Using a 4*4 keypad to enter an integer value

Question

I have a 4*4 keypad and I want to use it to enter a number. I will then use this number as a delay to a LED or a motor to run for the specified time. This is my sample code:

#include<Keypad.h>
#include<LiquidCrystal.h>
const byte numRows = 4; //number of rows on keypad
const byte numCols = 4; //number of columns on keypad


char keymap[numRows][numCols]= 
{
{'1', '2', '3', 'A'}, 
{'4', '5', '6', 'B'}, 
{'7', '8', '9', 'C'},
{'X', '0', 'Y', 'D'}
};

char value[4]="";
int index = 0;

byte rowPins[numRows] = {22,23,24,25}; //Rows 0 to 3
byte colPins[numCols]= {26,27,28,29}; //Columns 0 to 3

Keypad key= Keypad(makeKeymap(keymap), rowPins, colPins, numRows,numCols);

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {
Serial.begin(9600);
pinMode(13,OUTPUT);
lcd.begin(20,4);

lcd.print("       WELCOME      ");
delay(100);
}

void loop() {
char keypress = key.getKey();
while (keypress != NO_KEY){  
  if (keypress == 'X'){
      lcd.clear();
      for(int j=0;j<=4;j++){
        value[j]=0;
      }
      index=0;
      }
   else if (keypress == 'Y'){
      int amt = atoi(value);
      digitalWrite(13, HIGH);
      delay(amt);
      } 
   else   
      value[index]=keypress;
      index++;
    }  
}

How do I read the value returned by the keypad as an integer? (When I press 3 I want to read 3 not "3").

from this code i should be able to get the input from the keypad and pass the value to delay the led — DANIEL NTIM-ADU SAITO
– DANIEL NTIM-ADU SAITO, Commented May 3, 2017 at 20:15
Am I missing something, any reason you can't initialize keymap to contain 3 rather than '3'? It's an array of 8 bit values, why not set it to be the numbers you want rather than text characters? — Andrew
– Andrew, Commented May 4, 2017 at 15:51

sa_leinad · Accepted Answer · 2018-01-01 11:56:54Z

2

You can easily read by this line of code

value = anyDigitFromKeypad - 48

e.g value = "3"-48 = 3

edited Jan 1, 2018 at 11:56

sa_leinad

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answered Jan 1, 2018 at 10:52

Furqan

212 bronze badges

1

I would write '0' rather than 48. The two are equivalent, but the former makes it clearer that you are subtracting the code point of the digit zero.

Edgar Bonet
– Edgar Bonet

2018-01-01 16:35:38 +00:00
Commented Jan 1, 2018 at 16:35

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Majenko · Accepted Answer · 2017-05-04 15:49:54Z

1

Your problem is that you have your keypress matching inside a while loop. That means it will, once matched once, continue matching over and over again as infinitum. You need to replace your while with an if so it only runs once for each keypress.

answered May 4, 2017 at 15:49

Majenko

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