Number Input, Calculator Style

Using Arduino Programming Questions
1

Hey guys, first time post, frequent researcher for my project.

I've got a 4D Systems uLCD-43PT and an Arduino Due.
I have a custom keypad on it with 3 LED displays on it (0,1,2).

I'm surprised I'm having to ask this but I can't find it anywhere on the internet in the past several hours:

How do I take the numbers being typed in and put them in order in the LED display (just using #0 right now). I can get the numbers from the keys to the display, but how would I make it so that I could type in, say, 1,325?

Do i take each button press, put them into different variables, and then do the math to sort them into the right order? I've seen some calculators on touch screen displays but I never get any code to see how it works.

Thanks for any help guys.

2

This might help.

#include <Keypad.h>
#include <Wire.h> 
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x20,20,4);

long first = 0;
long second = 0;
long total = 0;
double Ftotal = 0;

char customKey;
const byte ROWS = 4;
const byte COLS = 4;

char keys[ROWS][COLS] = {
  {
    '1','2','3','+'}
  ,
  {
    '4','5','6','-'}
  ,
  {
    '7','8','9','*'}
  ,
  {
    'C','0','=','/'}
};
byte rowPins[ROWS] = {
  2,3,4,5}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {
  11,10,9,8}; //connect to the column pinouts of the keypad

//initialize an instance of class NewKeypad
Keypad customKeypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS); 

void setup(){
  lcd.init();                      // initialize the lcd 
  lcd.backlight();
}

void loop(){
  customKey = customKeypad.getKey();
  switch(customKey) 
  {
  case '0' ... '9': // This keeps collecting the first value until a operator is pressed "+-*/"
    lcd.setCursor(0,0);
    first = (first * 10) + (customKey - '0'); // This method is how you combine all the key presses into one value.
    // (customKey - '0') -> converts the keypad character to integer
    lcd.print(first);
    break;

  case '+':
    lcd.setCursor(0,1);
    lcd.print("+");
    second = SecondNumber(); // get the collected the second number
    total = first + second;
    lcd.setCursor(0,3);
    lcd.print(total);
    first = 0, second = 0; // reset values back to zero for next use
    break;

  case '-':
    lcd.setCursor(0,1);
    lcd.print("-");
    second = SecondNumber();
    total = first - second;
    lcd.setCursor(0,3);
    lcd.print(total);
    first = 0, second = 0;
    break;

  case '*':
    lcd.setCursor(0,1);
    lcd.print("*");
    second = SecondNumber();
    total = first * second;
    lcd.setCursor(0,3);
    lcd.print(total);
    first = 0, second = 0;
    break;

  case '/':
    lcd.setCursor(0,1);
    lcd.print("/");
    second = SecondNumber();
    lcd.setCursor(0,3);
    second == 0 ? 
      lcd.print("Invalid")
     :
      Ftotal = (float)first / (float)second;
    lcd.print(Ftotal);
    first = 0, second = 0;
    break;

  case 'C':
    lcd.clear();
    break;
  }
}

long SecondNumber(){
  while( 1 )
  {
    customKey = customKeypad.getKey();
    if(customKey >= '0' && customKey <= '9')
    {
      second = (second * 10) + (customKey - '0');
      lcd.setCursor(0,2);
      lcd.print(second);
    }

    if(customKey == '=') break;  //return second;
  }
 return second; 
}
3

modified and works beautifully. thanks!

4

Did you learn from it or just modify it?

5