Seatalk input, MacArthur HAT and rpi5. Options?

[gpatsiaouras]

Hello everyone,

In my boat I have the ST60+ wind instruments that have a seatalk1 output that I would like to read it using the MacArthur HAT. The official announcement is that Seatalk input does not work with the Raspberry pi 5 because of some gpio change. My questions are:

1. Is the seatalk input something that will never work with the RPI5 due to hardware limitations, or it's something that is just not implemented yet?
2. If it's never going to be fixed, do you have any suggestions on how to read the seatalk input? I see two options, using a raspberry pi 4 instead, or using some external seatalk -> NMEA0183 or usb. Though the latter one is very expensive and I would try to avoid.
3. Other options?

Thanks in advance,
George

[abarrow]

I'm pretty happy with my SeaTalk->NMEA converter.from YakBitz. They have a wired and a USB version. Both are $69(aus) delivered. https://www.yakbitz.com/Default.aspx

[Sailoog]

There are no hardware limitations on Raspberry 5, even Raspberry 3 can bit banging any GPIO at 4800 baud. The current limitation of the Raspberry 5 is the software. The hardware architecture changed a lot on Raspberry 5 and the pigpio library no longer works on it. This library was the only one capable of bit banging 4800 baud 9bit and there are no plans to update it.

I have been doing some testing with current and active libraries, but none are ready for this. I want to do one last test before throwing in the towel.  I am pretty sure this will work, but we may need help here.

I want to try libgpiod - gpiomon. It has nanosecond granularity and allows for biases, edges, and even buffering, so I think it can work. Any help is welcome.

[TVR]

There are a few options discussed in this thread.

Seems like gpiozero is the "recommended" way forward, and the documentation seems to imply it can do bit banging.
https://gpiozero.readthedocs.io/en/stable/api_pins.html

I'm not an expert, but hopefully this helps?

[gpatsiaouras]

There are no hardware limitations on Raspberry 5, even Raspberry 3 can bit banging any GPIO at 4800 baud. The current limitation of the Raspberry 5 is the software. The hardware architecture changed a lot on Raspberry 5 and the pigpio library no longer works on it. This library was the only one capable of bit banging 4800 baud 9bit and there are no plans to update it.

I have been doing some testing with current and active libraries, but none are ready for this. I want to do one last test before throwing in the towel.  I am pretty sure this will work, but we may need help here.

I want to try libgpiod - gpiomon. It has nanosecond granularity and allows for biases, edges, and even buffering, so I think it can work. Any help is welcome.

Hi Sailloog,

That's good to hear (that it's not a hardware issue) because I'd really like to use the HAT instead of an external solution.
I can definitely offer help, I am a software engineer myself as my day job, eEspecially if it's python/javascript. Hardware I do as a hobby. If you can give me some pointers or specific things I can do to help you, maybe some links to docs/github repo, I can get to it.

Thanks!

---

I'm pretty happy with my SeaTalk->NMEA converter.from YakBitz.  They have a wired and a USB version. Both are $69(aus) delivered. https://www.yakbitz.com/Default.aspx

That is a good alternative yeah, if all shit hits the fan with the rpi5 and gpios. 69$ for shipping to europe is quite good. Thanks I'll keep it in mind

There are a few options discussed in this thread.

Seems like gpiozero is the "recommended" way forward, and the documentation seems to imply it can do bit banging.
https://gpiozero.readthedocs.io/en/stable/api_pins.html

I'm not an expert, but hopefully this helps?

Yes appending to what sailoog mentioned since the GPIOs software is the culprit it makes a lot of sense to work towards a rpi5 specific solution. That's a good starting point thanks.

[Sailoog]

OK, thanks. This is the background of the problem in case someone can help:

The most important reference is this one where seatalk1 is explained: http://www.thomasknauf.de/seatalk.htm

In part 1 is the explanation of the serial protocol and it is the important one. In part 2 are the datagrams but that is already read by the Signal K server. In part 3 is the electrical part that is already solved by the MacArthur HAT.

Currently we are using pigpio to read serial data at 4800 bauds and 9bit. This is the python script embedded into Signak k: https://github.com/SignalK/signalk-serve...seatalk.js

Basically what we need is to replicate what pigpio does: https://github.com/joan2937/pigpio

[gpatsiaouras]

OK, thanks. This is the background of the problem in case someone can help:

The most important reference is this one where seatalk1 is explained: http://www.thomasknauf.de/seatalk.htm

In part 1 is the explanation of the serial protocol and it is the important one. In part 2 are the datagrams but that is already read by the Signal K server. In part 3 is the electrical part that is already solved by the MacArthur HAT.

Currently we are using pigpio to read serial data at 4800 bauds and 9bit. This is the python script embedded into Signak k: https://github.com/SignalK/signalk-serve...seatalk.js

Basically what we need is to replicate what pigpio does: https://github.com/joan2937/pigpio

Alright I think I have enough info. I will check what I can do.