Axis motion limit switch configurations

I have done programming for scanning systems, 3 axis. Long ago enough this was by means of rs232 into a dedicated motion control box. Certainly not cnc. Nonetheless the were home and CW & CCW limit switches on all 3 axis. In he cases each limit switch was independently wired. As the controller box provided jogging control, if any limit switch was hit, motion in that axis was stopped, but only in that direction, you could use jog to back off the limit. The other axis could still jog. I see some configurations for linuxcnc where all limit switch just return to one pin. Does not seem very nice. I am questing that leaves it to the operator to manually back off.

That froze all axis! I guess that comes down to enough interface / gpio pins.Is linuxcnc then generally, by software control, just stop brute force all stepping functions on all axis? Abruptly? Does it allow decelerating, by option, if there is enough spacing between hitting the limit and the mechanical crash?

Is there a specific place in documentation that addresses these issues?

Thanks, Stan (a new guy)

You can wire limit and home switches in a multitude of ways from one input for all functions to one input for each function.
Typically there is a screen button that after pushing allows you to move the offending axis.

In linuxcnc you should never ever hit the hardware switches other then homing.
Linuxcnc knows where you are after homing and will not let you past 'soft' limits.
It decelerates when coming to these limits.
There are simulated machine configs you can try.

Chris M

If you follow the links to the documents on the LinuxCNC home page to this:
linuxcnc.org/docs/
Then choose the Current stable version or Development version. Look for the configuration heading and work through that. the Homing Configuration chapter is probably the most important and it is handled differently in each version.
I have a gantry machine and I have seperate limit switches on each axis. On the Z axis due to space constraints I use a shared home/limit switch and I found this one more difficult to configure initially (You need to use a HOME_OFFSET to move the axis off the home switch during homing otherwise you will get a limit switch error as homing completes.

Thanks for the replies. The documentations has improved a lot from when I looked briefly into Linux a few years ago. Wow. Configuration seems to be more automated or programmed.

I have searched for the source code itself but only find snippets and mods. I am sure that it is imposing, but would like to see the fast loop components. Where can I find the main set of source code?

Stan

Stan,
Source is in git hub here. github.com/LinuxCNC/linuxcnc
Master branch = development branch. The stable 2.7 branch shows up as a separate branch in the drop down. The individual components (for master) are here
github.com/LinuxCNC/linuxcnc/tree/master/src/hal/components

Back in the docs, there is documentation on how to write and install your own components (.comp files) under the main head HAL (Hardware Abstraction Layer).

The main trajectory planer code is in the src/emc folder.