Homing problems on Z-axis

Gents!

First off - i'm a total newbie to LinuxCNC but have been dreaming of owning a cnc mill for nearly 20 years.
So finally - I recently purchased a chinese 3040 mill/router and couldn't be happier.
I thought of it as an fast and cheap way to get started and learn something about this wonderfull world.
Before doing any actual work on it i installed and configured home switches on all three axis.
"Home" is set to be front left corner with Z all the way up - and got it working like a charm!

But this morning when moving the machine to a temporary box/enclossure something happened and i can't figure out what went wrong.
First of all the z-axis moved the wrong way i got the message "cannot unhome while moving joint 2" which i traced down to a broken wire on the Z-axis home switch.
But even now, with the home switch working again, LinuxCNC does not recognize it when homing.
It just moves past it and rams the z-axis right into the top - Not a nice sound, i might add!
The home switches are all installed in NC mode and break the connection when triggered.
I can meassure the home switch breaking when the z-axis hits it, but this does not stop the axis from moving.
Only pressing F2 prevents the axis to hit the mounts but then i again get an "Cannot unhome while moving, joint 2" message.

My guess is that the the home switch signal is not received by LinuxCNC (damaged break-out board?), and to verify that i would like to learn about a method to read the input signals real-time.
Meaning seing the home switch signals change real-time.

I have tried using HAL Scope without succes,- that is, i can see the signals, but they don't change real-time.
I would be very happy if you could help me out here.

My ini file for this axis says:

Hal file for axis 2 says:Any suggestion would be greatly appreciated

Best Regards
Jesper

Use the halmeter to check your home-z signal, while triggering the switch manually.

Halscope is good for fast changing signals, but halmeter is better for simple checks or slow changing signals.

See section 3.6 of linuxcnc.org/docs/html/config/ini-homing.html#_home_offset
Your ini would indicate that the homing switch is at the bottom limit of travel. If that is the case, it might be that it is searching for the switch but not finding it because it has already passed it. If that is not the case, you need to adjust the home_offset value.

Your HOME_OFFSET value looks to be wrong, although if it was working beforehand maybe it's not the issue. The description for HOME_OFFSET in the documentation states that:

The home switch location, as indicated by the HOME_OFFSET variable, must be strictly within the soft limits. That is, MIN_LIMIT < HOME_OFFSET < MAX_LIMIT.

What happens when HOME_OFFSET is the equal to the MIN_LIMIT value (as you have in your INI file) isn't clear, so perhaps LinuxCNC just ignores the value set in HOME_OFFSET and homes Z as if it had no offset. Ie, your previously-working homing of Z-axis perhaps only worked by pure chance.

I'd be more focusing on the reason as to why you can't see the limit switch being triggered manually in Halmeter or Halscope. If it was previously working and you've since discovered issues with the wiring of the home switches on that axis since the machine was moved, I'd be looking at more wiring or circuitry issues on that axis' limit switches.

Thanks,- exactly what i need!
Ill be looking into that and figure out how to use it
Br Jesper

Good point about the home offset
Actually i figured out what the problem was just when i went to bed,- and it was far worse than a broken cable.
When disconnecting the machine to put it in a box, i did not have the common sence to just unplug the plug from the breakout board.
I actually unscrewed all...
And then - the next day putting them back in - i put the common ground to all three home switches into an unused input port - and not in the ground port - in essence leaving all home switches floating.
So the problem was my mind not understanding what my eyes where seing.
Worked just like supposed again
Br Jesper

Yes - actually i was able to jog Z both up and down, and in the direction that i wanted.
The error message ("cannot unhome while moving joint 2") itself actually hinted that the link from the home switch was broken.
I just failed to see that actually all three home switches where triggered as being active - since i didn't know how to use HAL meter

/Jesper