I recently worked on fixing a PLC system in a boat that used the NMEA2000 standard which basically is a CAN standard build on J1939 and uses a M12-5 identical to the one I used earlier on a waterproof CAN box. NMEA2000 define format for a range of sensors so that sensor and receiver actually is plug & play. You find a lot of NMEA2000 equipment in boat gadget shops and it has a well defined CAN cabling standard making it very attractive for Electric Vehichles in general (not just boats). Existing sensors and equipment is mostly boats, but that should not stop us. The bitrate is defined to 250Kbps and the actual standard documents is one of those that cost money, but information is available in the community.
My new CAN box uses DB9 rather than M12-5A which is not waterproof, but cheaper and more standard for CAN in general + a bit better for a desctop or plain PLC box. The 88mm x 38mm boxes I use is however waterproof IP67, so if I change back to using M12’s on the front I only need a few modifications on the USB, Ethernet, SD-Card and Power on the back panel to be completely waterproof. This will add a bit to the cost, but it is a big win to get back on a IP67 standard.
The 3D image above is from my 12 x Analogue board that uses M12 connectors – I only need to modify the other side of the board for this to be waterproof and fully boxed as a module. I can support 4 x M12 on each side in a modified design.
Power can be a M12-2 supporting 12-24V In.
Ethernet can be converted to M12-4 or M12-8 waterproof with ca the same space usage.
USB can be removed or hidden behind a waterproof lid.
SD-Card can be removed or hidden further in on the PCB.
The J1939 part of the standard is dead easy since I also worked a lot with building Electrical Vechicles lately.
NMEA2000 makes it attractive to move back from DB9 (D SUB 9) to M12-5 even is M12-5A cost a bit more on the connector side. It uses less space and the waterproof side makes it worth it IMO. Adding NMEA2000 options in SW means equipment goes plug & play on an attractive boat maritime marked as well.
My first and most obvious move would be to make a 3 x NMEA2000 adapter – converter from CAN to Ethernet – and then connect Ethernet to Raspberry PI for HMI.
NMEA2000 also have an Ethernet sibling we can explore.
The 250Kbps on NMEA2000 is not a good match for 12Mbps CAN-FD ports, but the lower 250Kbps is probably much better for CAN networks with multiple sensors on.