New control board - Eliminating hardware jumpers for stepper drivers

Hi all,

I'm in the process of designing a new controller board for a new printer that I have designed.

Somewhere along the line I decided that I wanted to eliminate the need for hardware jumpers, and to control the micro-stepping setting with software and some nifty i2c ICs.

Assuming 8* stepper motors, a combination of 3 pins on each stepper driver to be grounded for the desired micro-stepping setting, a total of 24 pins would be required to be grounded.


Does anybody have some recommended ICs which would be fit for this purpose?


Thanks

Jumpers are cheap.. and you hardly ever change them.

Why would you waste money on obscure hardware that will for most people never be changed/used?

Also if its not a 32bit controller, please don't waste your time.

Now after saying that...

what about 2* Microchip MCP23017 eg [tronixstuff.com]

I'd suggest keeping the controller separate from the power electronics, so 32bit vs 8bit controllers isn't an issue.

Connecting between the controller and electronics boards could be done via I2C.

I disagree. Processors are very cheap (at least the 32-bit ones are) so if you separate the boards, you risk spending more on interconnect parts and expensive tbrough hole component assembly than the processor and supporting components. I2C is OK for a few functions on printer control electronics such as setting stepper motor currents, but far too slow for driving the stepper motors.

Nobody uses less than 16x microstepping so jumpers are not needed when using A4982 or A4988 drivers. With DRV8825 drivers, there is a weak case for allowing switching between 16x and 32x.

Edited 1 time(s). Last edit at 10/16/2015 03:50PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

What if you only control the MS3 pin of the drivers? You could pair X and Y because they'd be the same anyway. Z ( 1,2 ) and E (1,2,...,n ) would also require only one bit each.
That way, the user can choose between 1/8 and 1/16, which is more than enough. But you still need only 4 pins ( or 4 bit I2C register )
-Olaf