Trying to understand how I can interface with NMEA 0183 and/or SeaTalk to read instrument data from a sailing boat.
Course Computer is Raymarine Autohelm 100/300
From what I can see it looks like there are 2 options:
NMEA output from the Course Computer: Would require an RS-422/485 Hat to sit ontop of the RPi4
SeaTalk cable that I can use an Optocoupler to transform the 12v down to 5v then connect that directly to the GPIO pins on the RPi4 e.g. here:
Connect Seatalk-1 devices to Openplotter using GPIO - YouTube.
Am I correct in my understanding or is there a cheaper/easier route?
Thanks in advance!
From the looks of things, Seatalk is going to be cheaper and easier to get working. Looks to be a 1-wire communication bus. An optocoupler is a great idea in either case, an RS485 HAT will likely use one anyway.
Are there any trade-offs data-wise for choosing one or the other?
Here are two options from our store to give you an idea on price:
This is a 2-channel isolated RS485 expansion HAT designed for Raspberry Pi, adopts the SC16IS752+SP3485 solution, with embedded protection circuits such as power supply isolation, ADI magnetical isolation, and TVS diode, etc.
Price: AUD 34.95
Keen to hear your thoughts!
Hi Kevin (and James)
I would go with the NMEA model as that is a very well defined protocol and quite straight forward to disassemble for display.
FYI I am considering using it ( or a reasonable subset ) between a remote weather station head and the display system.
Also this module is available
Thanks very much for your input, guys!
Looking at the manual it seems that the SeaTalk network exposes additional data that isn’t available on the NMEA outputs.
If I went down the Optoisolator route I would still need the resistor from the 12v wire before connecting to the optoisolator right?
Sorry for my newbie-ness as I’m just learning electronics, but I have been developing web-based software for decades so once I can read the data then the rest will be easy.