External stepper drivers instead of thermocouples on SPIO

MaracMB

Hello,
is there a way of having an option to use "spare" thermcouple SPIO pins on Duet2 or Duex5 or both... for step, dir, enable ? I know it is doable, since one member of my FB group has such thing configured with modified RRF v2..

Thing is, with rapid popularization of IDEX machines, the inevitable progress leads to IQEX. I have such a machine, but simple i3 style. 11 stepper drivers is all i need with it. Going further, evoluting to box design, 2 extra steppers are needed (dual Y and tripple Z opposed to one Y and dual Z in i3 design) while stacking dual markforged kinematics... Having two or even four extra ports for steppers would enable heaps of progress and tinkering.

Currently my workaround is demultiplexing steppers as there is always need for more... but honestly, demultiplexing isn't the most ideal; relying on additional modules, wiring, demultiplexer itself, much more complicated and slow toolchanging, addtionaly required simple "closed loop" addons like s42b with custom firmware to have a factored steps for each module and forcing enable while module is not selected with mux... just overcomplicated.

While we could just use those pins and have extra external stepper pins available on board(s). Or at least Duex5 since we are all drooling for accelerometers...
Also, it would position duet even further ahead of alternatives...

Thank you for your consideration.

dc42

The firmware is written to assume that all STEP pins are on Port D. The SPI CS pins are not on port D. However, EN10 (aka CONN_LCD DB7) and DIR_10 (aka CONN_LCD DB5) are on Port D. So the simplest way to add 2 more drivers would be to use those as the extra STEP outputs, and reassign the original functions of those pins to spare SPI CS pins. Then recompile the firmware with those changes and the extra drivers.

In the medium term, the most straightforward way of achieving this would be to use two Duet 3 Mini boards in master-slave configuration, each with a Mini2+ expansion board.

MaracMB

@dc42 thank you for fast response. I am looking for 13th and 14th (or even 15th and 16th) stepper driver so not existing expandability options within duet2+duex5. So not exactly what i asked but I'll settle for this kind answer.

Duet 3 mini with expansion would give 7 stepper drivers each, so 14 needed, but i do have to read up if this would also have 8 channels of PWMs for fans, five heaters + at least 1 PWM for bltouch/probe and stuff that is needed to drive one proper IQEX...
I'll have to read up but ain't thrilled on going anything mini. It's just the ordinary "go duet3" way then OR doing an addon PCB for multiplexing.. Ourighty then.