Embedded Systems

/* Simple calculator

Circuit Connections:
**LCD
               Ground                    => Gnd
               Power                     => Vcc
               Contrast                  => Potentiometer
               RS                        => PIN_A5
               RW                        => Gnd
               E                         => PIN_A4
               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
**Potentiometer1
               Terminal 1                => Gnd
               Wiper                     => LCD_Contrast
               Terminal 2                => Vcc
**Keypad
               PIN_5 => Column4
               PIN_6 => Column3
               PIN_7 => Column2
               PIN_8 => Column1
               PIN_9 => Row4
               PIN_10 => Row3
               PIN_11 => Row2
               PIN_12 => Row1
*/
//include the library
#include <LiquidCrystal.h>
#define RS A5         //give the name "RS" to PIN_A5
#define EN A4         //give the name "EN" to PIN_A4
#define DB4 0         //give the name "DB4" to PIN_0
#define DB5 1         //give the name "DB5" to PIN_1
#define DB6 2         //give the name "DB6" to PIN_2
#define DB7 3         //give the name "DB7" to PIN_3

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

//inlcude the library
#include <Keypad.h>
const byte cols = 4; //four columns
const byte rows = 4; //four rows
//keypad output
char keys[rows][cols] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};

//configure the Arduino Uno - Keypad interface
byte row_pins[] = {12,11,10,9}; //pins connect to the rows
byte col_pins[] = {8, 7, 6, 5}; //pins connect to the columns
Keypad keypad = Keypad(makeKeymap(keys), row_pins, col_pins, rows, cols);

//variable to save keypad's charachters
char key;
//variable for the first number
int num1;
//variable for the second number
int num2;
//variable for the operation
char operation;
//variable for the result
float result;

//The setup() function initializes and sets the initial values
//It will only run once after each power up or reset
void setup(){
//configure the LCD's columns and rows
lcd.begin(16, 2);
}

//loops consecutively
void loop(){
//the first number
do{
   //wait until a key is pressed
   key=keypad.waitForKey();
   //call the "convert_to_number"
   num1=convert_to_number(key);
   }
while(num1>9);
//print the first number
lcd.print(num1);
//wait 0.2s
delay(200);

//the operation
do{
   //wait until a key is pressed
   operation=keypad.waitForKey();
   }
while(operation!='A' && operation!='B' && operation!='C' && operation!='D');
//print the operation
if(operation=='A'){
   lcd.print(" + ");
   }
else if(operation=='B'){
   lcd.print(" - ");
   }
else if(operation=='C'){
   lcd.print(" * ");
   }
else if(operation=='D'){
   lcd.print(" / ");
   }
//wait 0.2s
delay(200);

//the second number
do{
   //wait until a key is pressed
   key=keypad.waitForKey();
   //call the "convert_to_number"
   num2=convert_to_number(key);
   }
while(num2>9);
//print the second number
lcd.print(num2);
//wait 0.2s
delay(200);

//calculate
if(operation=='A'){
   result=num1+num2;
   }
else if(operation=='B'){
   result=num1-num2;
   }
else if(operation=='C'){
   result=num1*num2;
   }
else if(operation=='D'){
   result=float(num1)/num2;
   }
//print the result
lcd.print(" = ");
lcd.print(result);

//wait until the "#" is pressed
do{
   key=keypad.waitForKey();
   }
while(key!='#');
//clear the LCD
lcd.clear();
}

//this function converts 
//keypad's character to integer
int convert_to_number(char c){
if(c=='0'){
   return 0;
   }
else if(c=='1'){
   return 1;
   }
else if(c=='2'){
   return 2;
   }
else if(c=='3'){
   return 3;
   }
else if(c=='4'){
   return 4;
   }
else if(c=='5'){
   return 5;
   }
else if(c=='6'){
   return 6;
   }
else if(c=='7'){
   return 7;
   }
else if(c=='8'){
   return 8;
   }
else if(c=='9'){
   return 9;
   }
else if(c=='A'){
   return 10;
   }
else if(c=='B'){
   return 11;
   }
else if(c=='C'){
   return 12;
   }
else if(c=='D'){
   return 13;
   }
else if(c=='*'){
   return 14;
   }
else {// if(c=='#'){
   return 15;
   }
}