Using high impedance limit switches

[LewisB]

In order to get a micron-scale accuracy I'm using a precision tool sensor touch switch that has an internal resistance of around 3MOhms and a maximum internal current of 10mA. I think the duet is unable to tell the difference between open and closed switch as I can get the stop to trigger using a wire (just touching the sensor nodes to close the loop) but the switch itself doesn't affect the print. If there a value in the firmware for sensor sensitivity?

[dc42]

The devices connected to the endstop inputs need to sink about 1mA of current with a voltage drop no greater than about 1V.