EMC2 & Limit Switches

[acondit]

Can anyone help with info on setting up limit switches in EMC2? I have read what I thought were the relevant sections of the integrators manual but can't seem to find anything useful.

I am using a CandCNC mini-io bd. I have installed a roller arm micro switch at each end of my X, Y and Z axii. I have wired them in series NC (normally closed). I am planning to connect them to pin 15. Then when I install the home switches, I plan to connect X to pin 11, Y to pin 12 and Z to pin 13. My Estop is connected to pin 10. (The mini-io bd uses the xylotex pinouts.)

What I really need to know is how to name what they logically connect to?
For example the estop (pin 10) connects to "iocontrol.0.emc-enable-in" like below.
linkpp parport.0.pin-10-in iocontrol.0.emc-enable-in

So if I have it right so far, then the limits would be --
linkpp parport.0.pin-15-in iocontrol.0.??????
X home would be --
linkpp parport.0.pin-11-in iocontrol.0.??????
Y home would be --
linkpp parport.0.pin-12-in iocontrol.0.??????
and Z home would be --
linkpp parport.0.pin-13-in iocontrol.0.??????

Thanks in advance for any help.

[andy55]

EMC's HAL interface is described here:
http://www.linuxcnc.org/docs/html/co...hal/index.html

in EMC2, iocontrol is only used for non-RT stuff, like coolant etc. so the pins you want are either in motion., or in axis.

AW

[acondit]

AW,

In the example for connecting E-stop, they show e-stop being in io-control. That seems to me to be as time critical as limits. What am I missing?

[andy55]

Originally Posted by acondit AW, In the example for connecting E-stop, they show e-stop being in io-control. That seems to me to be as time critical as limits. What am I missing?

an E-stop signal is indeed connected to
iocontrol.0.emc-enable-in
and it runs in userspace, i.e. non-RT.

The idea here is that you should _hardwire_ that same E-stop button to control the powersupply etc. of your motors/spindle. On big machines there would also be brakes on the axes/spindle to halt motion.
This way your external E-stop button will still do it's job even if your computer has crashed or is unresponsive.

So, when you press E-stop, motion immediately stops, and EMC is informed of this pretty quickly also, but not in realtime.

AW

[acondit]

Andy,

Thanks. I looked in the link you gave me and I still don't see what pin names I should use for the limits.

For the home switches:
It looks like x-axis home should be:
linkpp parport.0.pin-11-in axis.0.home-sw-in

y-axis home should be:
linkpp parport.0.pin-12-in axis.1.home-sw-in

z-axis home should be:
linkpp parport.0.pin-13-in axis.2.home-sw-in

Are these correct for my home switches?

[andy55]

your idea for home-switches looks ok.

It looks like you've found a documentation bug. Congratulations!
Documentation is one area where non-programmers can help an open source project a lot ! (wink, wink)

what you are looking for is probably
axis.*.neg-lim-sw-in and
axis.*.pos-lim-sw-in

in the meantime, you should learn to use all the HAL tools available, for example with halshow you can see all the available pins. The names should mostly be self-explanatory
http://www.linuxcnc.org/docs/html/ha...how/index.html

AW

[acondit]

Andy,

I am also a developer, but I have to get my feet wet and understand stuff better before I try to do any coding.

Thanks,

[acondit]

I got some help from John Kasunich. He said that I needed to create a new signal and connect it to the parallel port pin that I wanted to use and then connect the signals for each axis-limit to that signal. I tried it and it worked.
Here is the configuration that I had to add to the file "xylotex_pinout.hal".

# create a signal for the combined limit switches
newsig on-limit bit
# connect it to the parport pin
linksp on-limit parport.0.pin-15-in
# connect it to all of the motion controller limit inputs
linksp on-limit axis.0.neg-lim-sw-in
linksp on-limit axis.0.pos-lim-sw-in
linksp on-limit axis.1.neg-lim-sw-in
linksp on-limit axis.1.pos-lim-sw-in
linksp on-limit axis.2.neg-lim-sw-in
linksp on-limit axis.2.pos-lim-sw-in

Thanks to both Andy and John for their help,
Alan

[acondit]

I am running Axis as my interface. Now the limits are working but when I drive an axis into the limits, and try to bring it off of the limit switch, the machine power button is dimmed and I can't bring it out of Estop. It seems like the minute that the limit switch clears, something is being disabled and I can't clear it.

If I edit the config and use the original Estop loop back it works fine, but it doesn't like having the real Estop switch enabled. This is what I am using to enable the Estop switch.

linkpp parport.0.pin-10-in-not iocontrol.0.emc-enable-in

Pin 10 is pulled high and goes to one side of the Estop switch, the other side of the Estop switch is connected to ground. The switch is closed when out and open when you hit the Estop. I measured the voltage after it quits working and with the switch open it only measures 0.89 volts. It is like pin 10 is being pulled low by the pc rather than functioning as an input pin.

Help!!

Alan

[acondit]

I replaced the first mini-IO board with a spare that I had and everything is working.

It seems that the opto isolator in my first CandCNC mini-IO board went south. I called Tom at CandCNC and he said send it back he'd fix it. I really appreciate the great service from CandCNC.

Alan

[acondit]

I re-did my limit switch loop. I was getting three error messages when I ran into a limit because as far as it was concerned I had hit all three limits at once. Now I only get a limit message for the appropriate axis.

I separated it into 3 loops, one for each axis. So each loop has two switches. On each axis I use one of the switches as both a limit and home and the other as just a limit. EMC2 supports this in software. It ignores the limit when homing. It can run into a switch, back off, slow down and run into it slowly to increase the accuracy, and the back off a measured distance and set the home position. Even those cheap Radio Shack switches seem fairly accurate and repeatable.

Here is the changes to my xylotex_pinout.hal ini file (besides commenting out all the stuff that I did to link the 6 switches together as one big loop).

# create a signal for the x home
# create a signal for the x limit switches
newsig x-limit-reached bit
# connect it to the parport pin
linksp x-limit-reached parport.0.pin-11-in
linksp x-limit-reached axis.0.home-sw-in
linksp x-limit-reached axis.0.neg-lim-sw-in
linksp x-limit-reached axis.0.pos-lim-sw-in

# create a signal for the y home
# create a signal for the y limit switches
newsig y-limit-reached bit
# connect it to the parport pin
linksp y-limit-reached parport.0.pin-12-in
linksp y-limit-reached axis.1.home-sw-in
linksp y-limit-reached axis.1.neg-lim-sw-in
linksp y-limit-reached axis.1.pos-lim-sw-in

# create a signal for the z home
# create a signal for the z limit switches
newsig z-limit-reached bit
# connect it to the parport pin
linksp z-limit-reached parport.0.pin-13-in
linksp z-limit-reached axis.2.home-sw-in
linksp z-limit-reached axis.2.neg-lim-sw-in
linksp z-limit-reached axis.2.pos-lim-sw-in

If this helps anyone else then great!

Alan

[cyclestart]

Apologies for dragging up this old thread. I'm looking at the mini-io board and getting a bit confused.

Are you using the charge pump feature or is this easily bypassed? No obvious reference to it in this thread. Most of the info available seems to revolve around Mach software. Using xylotex (if that's a factor).