hi all,
ok so i've been looking around and the practice of creating a "modular" 3d printing electronics board is extremely common, thanks, many years ago, to the stupid, stupid decision to use prototyping (evaulation) plugin boards with 1.3 to 2.0 *amp* stepper ICs mounted onto micro-postage-stamp-sized PCBs. the problems these cause are endless.
*some* people have actually read the datasheets associated with these driver ICs and have designed PCBs that respect the advice of the designers, by making sure that a large part of the PCB's copper is used as a heat-spreader. however the practice is not very common, and the people who make such boards are typically actual well-trained electronics engineers from the west, but who then use western PCB manufacturing and assembly plants, end result: very expensive boards ($120 to $200).
as i would like to see both a low-cost board made *and* have a decent design, and having researched this for many weeks and found that what i am searching for DOES NOT EXIST i need some help. the board i believe is best started from is the Duet WIFI: https://github.com/T3P3/Duet
this uses 2.5A TMC2660 "silent" steppers and importantly they're SPI-based. the idea is to cut the DuetWIFI down to the *absolute* bare minimum, turning it into the exact same thing as TRAMS (which uses the 1.3A TMC5130).
so instead of an on-board ATSAM4, you use an arduino due. instead of WIFI you use a *standard arduino WIFI shield*.
now, debatable is whether to split out the MOSFETs, endstops and thermistors into their own separate shield as well, which i feel might be sensible.
in particular i would very much like to "stack" the steppers because i have a design where it is going to use *four* z-axes. in a first iteration those may be wired up as 2x 2-serial in parallel, however it would be very *very* nice to be able to just add a second "stack" of 4 z-axis steppers and use them to do automatic bed-levelling. so to do that it would mean having on-board jumpers that could select alternative GPIO pins... or maybe to use an I2C-based or SPI-based GPIO expander in order to reduce the amount of GPIO needed.
however an alternative idea which would do just as well (without needing too much work) would be to have the expectation that there would be a "base board" into which *two* modular 4x TMC2660 stepper boards would be plugged, and an arduino due, *and* the MOSFET/endstop/thermistor board, and the *base* board would take care of GPIO expansion.
anyone considering this: the layout on the DuetWIFI for its steppers is very *very* specific and should really not be touched or altered, merely cut away surrounding parts and add the necessary arduino-compatible headers.
any takers for what is likely to be a quite straightforward project?
l.
--- crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68