Using LCD with Arduino

gistfile1.ino

/*
  Show analog input value using a LCD.
  Turn on and off the backlight with a button.
  
  By Antonio Perez <aperez@skarcha.com>
  
  Public Domain
 */

// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

const int analogInPin = A0;
const int lightPin = 10;
const int buttonPin = 9;

int sensorValue = 0;
int buttonState = 0;
int lastButtonState = 0;
int powerLight = LOW;

void setup() {
  pinMode(lightPin, OUTPUT);
  pinMode(buttonPin, INPUT);

  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);
  // Print a message to the LCD.
  lcd.print("Resistor value:");
}

void loop() {
  sensorValue = analogRead (analogInPin);
  buttonState = digitalRead (buttonPin);

  if (buttonState != lastButtonState) {
    if (buttonState == HIGH) {
      powerLight = !powerLight;
      digitalWrite (lightPin, powerLight);
    }  
    lastButtonState = buttonState;
  }

  // set the cursor to column 0, line 1
  // (note: line 1 is the second row, since counting begins with 0):
  lcd.setCursor(0, 1);
  // print the number of seconds since reset:
  lcd.print(sensorValue);
}