How hard is setting up CAN connected boards?

gloomyandy

@droftarts I'd agree with Jay that the increased use of stubs to connect to boards and a lack of documentation on this (and especially with the tdb) makes things more complex. I also think that the rather confusing set of different connectors used on the different boards does not help. In general CAN-FD is very tolerant of wiring problems (I have a very dodgy bench setup that I use for testing), but when things go wrong it can be hard to work out what the cause is.

I suspect that more work is needed on the initial setup conditions in particular when using more than one mainboard configured as a can expansion board as they will initially startup as a "bus master" which an cause problems with other boards thinking they have found the "actual mainboard".

droftarts

@gloomyandy @jay_s_uk I'm currently adding more documentation for the TDB (see https://forum.duet3d.com/post/341018 as a start). I've added a section on stubs, see https://docs.duet3d.com/en/User_manual/Machine_configuration/CAN_connection#wiring-scheme, but perhaps more examples with real boards are needed. People seem to like diagrams, but they do take a long time to produce.

Ian

deckingman

@droftarts My only bad experience was intermittent loss of CAN connectivity with a 1LC toolboard. It turned out that the issue was with the supplied, pre- wired JST ZH connector (bad crimp most likely). Not sure what Duet could do about that short of making a test rig and "wiggling" the wires around.

engikeneer

@droftarts I'd say the general idea of CAN is brilliant and massively simplifies the setup over older non-CAN printers.

However the mix of different connector types used and mix of 2-wire and 4-wire adds some confusion and complexity. The simplicity of the RJ connectors on the 6XD and 3HC is brilliant, but try adding a Mini5+ or toolboards in there and you're back to fiddly crimps or burning yourself with solder sleeves. I basically had to wire up my toolchanger twice because of hard to trace issues and intermittent connection problems when I made up my first set of cables.

My preference would have been for Duet to supply a set of standard length cable options. Even if they were excessively long for my build, I think a few coils of properly made cables would be preferable to the bundle of home-made mess on either end I have on my toolboard connectors.

droftarts

@engikeneer I tend to agree. The simplicity of CAN using RJ11 connectors is great. Perhaps a useful addition to the documentation would be to list what the connectors are, something like this?

Board	CAN OUT	CAN IN	Extra outputs	Termination
Duet 3 Mainboard 6HC	RJ11	-	-	On by default, drillable via to remove (v1.02 and later)
Duet 3 Mainboard 6XD	RJ11	-	-	On by default, drillable via to remove
Duet 3 Mini 5+	2-pin KK	-	-	On
Duet 3 Expansion 1XD	RJ11	RJ11	-	Off by default, jumper to enable
Duet 3 Expansion 1HCL	RJ11	RJ11	-	Off by default, jumper to enable
Duet 3 Expansion 3HC	RJ11	RJ11	-	Off by default, jumper to enable
Duet 3 Tool Distribution Board	RJ11	RJ11	4x 4-pin JST ZH to toolboards	Off by default, jumper to enable
Duet 3 Toolboard 1LC	4-pin JST ZH		-	Off by default, jumper to enable (v1.1 and later)
Duet 3 Roto Toolboard	-	XT30 2+2	-	Off by default, jumper to enable
Duet 3 Scanning Z probe	-	4-pin JST PA (2 pins of)	-	Off by default, solder jumper to enable
Duet 3 Motor 23CL	M8 4-way connector		-	Off by default, solder jumper to enable

The problem I have for documentation is that there is hundreds of variations of ways to connect multiple boards together. Unfortunately, I'm not clever enough to develop a web tool to create a personalised wiring diagram for each variation!

Ian

DIY-O-Sphere

@droftarts said in How hard is setting up CAN connected boards?:

The problem I have for documentation is that there is hundreds of variations of ways to connect multiple boards together

In my opinion, no diagram is needed for such complex wiring. Such machines are only built by experts.
The documentation with the new diagrams is the right way to go.
The section "Expansion board connections" definitely needs illustrations / images.
It's a pity that the illustrations of wiring the 1LC are no longer available. Dozuki
Among those who voted with easy are some who started with the old documentation .....;-)

droftarts

@DIY-O-Sphere Thanks for the suggestions, that's what I'm planning on.

The 1LC wiring diagrams are still in the current documentation though! See https://docs.duet3d.com/Duet3D_hardware/Duet_3_family/Duet_3_Toolboard_1LC#can
Click on the "Connecting WITHOUT Duet 3 Tool Distribution Board" tab.

Ian

DIY-O-Sphere

@droftarts said in How hard is setting up CAN connected boards?:

Click on the "Connecting WITHOUT Duet 3 Tool Distribution Board" tab.

Oh yes, the tabs....I sometimes overlook them. I'm probably not the only one....

o_lampe

@droftarts I don't have any boards with CAN, so I didn't vote and can only add my general experience:
By using shielded twisted pair, the user needs to know how to wire the shield. AFAIK, it is connected only on one side?
But what about daisy chaining CAN boards? Where would one connect the shield? Is it possible to accidently connect them wrong?

Same thing with termination. There are 1001 variants to connect the various boards. How clear is it for the user to terminate them correctly?

jay_s_uk

@o_lampe there's no need to shield the CAN wires

oliof

@droftarts I think it would be sufficient to provide some example diagrams:

single toolboard to the print head
using a duet3d board as expansion board
tool changer with TDB and multiple tool boards

Anything else likely will need extra explanation and/or expert input anyways.