marlin add encoder or push buttons

let's say I want to add an encoder, a i2c lcd and an sd card reader.
but let's say if you don't have an encoder handy, why can't we use three buttons one pulls pin X1 high (UP), the second button pulls X2 high(down), and the third button pulls both X1 and X2 high,(select)(If you wanted to be even cheaper pushing both up and down would be select) therefore only using 2 pins and able to select the same way. just curious how I would set up in this way, let's say with a repeat rate of 0.5 seconds in code, also how do I setup an i2c lcd?
also how do I define the 4th pin I know I have to use miso, etc but the 4th's is user definable if I understand correctly.
Please I am a coding noob need some help, and would the button thing work?
terramir

Edited 1 time(s). Last edit at 02/14/2015 02:49PM by terramir.

Hi,

the way i see it, it is possible, but not without diving deep into the Firmwares code.
The other way would be to use a second arduino, and emulate the behavior of an encoder that way,
but this would make it bulky and the costs are higher in comparison.

There are Displays out there with a comon i2c interface. Pin wise i would go in that direction, but i have no idea
if Marlin supports it out of the box. Never tried to hoock up stuff like this so far.