[Grbl_Esp32 PR#234] Homing set machine origin to bottom left

#1 – bdring 于 2019-09-27

@cprezzi We have some pull request guidelines. We like to target the devt branch with all new changes. This allows a little more public testing and makes it easier to merge if we all target that branch.

I would also like a little more background on the purpose of this change and why you feel it should be enabled by default.

#2 – cprezzi 于 2019-09-27

I’m sorry, I didn’t see/read the pull request guidelines. I will correct my request and add it to the devt branch.

The homing logic of grbl (machine in negative space) often causes problems on maker machines, because the usual expectation is, that the machine origin is on bottom left (like in Inkscape) and not on top right (as grbl default).

The flag I have added does exactly that. It sets the machine origin to bottom left after a homing sequence, independent of homing location. For example, when homing to top right ($23=0), it sets the actual position to max. X and max. Y, which means bottom left gets 0/0.

I think it doesn’t make sense to activate this flag by default. It’s probably better to have it commented out by default, so nothing changes.

#3 – bdring 于 2019-09-27

I am OK with it if it is not the default.

I am not a fan of implying any type of significance to values in the machine coordinate system. A person, especially a newbie, is unlikely to ever use MPOS. The sooner a new maker understands that, the quicker they will master their machine.

The one exception I often use is a rapid move to the top of Z axis to access the spindle. I use a G53 macro to do that. The Z typically homes in a positive direction, so I don’t think this changes that.