T2260 BOB Wiring & Config on Stepper Channel 10

Danger

I'm' working on my third and most advanced conversion to Duet WiFi and I've hit a snag. In order to put both my Z-axis steppers on internal drivers for bed compensation, I've been trying to repurpose the onboard E1 driver, and then put that extruder (for a dual extruder system) back into the configuration using a TMC2260 BOB. I originally thought it would work like a Polulu-style board as described in Using External Stepper Motor Drivers, but that didn't pan out. After multiple searches, I found this post TMC2260 on Stepper Channels 10 and 11(asking related questions, but not exactly the same situation). I'm not interested in building my own board from a bare chip -- I was under the impression this BOB would make it possible without that kind of scratch build.

Before I spend time and take any risks, I want to get some guidance on my proposed approach. This diagram is my interpretation of the tips listed in the discussion referenced above. The two questions I have boil down to:

Is the diagram below correct?
Per the comments in the TMC2260 on channels 10/11 thread -- this will require customizing my own firmware?

If the firmware mods are required, that will be a new field of study for me, and not really excited about deviation from the released code.

Any guidance appreciated.
0_1557611657754_T2260BOB Wiring-v2.jpg! 0_1557611811763_T2260BOB Wiring-v2.jpg

dc42

Your connections look OK to me, but check whether you need to connect CLK16 to ground. The TMC2660 can use an internal or external clock, and to use the internal clock its CLK pin must be grounded. I don't know the TMC2660_BOB so I don't know whether CLK16 is connected to the TMC2660 CLK pin or not.

You will need to modify the firmware. If you also have a DueX5 in your system, you will need to increase MaxSmartDrivers from 10 to 11 (if you have one TMC2660_BOB connected) or 12 (if you have two connected), and force numSmartDrivers to 11 or 12 in the startup code (normally it gets set to 5, 7 or 10 depending on what DueX board it discovers).

If you don't have a DueX in your system, then it would be simpler to connect the Step, Dir and CSN pins of the BOB to the corresponding E2 pins on the expansion connector instead of to CONN_LCD, and force numSmartDrivers to 6.

Danger

Thanks for the details. Since I'm largely on the right track, I'll give it a go using the expansion connector pins instead of CONN_LCD. I'll have to work the overlap with the BLTouch connections in place now, but that is workable.

Thanks!