Arduino Taster über Widerstände

Hallo,
Habe ein SainSmart Display 1602 wie lese ich da am besten die Taster aus
oder wie kann ich das beispiel Projekt umschreiben damit nachdem die 
Taster ausgelesen wurden das eigentliche programm kommen kann.






/*
  The circuit:
 * LCD RS pin to digital pin 8
 * LCD Enable pin to digital pin 9
 * LCD D4 pin to digital pin 4
 * LCD D5 pin to digital pin 5
 * LCD D6 pin to digital pin 6
 * LCD D7 pin to digital pin 7
 * LCD BL pin to digital pin 10
 * KEY pin to analogl pin 0
 */

#include <LiquidCrystal.h>
#include <Keys.h>
LiquidCrystal lcd(8, 13, 9, 4, 5, 6, 7);

char msgs[5][16] = {"Right Key OK ",
                    "Up Key OK    ",
                    "Down Key OK  ",
                    "Left Key OK  ",
                    "Select Key OK" };

int adc_key_val[5] ={50, 200, 400, 600, 800 };
int NUM_KEYS = 5;
int adc_key_in;
int key=-1;
int oldkey=-1;
void setup()

{
  lcd.clear();
  lcd.begin(16, 2);
  lcd.setCursor(0,0);
  lcd.print("ADC key testing");
  Serial.begin(9600);
}

void loop()
{
  adc_key_in = analogRead(0);    // read the value from the sensor
  key = get_key(adc_key_in);  // convert into key press

  if (key != oldkey)   // if keypress is detected
   {
    delay(50);  // wait for debounce time
    adc_key_in = analogRead(0);    // read the value from the sensor
    key = get_key(adc_key_in);    // convert into key press
    if (key != oldkey)
    {
      lcd.setCursor(0, 1);
      oldkey = key;
      if (key >=0){
       int Button=key;
           Serial.print(Button);
      }
    }
  }
 delay(100);
}


 // Convert ADC value to key number
int get_key(unsigned int input)
{
    int k;

    for (k = 0; k < NUM_KEYS; k++)
    {
      if (input < adc_key_val[k])
 {
            return k;
        }
   }

    if (k >= NUM_KEYS)k = -1;  // No valid key pressed

 return k;