I’m interested in homing to zero instead of positive limit, because I typically load my work near machine zero and at 780 x 1280 working area, it would be annoying to have to traverse the whole table to cut something small near x0, y0 which is the general area where I normally park the spindle. But reading the grbl config documentation I don’t see configuration to allow that. Am I missing something?
Yes, I read too fast. $23 is what I want.
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Be aware that homing just sets the machine origin and you can set the work origin wherever you want. Just use G92 to set the work offsets.
Yup! I just wanted it to know about max size so I don’t accidentally go past the X/Y max. 
G10 L2 P1 Xxx Yyy will permantly set a work offset to where you want it. I’d have to look up the exact G10 command i used todo this with a grbl controlled laser. Home takes the head to the rear left corner. i want 0,0 to be the front left corner so I always work in positive coordinates. G10 was my friend.
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Ah, but the point here was that I wanted home to take the head to the front left corner because that’s where I work, and 780x1280 working area would be a long homing cycle. I installed my limit switches to support homing to the front left corner (working in the 1st quadrant) and just wanted to configure for homing to those limit switches, so that soft limits of 780x1280 would avoid accidentally driving the head against hard stops if my WCS is offset more than I intended.
I had seen $23 before and remembered only that it was possible, not the name of the configuration value. Then I missed it on re-reading, thus the question. Then I found it again, thus answering my own question. 
With $23=1 my OX homes to the front left.
However, I didn’t know G10 before so I am glad to have learned this today! Thank you!
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