Connection between only 2 NMEA2000 devices
Is it possible to connect only 2 NMEA2000 devices with a single cable without passing through a N2K bus with backbone, T’s and terminal resistors (taking into account that the +V and ground wires must also be coonected to the 12V supply)?
5 Replies
No. You need terminators.
It depends on the devices. Some devices have a built in terminating resistor that you just need to enable. If you have two devices with this then you can connect them directly.
I found that people in labs, for the ease, simply use 2 wires (usually a twisted pair), shorted with a single 60 Ohm resistor, to connect 2 (or sometimes more) CANbus modules. This works as long as the length of the connection(s) is very short. I shall test it when I go to the boat in the spring.
Yes, this works fine. And the cables don't have to be that short, either. The maximum drop cable length (the cable from the backbone to a device) is 6m. Also, a minimal backbone is a 5-way T-connector with two terminators. With such a backbone, it doesn't really matter whether you have two separate terminators or one with both terminated resistances clumped together in parallel. Hence, you can "legally" have a star topology network with clumped terminators at the hub as long as the drop length is less than 6m (and the total drop cable length is less than 78 m). A bus topology with short drop cables is still preferable, but N2K isn't that fussy. 🙂
@Matti. Thank you for the confirmation. A N2K network starter kit (cables, one T and two terminal resistors) cost more than the module I want to connect to my plotter.