increment and decrement array value using keypad and LCD

Projects Programming
1

Hello Everyone. I wanted to do programming to enter two digit number through keypad and display it on LCD. Also I want to program key 'A' as if it is entered, next number to that key should display on LCD .For example, if I enter 21 number through keypad so when I press key 'A', next number i,e 22 should be displayed on LCD..but i couldnt get ouput for program i have written'...excuse me if I asked any silly question...here is my code:

#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins

LiquidCrystal lcd(8, 9, 10, 11, 12, 13);//RS,EN,D4,D5,D6,D7

#include <Keypad.h>//header for keypad commands enabling

const byte ROWS = 4; // Four rows
int i=0;

const byte COLS = 4; // Three colum
int my_key [50]= {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,
                            17,18,19,20,21,22,23,24,25,26,27,28,29,
                            30,31,32,33,34,35,36,37,38,39,40,41,
                             42,43,44,45,46,47,48,49,50};

// Define the Keymap

char keys[ROWS][COLS] = {

  {'1','2','3','A'},

  {'4','5','6','B'},

  {'7','8','9','C'},

  {'#','0','*','D'}

};

// Connect keypad ROW0, ROW1, ROW2 and ROW3 to these Arduino pins.

byte rowPins[ROWS] = { 0, 1, 2, 3 };

// Connect keypad COL0, COL1 and COL2 to these Arduino pins.

byte colPins[COLS] = { 4, 5, 6, 7 };

//  Create the Keypad

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

void setup()

{

  for(int k=8;k<14;k++)

  {

    pinMode(k,OUTPUT);//pins 8-14 are enabled as output

  }

  lcd.begin(16, 2);//initializing LCD
 
  lcd.print(my_key[i]) ;
  
  int key_event();
   
}



void loop()

{

}

 int key_event()
 {
  
  char key = kpd.getKey();
 if (key != NO_KEY)
 {
 i=1; 

if (key == 'A' )
   {
    i=i+1;
    lcd.setCursor(0, 1);
    lcd.print(my_key[i]) ;
   }
else if(key== 'B')
   {
   i=i-1;
  lcd.setCursor(3, 1);
  lcd.print(my_key[i-1]);
   }
 }              
}
2

Why does

your code

have so much

white space?

Get rid of most of the blank lines.

int my_key [50]= {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,
                            17,18,19,20,21,22,23,24,25,26,27,28,29,
                            30,31,32,33,34,35,36,37,38,39,40,41,
                             42,43,44,45,46,47,48,49,50};

An array where every value in the array is 1 more than the index value is pointless.

  int key_event();

Why is there a function prototype in setup()? An incorrect function prototype, at that.

The setup() function is not telling the Keypad instance to call a function when a key is pressed, and loop() doesn't read the keypad, so you might as well not have connected it.

3

thank so much for replying..apologise for inconvenience...i have improved my program stii not getting right output..kindly help me with code.
my code:

#include <LiquidCrystal.h>

#include <Key.h>
#include <Keypad.h>
LiquidCrystal lcd(8, 9, 10, 11, 12, 13);
const byte ROWS = 4;
const byte COLS = 4;

char keys[ROWS][COLS] = {

  {'1','2','3','A'},

  {'4','5','6','B'},

  {'7','8','9','C'},

  {'*','0','#','D'}
};
byte rowPins[ROWS] = { 0,1,2,3 };
byte colPins[COLS] = { 4,5,6,7 };
Keypad kpd = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );
int v1 = 0;
int v2 = 0;
void setup() {
lcd.begin(16, 2);
}
void loop() {  
   v1 = GetNumber();
   v2 = GetNumber();
}
int GetNumber()
{  
  int num = 0;
  char key = kpd.getKey();
   while(key != NO_KEY)
  {
   while(key != '#')
   {
      switch (key)
      {
         case NO_KEY:
            break;
            case '0': case '1': case '2': case '3': case '4':
            case '5': case '6': case '7': case '8': case '9':
            lcd.print(key);
            num = num * 10 + (key - '0');
            num = num + key;
            break;
            case '*':
            num = 0;
            lcd.clear();
            break;
            case 'A': 
            num = ++num;
            lcd.print(num);
            break;
       }
      key = kpd.getKey();      
   }
   return num;
  } 
}
 :)
4

stii not getting right output.

What do you get ?

num = num + key;

Why ?

What do you see if you print the intermediate values to the serial monitor in the GetNumber() function ?

5

when I press key 1 and A..I got output as 51 and for key 2 and A..I got output as 563

6 
          num = num * 10 + (key - '0');
          num = num + key;

Work through with pencil and paper what the value of num will be when you press '1' starting with num = 0. Print num after the first line if it helps

You did not answer my question as to why the second line is there.

7

The extra blank lines are a copy/paste artifact with line-endings, not in the original code I suspect!