Need help with backspacing with a 3x4 keypad

Projects Programming
1

Hello,

Im currently working on a project to control a steppermotor(23) with a lcd and a 3x4 keypad.

The problem im getting is that my backspace is not working properly.

The code is not finished yet but im testing it every step i take. Currently my code is looking like this and there is a error between the lines: 137 -> 164 (void deletenumber)

#include <Keypad.h>
#include <Wire.h> 
#include <LiquidCrystal_I2C.h>
//////////////////////////////////////////////////////////////////////
LiquidCrystal_I2C lcd(0x27, 20, 4);
const int stepPin = 5; 
const int dirPin = 2; 
const int enPin = 8;
volatile int firstnumber=99;  // used to tell how many numbers were entered on keypad
volatile int secondnumber=99;
volatile int thirdnumber=99;
volatile int fourthnumber=99;
  
/////////////////////////////////////////////////////////////////////
const byte ROWS = 4; // Vier rijen
const byte COLS = 3; // 3 kollomen
char keys[ROWS][COLS] = {
  {'1','2','3'},
  {'4','5','6'},
  {'7','8','9'},
  {'*','0','#'}
};
byte rowPins[ROWS] = {28, 26, 24, 22}; // Arduino pins naar de 4 rijen
byte colPins[COLS] = {35, 33, 31}; // Arduino pins naar de 3 kollomen
Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );  // Keypad Library definition

////////////////////////////////////////////////////////////////////// 

void setup() {
  lcd.init();                   // initialiseer het LCD scherm
  lcd.backlight();              // zet de backlight aan

  lcd.clear();                  // wis het scherm
  lcd.setCursor(0, 0);          // zet de cursor op positie 1, regel 1
  lcd.print("Huidige  maat|");    // schrijf op scherm
  lcd.setCursor(0, 1);
  lcd.print("-------------+------");   
  lcd.setCursor(0, 2);          
  lcd.print("Gewenste maat|");
  lcd.setCursor(0, 3);
  lcd.print("--------------------");   
  lcd.setCursor(18, 0);         
  lcd.print("MM");              
  lcd.setCursor(18, 2);         
  lcd.print("MM");              

//////////////////////////////////////////////////////////////////////

  pinMode(stepPin,OUTPUT); 
  pinMode(dirPin,OUTPUT);
  pinMode(enPin,OUTPUT);
  digitalWrite(enPin,LOW);
}
 
void loop() {
   char keypressed = keypad.getKey();  // Get value of keypad button if pressed
  if (keypressed != NO_KEY){  // If keypad button pressed check which key it was
    switch (keypressed) {
      
      case '1':
        checknumber(1);
      break;
        
      case '2':
        checknumber(2);
      break;

      case '3':
        checknumber(3);
      break;

      case '4':
        checknumber(4);
      break;

      case '5':
        checknumber(5);
      break;

      case '6':
        checknumber(6);
      break;

      case '7':
        checknumber(7);
      break;

      case '8':
        checknumber(8);
      break;

      case '9':
        checknumber(9);
      break;

      case '0':
        checknumber(0);
      break;

      case '*':
        deletenumber();
      break;

    }
  }
} 
void checknumber(int x){
  if (firstnumber == 99) { // Check if this is the first number entered
    firstnumber=x;
    String displayvalue = String(firstnumber);  //  Transform int to a string for display
      lcd.setCursor(14, 2);         
      lcd.print(displayvalue);
    
  } else {
    if (secondnumber == 99) {  // Check if it's the 2nd number entered
      secondnumber=x;
      String displayvalue = (String(firstnumber) + String(secondnumber));
      lcd.setCursor(14, 2);         
      lcd.print(displayvalue);
      
    } else {  // Check if the 3rd number entered
      if (thirdnumber == 99) {
         thirdnumber=x;  
         String displayvalue = (String(firstnumber) + String(secondnumber) + String(thirdnumber));
         lcd.setCursor(14, 2);         
         lcd.print(displayvalue);
     } else {  // It must be the 4rd number entered
      fourthnumber=x;
      String displayvalue = (String(firstnumber) + String(secondnumber) + String(thirdnumber) + String(fourthnumber));
         lcd.setCursor(14, 2);         
         lcd.print(displayvalue);
      }
    }
  }
}

void deletenumber() {  // Used to backspace entered numbers
 if (fourthnumber !=99) {
     String displayvalue = (String(firstnumber) + String(secondnumber) + String(thirdnumber));
     lcd.setCursor (14, 2);
     lcd.print(displayvalue);
     fourthnumber=99;
  }
  else
   if (thirdnumber !=99) {
       String displayvalue = (String(firstnumber) + String(secondnumber));
        lcd.setCursor(14, 2);         
        lcd.print(displayvalue);
        thirdnumber=99;
   } 
   else {
     if (secondnumber !=99) {
       String displayvalue = String(firstnumber);
       lcd.setCursor(14, 2);
       lcd.print(displayvalue);
       secondnumber=99;
    } 
    else {
      if (firstnumber !=99) {
        String displayvalue = " ";
        lcd.setCursor(14, 2);
        lcd.print(displayvalue);
        firstnumber=99;
       } 
    }
  }
}
2

You should describe in detail what behaviour of the code you observe and what behaviour you want to have

best regards Stefan

3

allright what i want to achieve is this:

I want to enter 2650 in my keypad. But i accidently pressed the wrong button so now my lcd says 2655 for example. So i want to backspace the last digit using the (.) on the keypad. but it doesnt it doesnt work. it only works when i want to backspace the first digit.
for example:
I press 1 on the keypad. i press (.) after. now the 1 removes like its supossed to but when ever i press 11 for example and i try to backspace it won't work. when i press backspace again it wil remove the first digit but the second digit stays at the same place.

Do you know how to solve this?

Thanks for your time

4

still not precise enough
You enter a single digit and backspace works
I don't understand which key this strange () is

char keys[ROWS][COLS] = {
  {'1','2','3'}, // which key is it?
  {'4','5','6'},
  {'7','8','9'},
  {'*','0','#'}
};

if you entered two digits like "11" and you press backspace what do you observe on the display?

best regards Stefan

5

The key im trying to type wont show up in the commands its the star symbol (bottom left of the char keys)

if i enter 11 it will show [11 ]
when i press backspace it will show [11 ]
when i press back space again it will show [ 1 ]
its hard to explain like this but it removes the first digit and leaves the second one where it is

6

if i enter 37 it will show [37 ]
when i press backspace it will show [37 ]
when i press back space again it will show [ 7 ]

it becomes more precise by using two different digits like 37
is this correct? The second digit the 7 stays there
and if you press backspace again and again the "7" stays there forever?

The basic idea of your code is: you initialise four variables with 99 to indicate the digits are not yet typed in on the keyboard
then you press a digit on the keyboard and check if the corresponding variable has value 99
if it has value 99 you assign the pressed digit

Me personal I would use this approach:
if you want to enter 4-digits numbers like 1234, 2560, etc. there is one single array of char with 5 elements. You need 5 elements because a char-array must always be terminated with value 0 for indicating end-of-string

Arrays start at index 0. This means a 5-element array has the index-numbers

myCharArray[0]
myCharArray[1]
myCharArray[2]
myCharArray[3]
myCharArray[4]

each time you press a digit on your keyboard the digit is assigned to an array-element
and the index-number is increased by one

first press is a "5"
myCharArray[0] = '5';
and additionally to terminate the string
myCharArray[1] = 0;

second press is a "6"
myCharArray[1] = '6';
and additionally to terminate the string
myCharArray[2] = 0;

third press is a "8"
myCharArray[2] = '8';
and additionally to terminate the string
myCharArray[3] = 0;

fourth press is a "9"
myCharArray[3] = '9';
and additionally to terminate the string
myCharArray[4] = 0;

and on the display you simple print

lcd.print(myCharArray);

if you use backspace
the last entered digit gets assigned 0
example
you entered three digits

568
corresponding to
myCharArray[0] contains a 5
myCharArray[1] contains a 6
myCharArray[2] contains a 8

last valid digit has index-number 2

you press backspace one time
and you execute

myCharArray[2] = 0;

and you are done because the zero indicate end-of-string
For later use you convert the array-of char to an integer with function
atoi()
which also uses the terminating zero for finding the digits

best regards Stefan

7

i think this is simpler

#undef MyHW
#ifdef MyHW
# include "sim.hh"
#else
# include <Keypad.h>
# include <Wire.h>
# include <LiquidCrystal_I2C.h>
#endif

//////////////////////////////////////////////////////////////////////
LiquidCrystal_I2C lcd (0x27, 20, 4);
const int stepPin = 5;
const int dirPin = 2;
const int enPin = 8;

unsigned long number;

/////////////////////////////////////////////////////////////////////
const byte ROWS = 4; // Vier rijen
const byte COLS = 3; // 3 kollomen
char keys[ROWS][COLS] = {
    {'1','2','3'},
    {'4','5','6'},
    {'7','8','9'},
    {'*','0','#'}
};

byte rowPins[ROWS] = {28, 26, 24, 22}; // Arduino pins naar de 4 rijen
byte colPins[COLS] = {35, 33, 31}; // Arduino pins naar de 3 kollomen
Keypad keypad = Keypad ( makeKeymap (keys), rowPins, colPins, ROWS, COLS );  // Keypad Library definition

//////////////////////////////////////////////////////////////////////

void setup () {
    lcd.init ();                   // initialiseer het LCD scherm
    lcd.backlight ();              // zet de backlight aan

    lcd.clear ();                  // wis het scherm
    lcd.setCursor (0, 0);          // zet de cursor op positie 1, regel 1
    lcd.print ("Huidige  maat|");    // schrijf op scherm
    lcd.setCursor (0, 1);
    lcd.print ("-------------+------");
    lcd.setCursor (0, 2);
    lcd.print ("Gewenste maat|");
    lcd.setCursor (0, 3);
    lcd.print ("--------------------");
    lcd.setCursor (18, 0);
    lcd.print ("MM");
    lcd.setCursor (18, 2);
    lcd.print ("MM");

    //////////////////////////////////////////////////////////////////////

    pinMode (stepPin,OUTPUT);
    pinMode (dirPin,OUTPUT);
    pinMode (enPin,OUTPUT);
    digitalWrite (enPin,LOW);
}


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

    switch (key) {
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
    case '0':
        number = (10*number) % 1000 + key-'0';
        lcd.setCursor (14, 2);
        lcd.print (number);
        break;

    case '*':
        number /= 10;
        lcd.setCursor (14, 2);
        lcd.print (number);
        break;

    case NO_KEY:
        break;
    }
}