Delta printer on M4 motherboard

Is it possible to setup a M4 board for a delta printer? I looked at the pin map in the git and see end stops for X. Y and Z but did not see a pin for the bltouch.

#define X_MIN_PIN

#define Y_MIN_PIN

#define Z_MIN_PIN

But for a Delta I need something like

#define X_MAX_PIN 4

#define Y_MAX_PIN 35

#define Z_MAX_PIN 21

#define Z_MIN_PIN ??? //touch sensor for leveling