Add Support for Dogbone Homing

[sundtek]

I'm retrofitting my Mitsubishi Meldas M65 based CNC, the homing switches are dogbone style switches.
The axis first approaches the endstop bar at coarse speed, then switches to a fine homing speed once the switch is triggered. When the switch is released again, the controller registers the axis as homed.

I have tested this behaviour with Linuxcnc 2.9.8

This patch introduces a new option HOME_DOGBONE = [bool] for the [JOINT_n] section. Default = off

[hansu]

What are dogbone style switches?

[BsAtHome]

What are dogbone style switches?

If I understand it correctly from the PR description... The homing switch is of assert/deassert type, where you "roll over the switch" and the deassertion is the exact home position.

So, move v_coarse towards home until the homing switch activates and when it does, continue direction but reduce speed to v_fine until the switch deactivates. However, the code does not do the high/slow speed transition afaics. Or does it?

[mozmck]

It's there in homing.c line 878-885.
The logic looks good to me. The only small issue I see is that I think any custom homing components will have to be updated for the extra home_dogbone variable as was done in homecomp.comp
Not a big deal I don't think and it probably won't affect many people but it does me as I have a custom component to improve dual gantry homing.

[BsAtHome]

It's there in homing.c line 878-885.

Check, thanks.

[grandixximo]

There are also components for ethercat deferred homing floating around, those will need update as well if this lands?

[hansu]

What are dogbone style switches?

If I understand it correctly from the PR description... The homing switch is of assert/deassert type, where you "roll over the switch" and the deassertion is the exact home position.

So, move vcoarse towards home until the homing switch activates and when it does, continue direction but reduce speed to vfine until the switch deactivates.

I understand the loigic, but I wonder how the switch looks like and if it's a common name for that because I have never heard of that and also cannot find anything about that notion.

It could look like this

[hansu]

Further it would be good to add documentation about that in https://linuxcnc.org/docs/html/config/ini-homing.html

[grandixximo]

If I understand correctly this should be incompatible with managing homing+limits with the same sensor, correct?
[HOME_IGNORE_LIMITS] = TRUE will be a bad flag to have when using this style of homing??