Adding Backspace in Keypad

Using Arduino Programming Questions
1

Hi, I'm making an ATM in which we have to enter our **BMI(Body Mass Index)**and I am having some difficulties in working with keypad see I have programmed the Arduino in the way that I can Enter my BMI and I will be give money as BMI * 10 but I want to add backspace when I click the # Key. So can anyone help me with this problem
This is My Code

#include <Keypad.h>

const byte ROWS = 4; //four rows
const byte COLS = 4; //four columns
char keys[ROWS][COLS] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};

byte rowPins[ROWS] = {2, 3, 4, 5}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {A0, A1, A2, A3}; //connect to the column pinouts of the keypad

Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

float enteredBMI = 0.0; // Variable to store entered BMI
float totalMoney = 0.0; // Variable to store total money

void setup() {
  Serial.begin(9600);
}

void loop() {
  char key = keypad.getKey();

  if (key) {
    if (key == 'A') {
      // The user pressed "A," calculate total money and display it
      totalMoney = enteredBMI * 10.0;
      Serial.print("Total Money: $");
      Serial.println(totalMoney);
      enteredBMI = 0.0; // Clear the entered BMI
    } else {
      Serial.print(key); // Print the entered key
      enteredBMI = enteredBMI * 10.0 + (key - '0'); // Append key to enteredBMI
    }
  }
}
2

The first thing to do is to change the else clause so that the total is only updated if a numeric key is pressed

Come back when you have done that

3

No, see I want the total to be submitted when I click the "A" key. So Else clause is necessary

4

The else clause is necessary but is currently wrong

What happens to the total if you press the 'A' key, for instance ?

5

The number will be multiplied by 10 when we press "A"

6

But what if you press the 'B' key ?

7 
#include <Keypad.h>

const byte ROWS = 4; //four rows
const byte COLS = 4; //four columns
const char keys[ROWS][COLS] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};

const byte rowPins[ROWS] = {2, 3, 4, 5}; //connect to the row pinouts of the keypad
const byte colPins[COLS] = {A0, A1, A2, A3}; //connect to the column pinouts of the keypad

Keypad keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

int enteredBMI = 0; // Variable to store entered BMI
//int totalMoney = 0; // Variable to store total money

void setup() {
  Serial.begin(9600);
}

void loop() {
  char key = keypad.getKey();

  if (key != NO_KEY) {
    Serial.print(key); // Print the entered key
    if (key >= '0' && key <= '9') enteredBMI = enteredBMI * 10 + key - '0';
    if (key == '#') enteredBMI = enteredBMI / 10 ;
    if (key == 'A') {
      // The user pressed "A," calculate total money and display it
      //totalMoney = enteredBMI * 10;
      Serial.print("Total Money: $");
      Serial.println(enteredBMI);
      enteredBMI = 0; // Clear the entered BMI
    }
  }
}
1 Like
8

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.