Discussion and questions related to the course EFI Wiring Fundamentals
Been reading up on Canbus the last few days and getting further and further into the possibilities of it all.
We have all seen the generic wiring diagram of a Canbus system with the twisted pair running across the page and all the devices above or below it tapped off this pair.
Real world, is this strictly necessary? say a system with 10 different devices spread across the vehicle, it may be neater and easier to run a twisted pair to each device and then splice them together at a central point, similar to how say power to a set of coils power may be wired? Then wire your terminating resistors at the ends of the longest splices?
I realise this is an unlikely scenario, but it came to me while daydreaming about a universal power system that used Can to talk to all the bits.
You will have problems if you attempt a "star configuration". Yes, we really do run a wire from the front to the back, and across as necessary. Terminate at each end, and keep the twists tight and you will have reliable CAN communications at the highest baud rate.
I've wired devices in a star configuration and haven't struck any problems, but there were only four devices, two of them had built in termination resistors and the harness length was pretty short.
I couldn't recommend doing it with a longer harness length (getting up toward 2m or longer) or more devices. Is it going to be tricky to run a main bus line through the vehicle that can be tapped for the rest of the devices?
As stated before, CAN doesn't work well with a star topology. You could run a daisy chain from device to device but you need to have one main bus run. Stubs can be used but should be kept short. Preferably under 1m.
Thanks everyone, purely curiosity here with no actual real harness, better to know than assume.