Embedded Systems

/* LCD display() / noDisplay()
Circuit Connections:
** LCD
               Ground                    => Gnd
               Power                     => Vcc
               Contrast                  => Potentiometer
               RS                        => PIN_0
               RW                        => Gnd
               E                         => PIN_1
               DB0                       => Gnd
               DB1                       => Gnd
               DB2                       => Gnd
               DB3                       => Gnd
               DB4                       => PIN_2
               DB5                       => PIN_3
               DB6                       => PIN_4
               DB7                       => PIN_5
               LED Anode                 => Vcc
               LED Cathode               => Resistor 220Ω => Gnd
** Potentiometer
               Terminal 1                => Gnd
               Wiper                     => LCD_Contrast
               Terminal 2                => Vcc
** PIN_8 (built-in pullup)               => Push-button1  => Gnd
** PIN_9 (built-in pullup)               => Push-button2  => Gnd
*/
//include the library
#include <LiquidCrystal.h>
#define RS 0              //give the name "RS" to PIN_0
#define EN 1              //give the name "EN" to PIN_1
#define DB4 2             //give the name "DB4" to PIN_2
#define DB5 3             //give the name "DB5" to PIN_3
#define DB6 4             //give the name "DB6" to PIN_4
#define DB7 5             //give the name "DB7" to PIN_5
#define pb1 8             //give the name "pb1" to PIN_8
#define pb2 9             //give the name "pb1" to PIN_9

//configure the library with Arduino Uno - LCD interface
LiquidCrystal lcd(RS, EN, DB4, DB5, DB6, DB7);

//The setup() function initializes and sets the initial values
//It will only run once after each powerup or reset
void setup() {
//Configure the PIN_8 to behave as input with pull-up resistor
pinMode(pb1, INPUT_PULLUP);  
//Configure the PIN_9 to behave as input with pull-up resistor 
pinMode(pb2, INPUT_PULLUP);  
//configure the LCD's columns and rows
lcd.begin(16, 2);
//print a message
lcd.print("can you see me?");
}

//This function loops consecutively
void loop() {
//check the push-button1
if(digitalRead(pb1)==false){             //pb1 is pressed
   delay(25);                            //wait for debouncing
   while(digitalRead(pb1)==false){;}     //until pb1 is released
   lcd.noDisplay();                      //the text is disappeared
   }
//check the push-button2
if(digitalRead(pb2)==false){              //pb2 is pressed
   delay(25);                             //wait for debouncing
   while(digitalRead(pb2)==false){;}      //until pb2 is released 
   lcd.display();                         //the text is appeared
   }
}