Home + Limit from just 1 input pin: HAL config explained

Hey there, first post, still learning.

I have been configuring LinuxCNC 2.8 trying to understand what is happening so it wont bite me later...

When I set HOME+LIMITS on input pin 10 of parport, StepConf has put code like this in the HAL File:

I have edit to reflect my gantry y1 and y2 joints.
I now kind of understand what is happening in LUT5.

So far, I understand that:

1. LUT5 have 5 inputs and one output (IN4, IN3, IN2, IN1, IN0 and OUT) ;
2. IN4 receives the signal from the serial circuit of physical switches and is TRUE when the circuit is closed;
3. Homing operation doesn't depends upon LUT5 output, but Limit detection does;
4. IN3, IN2, IN1, IN0 are TRUE when joints 3,2,1,0 are homing, respectively;
5. LUT5 OUT is TRUE only when IN4 is FALSE and IN3, IN2, IN1, IN0 are TRUE
6. Only when LUT5 OUT is TRUE the joints limit switches input pins are TRUE (meaning a switch have been tripped)

My conclusion is that joint limit switches inputs are never TRUE because IN3, IN2, IN1, IN0 are never TRUE at the same time;

Where is my logic failing ?

Can someone explain the step-by-step events and states ocurring when a physical switch is tripped ?

Thanks guys,

Tried to edit the post and the forum editor is fighting me back, the harder I try, the worst it gets.

Click on the "source" in the upper left of the editor.
It will still mess up, but less.

Don't know if I can explain lut5 but here are some links that might help.
wiki.linuxcnc.org/cgi-bin/wiki.pl?Lut5
linuxcnc.org/docs/2.5/html/man/man9/lut5.9.html
linuxcnc.org/docs/2.8/html/hal/rtcomps.html#_lut5

trying to test it myself but running out of time this morning.

Hmm looks like setting the function to 0x1000000 is the output is never on.

JT

Hey John,

I understand LUT5.
if I have code like this:
I understand that LUT5 will only be TRUE when IN4=FALSE and IN3, IN2, IN1, IN0 are TRUE

Problem is what this logic represents in the wiring of HAL from the first post, it does not make sense to me.

I just tested that with the axis sim and out is never on... gotta run to work now.

JT

I understand that LUT5 will only be TRUE when IN4=FALSE and IN3, IN2, IN1, IN0 are TRUE

setp lut5.0.function 0x8000

This is the function for the above.
 
JT

hum... maybe I've got LUT5 logic wrong.
I was expecting function 0x10000 to be:

but your debug shows LUT5 function to be 0x8000 for that situation.
in fact the difference between both in binary is this:

Could you explain how did you wired sim.axis to simulate this LUT5 output ?
I'm still learning HAL and could not reproduce your screen

Actually setp lut5.0.function 0x10000 is:
 
 

JT

I have done this comparison of HAL wiring in sim.axis homing and lut5 homing+limits:
 
but don't know how to translate to simulated env.