Linuxcnc not seeing limit switches

Have an ancient Bridgeport CNC mill. Removed ALL the electronics and replaced with PC, couple of PMDX bob's, and Gecko's.

This old beast runs fine, when it runs.

But lately, when I ask it to start up and home the three axis, it runs fine, but NEVER finds the limit switches. This prevents it from setting the three axis to zero.

I've been fighting this battle for a while, and I'm stumped.

Has anyone written a good trouble-shooting procedure for tracking down problems like this?

Thanks

Tom

What type of limit switch are you using?

Can you manually trip the switch without moving the table? If so open Halmeter and pull up the pin that corresponds to the input where the limit switch is connected. Manually trip the limit switch and see if the state of the pin changes.

If the pin state does not change, make sure the switch physically and electrically works, make sure the connections are made correctly. The diagnostic process here will depend on the type of limit switch you are using.

If the pin state changes then make sure your .ini file is configured for homing properly. Also check that the HAL file has the pin netted properly to the home switch.

The limit switches are the factory installed Honeywell micro switches, although one of them has been replaced, as the original was getting stiff from age.

I can reach and activate the X & Y switches by hand, but the Z switches are inside a cover.

And this configuration is the same one (I think) that has ben running fine for a couple of years. This is just a new trick its learned.

I have a Hal display (not sure what to call it) on the screen at all times. It's showing the X switch closed, and the Y and Z open.

But I'll go through your process, as what I've been doing has stopped working.

Thanks

Tom

Since they are micro-switches you can check for mechanical and electrical function by probing the pin connections on your BOB with a multimeter set to read resistance. It should read open circuit with the switch in one position and closed, zero resistance, in the other position. If this is working at the BOB then it is either somewhere between the BOB and computer or the .ini and Hal files are not configured properly.

Since from your original post I am assuming that none of your home switches are working the I would think it would be something in the .ini and Hal files that changed.

I doubt that all of the switches lost connection at once or physically broke.

I have a Hal display (not sure what to call it) on the screen at all times. It's showing the X switch closed, and the Y and Z open.

That is interesting. Is the one that was replaced the X switch? Why is it different from the others? Are these combined limits and home switches?

The Y was replaced with an identical switch, and it has worked since then.

Haven't put an ohmmeter on the switches, but with the whole thing powered, I do go from 0 bolts with the switch closed to around 3 volts or so with the switch open.

Gonna start hunting through the ini files, etc tonight.

Thanks again

Tom

Unless you have changed something in the INI and HAL file - that is the last place In would start looking.

Check with HAL meter if the switches change state when toggled.
I would some of them won't.

Chris M

I agree with Chris. The first thing to check is if the HAL pin for the input changes when the switch is manually tripped.

If the HAL pin changes when the switch is manually tripped, then start looking for configuration issues.

I haven't changed anything in the ini files

BUT

I've had hard drives crash on two different computers at the same time. I THOUGHT that I had stored the working ini files on a thumb drive, but there's no way to verifiy that.

Looks like I need to get my pipe and my Sherlock Holmes hat out and do lots of sleuthing.

Thanks

Tom

It occurs to me that not only have I changed the hard drives and motherboard (old rig was IDE, new is SATA) but I've also changed the parallel port card.

Ran the lspci utility, but I'm not able to identify the port addresses. This appears to be the applicable section, but I could be wrong...

04:00.0 Memory controller: NetMos Technology PCI 1 port parallel adapter (rev 01)
Subsystem: LSI Logic / Symbios Logic Device 0010
Control: I/O+ Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Status: Cap- 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR+ INTx-
Interrupt: pin A routed to IRQ 17
Region 0: I/O ports at 1010
Region 1: I/O ports at 1018
Region 2: I/O ports at 1020
Region 3: I/O ports at 1028
Region 4: I/O ports at 1030
Region 5: I/O ports at 1000
Kernel modules: parport_pc

Attached is the complete file.

Can someone help me decipher the actual port addresses for both parallel ports?

Thanks

Tom