Homing A axis (I have a sensor for it)

I can't seem to find info on how to configure my 4th axis to support homing. I have a sensor for it, but it's not clear how to configure linuxcnc so that I can do an homing operation (the 4th axis isn't always installed), and also not trip just because the index went by the sensor.

What's the config to achieve this?

I also have a detachable 4th axis. To manage homing correctly I have a hal-signal that defines whether the 4th axis is present or not. If it is present then it homes normally as setup in the ini if it is not present then I generate a homing pulse in classicladder to home the axis as soon as it starts the homing process.

I can switch ON a fourth axis, normaly not plugged in. So homing is normaly set to no=0. In csse i use this axis i simply press homing-a in gmoccapy

Or you twi different projects.

To answer my own question: it seems it works as desired to simply configure homing, and to specify only a home switch input on the joint:

As to avoiding the need to home when the axis is not present, I'll have to do something like what Aciera suggested, although I really don't want to.

Update: I was wrong. I wish there was a way to tell LinuxCNC to ignore an axis for homing at run time (e.g. via user interface, or some signal the hardware can detect).

Or think the other way round...
This axis will never be homed automatically.. =0
Use a special button to home when you want nevertheless.
Gmoccapy can do so.
Mike

If you omit HOME_SEQUENCE the joint won't be homed via home all.

My A-axis is not in my home sequence.
And my A axis is not always fitted.

I don't actually see that much is gained by homing the A axis, as the workholding that fits it all allows the work to be mounted at any angle.

I suppose if you are in the habit of turning the machine off with part-finished work in the rotary axis then there might be some point.