Homing failure only on Y axis

I need a little advice please.

I have an XYZ home made router running Axis 2.8.2-11-g6a3d0a434 through the parallel port, which has been running fine for some while.

Yesterday morning I went through the usual initialisation - Home all, set XYZ etc cut a part and all was well. I quit LinuxCNC and shutdown the PC in the 'proper' way.

Last night I went to cut another part and during the Home all process the Z homed OK, X homed OK but the Y started to home in the opposite direction for no apparent reason.

The Keyboard moves the Y axis both directions so it's not a DIR wiring connection failure.

I've tried Restarting LinuxCNC, rebooting the PC, tried running StepConf again and saving, running StepConf making a minor mod and resetting the mod and saving - all with no change to the Home All Y direction - still wrong.

My last resort will be to rebuild the software as I guess there's a bit changed somewhere in the software changing the direction of the Y home movement.

Can anyone suggest what else I can do to determine the fault, any checks to make or any other actions I can take please? 
I like to know what caused the problem so I know what to do/look for in the future if this happens again.

Thanks in advance
Cheers
Barry
 

Additional information:

XY&Z have a single switch on each axis for Limit & home functions
Barry

Hard to say. But things like that usually don't change overnight. The direction of initial search movement during homing is set in the ini file in your config folder.

Hi Tommylight
Thanks for both of your replies
I'll look later today to see if there's any change in the .ini files (got family coming today so wife 'suggests' that's a higher priority )
I didn't open the calibration menu at the time or anything else, I just shut the machine down as usual and found the issue when I restarted it.
I have opened the calibration menu when I was trying to discover anything I could find to get back to 'normal' but I don't remember changing anything as I couldn't see anything relevant.
Thanks once again, your reply gives me a starter of what to look for.
Cheers
Barry

Many thanks to all for their help.

Well that's a strange one

Convinced it was a software issue I installed another HDD & loaded V2.8.2 only to find the same thing happened. Not a software fault.

Ran stepconf, changed the Y Home switch velocity to a + (was a -) and the Y axis moved in the right direction BUT it didn't stop at the limit switch.

THE FAULT WAS A JAMMED LIMIT SWITCH !

Analysing the issue, during Y homing the system thought it had reached the limit and was backing off waiting for the switch to become false, which because it was jammed, never happened and so travelled to the opposite extreme.

Resetting the config, unjamming the switch and manually operating it I was able to replicate the 'fault' proving the solution to be correct.

Phew that's a relief

Cheers
Barry

You should get the error when you turn the machine on that you are on a limit switch. It should not allow you to turn the machine on.
And you definitely shouldn't be able to jog with the machine off.

Thanks tommylight,
Just checked this on my machine.
I am not an expert so I may be using the incorrect terminology (apologies) and my machine may not be set up in a ‘proper’ or conventional way, I am a lone, self taught user with a machine that has worked fine for me for quite a few years.
My setup has 3 switches, one on each axis. In the parallel port setup I declare the 3 switches are Home X, Home Y and Home Z, with no reference to Limit functionality. Thus I have what I believe to be soft limits where the minimum limit is the home switch and the max limit is home + specified travel for each axis.
When I power up in a random position and Home all each axis homes Z then X then Y as expected. If I Home all again I get a prompt Re-home? Each axis then moves away from the switch then moves towards the switch then backs off a bit (technical term )
It’s this latter functionality that caused the problem I first highlighted since the Y switch was permanently active. The Y axis moves away from the Home Y switch (until it became false) and since it was jammed on it kept moving away until it released (which it never did).
To answer bevins,
I do not have any limit switches only home switches as described above. That seems strange to me anyway, if it is on the limit you are saying that the machine will not turn on? Then how do you move it off the limit to turn it on – it seems like a catch 22 to me on the limit so can’t turn on, but can’t turn on to move it off the limit??
Agreed when you say “and you definitely shouldn’t be able to jog with the machine off” I didn’t say that.