I created this document to aid in CAN bus debugging for the bus wiring, connections, and terminations.
If the bus wiring is incorrect:
There is a web link in this document that has good technical information on the physical layer (wiring, connections, termination, etc)
It looks really good - the only comment I would make is on what wires users should use for the CAN bus.
Users should use 28 AWG stranded twisted pair wires with an approximately 120 Ohm characteristic impedance like:
For wires that’s all in one (ie single 28 AWG twisted pair for the CAN bus and 2x 22 AWG wires for 24V power) for tool head PCBs, like the BTT EBB36/42 or Mellow FLY SHT36/42 I use the Tensility cable:
As a final note, twisted pair cables should be purchased by the foot (or cm) - 100’ (30m) spools of these cables can cost $500 or more.
The Texas Instruments doc link in my guide states 24 gauge wire for the bus.
It shows the signals on un-terminated as well as properly terminated.
It also shows noise introduced by fluorescent lights on unshielded twisted pair and shielded.
If fluorescent lights can introduce noise, then stepper motor wires can also do the same.
Most I have communicated with that don’t have issues with their CAN bus setup use shielded twisted pair.
The TI document only references 24 AWG twisted pair. It does not “state” or specify using that gauge of wire. I shouldn’t have been so definite in saying users should use 28 AWG, apologies for that. Twisted wire gauge should not matter as the point I was trying to make was that users should only purchase twisted wire cables that have 120 Ohm characteristic impedance (and not try to twist it themselves).
I agree that the optimal situation has shielded twisted pair cables with a shield and one of the shield tied to ground (to avoid making a ground loop). It’s actually hard to find twisted pair cables without a shield of some kind.
The cables that were suggested are ones that I have used in my own printers with the Tensility being simple to use, quite flexible fairly low cost and combines the CAN bus twisted pair with power wires heavy enough to provide sufficient current to the toolhead controller which makes for a nice, neat package.
My attempt is a first draft, and the information provided is the basic debugging I find when helping a user typically fails.
Some think you connect CAN-L to CAN-H since they only have experience with UART connections.
Some don’t provide termination or are inexperienced with crimping the pins for the connectors, and they fall out of the connector.
Some try to use CAT5 solid wire for tool head wiring.
