UGS and limits and alarms

I’m using an SO3, and working on switching from Carbide Motion to UGS for touchplate and WCS reasons. I’m using gcode produced by Fusion 360.

I noticed that UGS would happily try to drive past the ends of the rails, so I enabled hard and soft limits in grbl ($20 and $21) and adjusted max travel settings so it couldn’t hit the rails.

Everything homes fine, I set 0s successfully, but when I start running a file the machine first tries to go home, where it hits the homing switches and goes into an alarm state (leaving a running router with the motors disengaged, which is a little scary!). Using the same gcode files CM does not go home first, when running the files, so maybe that’s a UGS thing?

Anyone have experience with UGS, homing switches, and limits, who can tell me which combination of limit settings will both prevent crashing into rails and also not alarm at the beginning of jobs?

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In case anyone else has this question in the future, the combination that worked well for me with grbl 0.9 and UGS 1.0.9 was:

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I’d encourage you to try the 2.0 version of UGS. I recently updated it to work with the oddball version of GRBL that ships with the SO3, there are some new touch plate features in the “platform” version (I’ve been meaning to add corner-plate probing but haven’t had much time for hacking lately).

As far as what UGS does to help with Limits… pretty much nothing because GRBL supports these things natively (as you’ve already figured out). I’d like to add more WCS now that I’ve started using them, but haven’t had the time.

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Oh cool, I didn’t realize the newer versions of UGS would work with older grbl. I’ll give it a shot!