Re-homing fails in axis sim

[BsAtHome]

Running 2.10-pre directly from git master on Trixie.

A repeatable way to fail homing was discovered resulting in the message: Cannot home while shared home switch is closed j=2.

Scenario to repeat:

1. Start axis sim and set Estop=off, Machine=on
2. Home all axes (press "Home All" button) and wait for all axes to be homed
3. Unhome all axis (menu "Machine/Unhoming/Unhome All Axes")
4. Again try to home all axes (press "Home All" button)
5. --> error pops up

Other scenario to repeat:

1. Start axis sim and set Estop=off, Machine=on
2. Manually home X (menu "Machine/Homing/Home Axis X")
3. Manually home Z (menu "Machine/Homing/Home Axis Z")
4. --> error pops up

Manual order homing Y, Z, X in second scenario does work, but you still cannot unhome and repeat the homing as in the first scenario.

[Sigma1912]

That is because we have 'HOME_IS_SHARED = 1' for joints 0 and 2 in the ini file.
To rehome you need to move the X axis in the negative direction so the simulated shared home switch signal goes False . Not sure if this ever worked otherwise but this could probably be fixed by setting 'HOME_OFFSET = 1'
https://github.com/LinuxCNC/linuxcnc/blob/master/configs/sim/axis/axis.ini#L172

[andypugh]

Yes, this is a long-standing irritation with the Axis sim. I have often found it when trying to debug other things, but have always been more interested in the other thing....

[hansu]

The same for the gmoccapy sim configs. At least when you abort homing and try to re-home.

[BsAtHome]

Setting HOME_OFFSET of JOINT_0 to 1.0 does indeed solve the immediate problem. But you can still trigger the problem.

So, why is there a shared homing signal? Is this necessary for the sim? I can see an application in real machines, but in a sim?

[Sigma1912]

I don't think it is necessary. It may just be like that because somebody found a way to simulate it many years ago.
https://github.com/LinuxCNC/linuxcnc/blob/master/lib/hallib/simulated_home.hal

[andypugh]

I imagine it is to demonstrate the concept.
However, with a real machine you would be able to see which axis was on the home switch / end stop. With the sim it's a bit mysterious.