[otherguy]

how is your limit switch wired?

The digital sidecar has internal pullup resistors on its input channels. This means that when nothing is connected to the pins it sees 5v.

Your switch should have a ground and a signal wire connected to it (5v isnt' required). Per your stated wiring, when the switch is pressed, the signal wire should be shorted to ground. If this is not the case, then you won't see a logic level state change at the digital side car.