Machine home zeroing with no motion from G code.

jodhner wrote:

Whoa, just lost my reply when I hit "submit". It said "Code not correct". I'll have to recompose my reply ...

Yeah, this site is all a bit flaky, but outside our control.
It's a good insurance to select-all / copy your reply before hitting the button.

Think you could sneak in a G code for no motion machine zeroing? G666?

jodhner wrote:

If the machine limit parameter is astronomical I'll just zero with G54, but my object oriented sensitivities will suffer.

The internal representation of the pulse counter is a long long, or signed-64.
At 200 steps per rev, and 8x microstepping it will wrap at 5.7 quadrillion revolutions (5764607523034234 to be exact)
You will find that your floating point representation of position gets a bit granular rather sooner, though. That is a double, so has 16 decimal digits of precision, meaning you will not be able to read the angle to less than 0.01 degrees after only about 30 billion revs.

I have looked at the code, and there is no way to zero the stepgen accumulator (which is what you would need to do) . Also, zeroing the accumulator would probably lose steps.

Dang, I was going to make an EMC2 based "Long Now 10,000 Year Clock", but I'd only get about 1000 years with a double.
Thanks for your time and expertise. I really appreciate it.

Think you could sneak in a G code for no motion machine zeroing? G666?

About 5 minutes after I left the computer I realized I may have misread your original question.

But it seems to me you may be able to do what you want in hal.

As your spindle is a open loop stepper..

Take signal going to your spindle and send it through a component with hal before going to the spindle drive.

Create a User Defined Commands such as M102, M103 use these commands to toggle the spindle signal on and off to the spindle drive.

So if stopspindlerotation = "no" the spindle signal goes to the spindle and if stopspindlerotation = "yes" the signal does not.

Insert M102 in your g code when you want to rewind your spindle without rotation.

Move the spindle to where you want in EMC without rotating it.

Insert M103 in your g code to turn the spindle back on.

RickG