original wiring then the LED is more solid.

I've tried re-cabling the seatalk network so that my tridata instrument is the first device on the seatalk bus but if I use the original wiring the Authohelm still comes back with STLINK FAIL error and I can't use it. If I switch it to the new wiring, the and it doesn't get the error but all the data is null. Really frustrating cause I can't effectively use the seatalk bus becuase it knocks out my autohelm.

I'm not sure it's relevant but the autohelm is the only device that has it's own dedicated power. The tridata and the wind instruments are getting there power from the autohelm via the seatalk one network.

I will come back next week and try the resistor.
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#20
(2023-06-02, 01:36 PM)Duncan Wrote: Hi Sailoog

Just to answer your questions;

- The ST jumper is in the position depicted in your drawings at the start of this thread 
- The variable -as I described them are- is the data that is coming from the wind and tridata instruments.

Just to add, with the new wiring, I'm seeing the seatalk LED flash (as you described). When I switch back to the original wiring then the LED is more solid.

I've tried re-cabling the seatalk network so that my tridata instrument is the first device on the seatalk bus but if I use the original wiring the Authohelm still comes back with STLINK FAIL error and I can't use it. If I switch it to the new wiring, the and it doesn't get the error but all the data is null. Really frustrating cause I can't effectively use the seatalk bus becuase it knocks out my autohelm.

I'm not sure it's relevant but the autohelm is the only device that has it's own dedicated power. The tridata and the wind instruments are getting there power from the autohelm via the seatalk one network.

I will come back next week and try the resistor.

Ok thanks for answering. That was just to be sure before moving forward.

The flashing LED is a good thing. It means that your seatalk1 bus is talking including the autohelm. The problem now is that the Raspberry can not understand because there are still electrical issues after the opto.

Do not get frustrated, your test has been most useful, we will make it work for sure. Actually, I think the external resistor and the old wiring will work, but when we get the new wiring to work, it will work better.

I do not think the power is the problem unless you are also powering the raspberry from the seatalk network and the autohelm is not getting enough juice.
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