Replace rotary encoder with switches to control LCD in Marlin

Hi,

I'm trying to make a LCD panel to my Gen7 v1.5 running Marlin. Now I have basic LCD functionality in a 1602 display, adding some code to Configuration.h in Marlin:

//LCD and SD support
#define ULTRA_LCD  //general lcd support, also 16x2

//I2C PANELS

#define LCD_I2C_GENPANEL
#ifdef LCD_I2C_GENPANEL
  #define LCD_I2C_TYPE_PCF8575
  #define LCD_I2C_ADDRESS 0x20
  #define NEWPANEL
  //#define ULTIPANEL
#endif

There is no local source for a rotary encoder, so I'm thinking to replace this function with the minimun number of switches needed to do basic navigation, like: up, down, and activate buttons.

Is it possible? Can the up and down switches be attached to ATmega1284P pins directly or I need an IC (or whatever) as an interface like in the I2C LCD in order to adapt to Marlin code without add some new code? And what vars I need to add to `pins.h' to do this switches to work?

Thanks

same interest ... waiting the master to update