rotary vs linear axis homing (or not)

Started by matthewdc on Oct 17, 2017 in TinyG Support. 1 reply, last activity Oct 17, 2017.

matthewdc Oct 17, 2017 #

I have a rotary axis with a homing signal that I want to use. As opposed to what the wiki says about homing, the limits may be unnecessary, but I usually WANT to home or I don't know what angle it powers up at.
Anyway, I'm having goofy results trying to use homing here.

The homing signal from this stage is a true homing-style switch: not a blip but always ON with half of the rotation and always OFF with the other. That way the control automatically knows which direction to go to hit the homing switch (this also applies to linear stages with a homing switch somewhere in the middle).
I've got it rigged up to work with the existing G28.2 a0 command but it always does a full 360 with a pause/buzz at the 180 degree point.
I'd like to write my own homing routine but I don't see that flexibility with TinyG.
I also want to use the limit switches to prevent out-of-range motion but not kill everything and requires a reset! The program would stop executing but the position would be retained and allow backwards motion but no motion further into the switch. Am I pretty much stuck with this?
thanks

cmcgrath5035Staff Oct 17, 2017 #

I sort of follow your discussion above.
First, see my comment in your other post, what I read says setting min=max=360 degrees is equivalent to shutting off limits, but not clear from your description that is what is happening either.

I believe your switch action is not what is programmed into tinyG fw. You have both A switches set $asn=$asx=1, homing.
Only one should be set =1, you home to min or max, not both (or either).
TinyG homes on a transition, either low-high or high-low, based on $st setting, NO or NC.

You could fork the firmware and rework the C code, if you want.

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