A Axis Limit Switch Not Detected in UCCNC — Dual Y/Gantry Au

[TheG]

Hi all,

I’m setting up auto-squaring for a dual Y-axis gantry using UCCNC and an AXBB-E controller. A is slaved to Y, and both sides of the gantry have inductive proximity sensors (Huchoo SN04-N) installed for homing.

The issue:
• Both limit switches function and light up when triggered.
• I’ve swapped them around, and they both work fine on the Y axis.
• But when wired to the A axis limit input (Port 2, Pin 3), UCCNC doesn’t register the signal — no response in the I/O monitor.
• I’ve verified the port and pin settings, and “Active low” is enabled.
• The input pin is definitely working — I tested it with the Y switch and confirmed it triggers correctly in UCCNC.

I managed to get both sides to move using a workaround: I set the A axis to home and made it retract when the Y switch is triggered — but that causes misalignment and defeats the point of auto-squaring.

What I need is proper dual-axis homing (Y and A homing independently) so that the gantry squares itself, then A can be re-slaved to Y.

Anyone know why UCCNC isn’t seeing the A axis limit switch input, or how to configure dual homing for Y/A properly?

Thanks a lot in advance!

[cncdrive]

You just have to set the home inputs as per your connection and if it is a master/slave axes pair then it will automatically square the gantry.

[TheG]

Thanks for the reply!

I understand UCCNC should automatically handle gantry squaring if both Y and A have home switches set correctly. The problem is: UCCNC does not detect the A axis home switch at all, even though:
• I’ve confirmed this pin works by testing with the Y switch.
• The limit switch (Huchoo SN04-N) is functional — LED lights up and gives proper signal (tested with multimeter and when switching to another port).
• The input is set to “Active Low,” like the Y switch.
• Yet in the I/O monitor, triggering the A limit switch shows no change, while the same switch shows input when used for Y.

So while I’d love to let UCCNC handle squaring, I can’t even get both inputs recognized at the same time. Could there be a bug, config issue, or limitation with AXBB-E input mapping? I've tried every possible setting of the pins..

[cncdrive]

UCCNC handles gantry squaring as I described.
Can you try a different input please?
And how did you determinate that squaring is not happening?

[TheG]

Thanks
yes, I’ve tested multiple inputs.

I un-slaved Y and A for testing and set both axes to home separately. Y triggers and homes fine. A keeps going until it crashes, because its switch isn’t detected — that’s how I noticed it’s not squaring or stopping. I even tried making A retract when Y is triggered, but that causes misalignment.

So right now I’m stuck because UCCNC doesn’t seem to see the A limit switch at all, even though I know the hardware and pin work.

[ger21]

I'm a little confused. Are you saying that port 2 pin 3 does not work with any switch?
You have both home switches set to that pin.
Have you tried some other type of switch on that pin?

For homing to work, the two home switches need to be on different pins.