Keypad issues

Projects Programming
1

Hi
I'm using the keypad library to run a 4 x 4 keypad. Currently I'm picking up key presses on 3 of my 4 columns just fine. On the fourth column, the Arduino isn't picking anything up. After checking and re checking my wiring and program, I noticed that the three working column pins have a consistent voltage of about 0.5 V. However, the fourth, non functioning pin has a constantly changing voltage anywhere from 0 to a few volts.

Any ideas would be appreciated

2

The library works. That means that the problem is most likely in your code or your wiring. You didn't post either of those.

Pieter

3

That's not what I'm suggesting.

My wiring (on Arduino Nano) is column pins to pins 17-20, row pins on 13-16.

Initialisation code:

const byte rows = 3;                        //Keypad Setup
const byte cols = 4; 
char keys[rows][cols] = {
  //{'7','8','9','+'},
  {'4','5','+','-'},
  {'1','2','3','x'},
  {'0','.','=','/'}
};
byte rowPins[rows] = {14, 15, 16}; //connect to the row pinouts of the keypad
byte colPins[cols] = {17, 18, 19, 21}; //connect to the column pinouts of the keypad
Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, rows, cols );

Determining button press code:

char key = keypad.getKey();
if (key != NO_KEY){
if (count == 0) {
switch (key)
{
\continues in switch statement for all possible buttons

Thanks for your help

4

Also, the keypad is on perfboard, 16 buttons, each wired to specific column/row. I have checked and it is clear of shorts or non connects

5

macgilligan:
My wiring (on Arduino Nano) is column pins to pins 17-20

byte colPins[cols] = {17, 18, 19, 21}; //connect to the column

Oops?

6

Do you have a 3 x 4 keypad as your code says, or a 4 x 4 keypad as you claim?

7

The A6 and A7 pins on a Nano cannot be used for digital IO

8

Sorry, the code errors are simply left over from some edits I made in order to troubleshoot the problem. Not part of the issue, I just forgot to change them back. It is a 4x4 keypad, just reduced to 3 for the purposes of some different testing.

But UKHeliBob's answer seems to be the solution as it is specifically those pins that are experiencing problems.

Thanks