Changing the step resolution in 7.7

[Alan Mclean]

I've blown a driver on an old CTC Replicator Dual clone (MightyBoard Rev E) and I'm in the process of replacing it.

The only "how to " I've found would leave the driver (A8944) set to a 1/16 stepping resolution.

Listing the Sailfish 7.7 file with ReplicatorG shows that it is set to 1/8 stepping resolution so I would have to edit the settings.

I have attached the the sections I think I need to edit but I'm unsure what to change, I'd very much appreciate it if you could look at them and post the appropriate changes.

Many Thanks aamcle

This is my situation (copied from facebook):-

I'm attempting to replace 1stepper driver on a Mightyboard with a A4988 to which I will solder the pins.

As you probably know the pins on the A4988 carrier board as fitted to a mightyboard are inverted, the chip is on the pin side of the carrier. Good fun that's were the potentiometer is going to be but that's another issue.

According to ReplicatorG Sailfish 7.7 directly references microstepping at a resolution of 1/8 so I'd like to set the driver to 1/8 stepping.

The only "how to" I've found requires that I don't fit the MS3 pin and bridge MS2 to MS3 with a blob of solder this will apparently give a resolution of 1/16 stepping.

Apparently for 1/8 I need :-

MS1 high,..... MS2 high,..... MS3 low ....... and if they are all high then I get 1/16 stepping

What would I need to do to set a 1/8 stepping?

So if I don't bridge MS2 to MS3 will MS3 be low?

Or I could ground MS3 with a short wire to one of the ground pins but that's a risk I might fry something.

[Rich Webb]

Well, there are apparently some leftover bits of older configurations still lingering in the corners of RepG.

If you run the numbers from the comment you get (8 ustep/step * 200 steps/rev) / (10.82 mm * pi) = 47.07 microsteps/mm. But the actual value in the XML statement is twice that at 94.14 microsteps/mm, indicating that the machine is expecting to use a 1/16 microstep.

Interestingly, a better value is 200 steps/rev * 16 ustep/step * (1 rev / 17 teeth) * (1 tooth pitch / 2 mm) or 94.12 microsteps/mm. The difference is in MBI's original estimate of the effective pitch diameter of the pulley. The small difference of about 2 parts in 10,000 is not significant in our applications.

What is significant is that S3G/X3G machines don't ever see raw distances. Those are in the gcode files but are translated to microsteps when the gcode is converted to x3g.

I think that the only place the machine actually uses the built-in value of microsteps/mm is when it clears the build plate to the bottom of the machine at the end of a print. Everything (?) else is commanded via the print's x3g file.

tl;dr: you want 16 microsteps/step.

[Alan Mclean]

Many Thanks

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