help with keyboard

Other Hardware General Electronics
1

So I have a 11 x 8 diode button keypad.

here is my code

const int MIDI_CHAN = 1;
const byte ROWS = 8; //four rows
const byte COLS = 11; //three columns
const int NUM_OF_BUTTONS = ROWS * COLS;
byte keys[ROWS][COLS] = {
  {0, 8,16,24,32,40,48,56,64,72,80},
  {1, 9,17,25,33,41,49,57,65,73,81},
  {2,10,18,26,34,42,50,58,66,74,82},
  {3,11,19,27,35,43,51,59,67,75,83},
  {4,12,20,28,36,44,52,60,68,76,84},
  {5,13,21,29,37,45,53,61,69,77,85},
  {6,14,22,30,38,46,54,62,70,78,86},
  {7,15,23,31,39,47,55,63,71,79,87},
};

byte rowPins[ROWS] = {7, 6, 5, 4, 3, 2, 1, 0};
byte colPins[COLS] = {9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29};//
byte MIDI_NOTE_NUMS[89] = {0, 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, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108};
void setup() {
  Serial.begin(115200);
  for(int coln=0; coln<sizeof(colPins); coln++) {
       pinMode(colPins[coln], OUTPUT); // Set the mode to OUTPUT
   }
   for(int rowNa=0; rowNa<sizeof(rowPins); rowNa++) {
       pinMode(rowPins[rowNa], INPUT_PULLUP); // Set the mode to INPUT
   }
}

void loop() {
  for (byte coln = 0; coln<sizeof(colPins); coln++) {
    digitalWrite(colPins[coln], LOW);
    for (byte rown = 0 ; rown < sizeof (rowPins) ; rown++)  
    {
        boolean state = digitalRead(rowPins [rown]);
        if(state == LOW){
          usbMIDI.sendNoteOn (MIDI_NOTE_NUMS[keys[rown][coln]], 110, MIDI_CHAN);
            Serial.print(" rown ");
           Serial.print(rown);
             Serial.print(" coln ");
           Serial.print(coln);
             Serial.print(" caracter = ");
          Serial.print(keys[rown][coln]);   
          Serial.print(" SE ACTIVO ");
          Serial.println(state);
        }
        delay(5);
        
    }
    digitalWrite (colPins[coln], HIGH) ;
  } 

}

and here is my issue:

{ row: 0,
  col: 0,
  note: 0,
  unwantedNote: { row: 0, col: 1, note: 8 } }
{ row: 0,
  col: 1,
  note: 8,
  unwantedNote: { row: 0, col: 2, note: 16 } }
{ row: 0,
  col: 2,
  note: 16,
  unwantedNote: { row: 0, col: 3, note: 24 } }
{ row: 0,
  col: 3,
  note: 24,
  unwantedNote: { row: 0, col: 4, note: 32 } }
{ row: 0,
  col: 4,
  note: 32,
  unwantedNote: { row: 0, col: 5, note: 40 } }
{ row: 0,
  col: 5,
  note: 40,
  unwantedNote: { row: 0, col: 6, note: 48 } }
{ row: 0,
  col: 6,
  note: 48,
  unwantedNote: { row: 0, col: 7, note: 56 } }
{ row: 0,
  col: 7,
  note: 56,
  unwantedNote: { row: 0, col: 8, note: 64 } }
{ row: 0,
  col: 8,
  note: 64,
  unwantedNote: { row: 0, col: 9, note: 72 } }
{ row: 0,
  col: 9,
  note: 72,
  unwantedNote: { row: 0, col: 10, note: 80 } }
{ row: 0,
  col: 10,
  note: 80,
  unwantedNote: { row: 0, col: 0, note: 0 } }

whenever I press a key on the row 0 there are not one but two key presses detected.
one for row 0 col x and another one for row 0 col x + 8.
there are no shorts, I verified with a tester. any idea what might be the cause?

2

Not obvious. Take a photo in daylight outside and show us what it looks like.

3

@OP

Are you using Arduino MEGA?

You have 8 Row Lines for your Keypad and these are: R0 (Row-0), R1, ..., R7
Which Digital Pin out-of {7, 6, 5, 4, 3, 2, 1, 0} are you considering for R0? Is it DPin-0 or DPin-7?

Can you avoid using DPin-0 and DPin-1 as these two pins are driving the Serial Monitor/IDE. I recommend to use this set: {9, 8, 7, 6, 5, 4, 3, 2}.] for the row lines of the Keypad.

You have 11 Column Lines for your Keypad and these are: C0 (Col-0), C1, ..., C10
Which Digital Pin out-of {9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29} are you considering for C0? If you decide to use DPin-9 for Row, let us take 31 for Col. Now, the new set is: {~~9,~~11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31}. Is it DPin-31 or DPin-11 are you considering for C0?

Is K00 (Key across R0 and C0) across 2-31 or 9-11?

BTW: Why are you not taking the advantage of Keypad.h Library for your Keypad?