reprap dc42 config.g end stops active low and active high, relative and absolute coordinates for multiple extruders

Can anyone help is it possible using the config.g to

A) set a single end stop to be active low for Z, while the rest remain active high?

is it possible to set specific extruders to use absolute coordinates while another remains relative?

If so what are the commands, i cannot find the answer on reprap wiki.

If not what would you recommend?

Thanks

Dave

To set the Z endstop to active low and the X and Y to active high, assuming all of them are at the low end of the axis:

M574 X1 Y1 S1
M574 Z1 S0

But is it really an active low Z endstop switch you have, or is it a Z probe? It's very common with Cartesian printers using RepRapFirmware to not have a Z endstop switch at all and to use the Z probe for Z homing. To specify an active low Z probe connected to the E0 endstop connector, use:

M574 E0 S0

There is currently no provision for having some extruders using relative coordinates and and some using absolute. What would be the use case for such a configuration?

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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].

My only guess as to the use-case for the different extruder schemes, it might be to manage a paste extruder or other finite-distance extruder and perhaps put a soft limit on the max value as to prevent damage to the paste extrusion system, or to allow more convenient refills. Having a dual-nozzle set-up, one PLA, one paste, is actually a goal of mine in the not-too-distant future.

Edited 1 time(s). Last edit at 11/08/2015 09:40PM by n8bot.

Hey, thanks for your reply, I was on a long weekend break.

I am currently working on a mod for your firmware to control 6 axis, ie rotation around X Y and Z. But I am migrating from marlin to the duet as there is a little more head room, also the drivers are a ready integrated into the hardware. I have been asked to keep modifications to a minimum (to save time and cost mainly). The printer I am working with is a modified Prusa i3. I could change the location of the Z endstop so it's active low like the X and Y stops, but I have an advantage of collision detection with the way it's currently set up (Active high, an Active low Z endstop switch that is being used as a Z probe (where the hotend would touch the bed and release/activate the switch)).

With regards to the relative coordinate for the extruders, I'm curious to see how much work it would be to have them working like the x y and z drives, but perhaps it would be easier just to parse the gcode in my software suited for your fork?

I realise that this has already been attempted/achieved via a masters student from the University of Oslo, I am not sure if he has released his code (open source) or not; I cannot seem to find it.

Thank you,
Regards,

Dave