Analog vs Digital PIN assignment (no replies)

Hello,

How are the pins declared analog or digital?

To keep things short and simple I will say what I am doing, and that it is working. My problem is I do not understand how it is working.

Basically I have a toggle switch connected to the X-Min Endstop pin on a RAMPS1.4 board, the pin is assigned as follows:

#define TOGGLE_SWITCH  3

Then I have a filament width sensor connected to AUX_1 peripheral, with the pin assigned as follows:

// Use the RAMPS 1.4 Analog input 3 on the AUX_1 connector
#define FILWIDTH_PIN        3 // ANALOG NUMBERING

(Note that the default is normally pin 5 on AUX_2, for my configuration I switched it to pin 3 on AUX_1.)

I have set up some basic code to change the output based on the state of the toggle switch, and when I run the FW the output of the filament width sensor is correct. Then, when I toggle the switch, the output is displayed accordingly and correctly. Which means the two pins, and their assignment, are not interfering with each other. I do not understand why not?

I know the sensor pin must be analog (input), its digital counterpart is 57 (A3 or D57), and the digital pin, well that conforms to the default configuration.

I am using this png file for the PIN verification. Please offer me any insight into this, I have been on the marlin site and github, but have found no clear indication on this distinction (between analog and digital).

Thank you.