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Cameron Coward
Published © CC BY-NC-SA

64-Key Prototyping Keyboard Matrix for Arduino

A simple PCB keyboard that you can easily use for your Arduino project. Fully-customizable code provided!

IntermediateFull instructions provided1 hour25,537
64-Key Prototyping Keyboard Matrix for Arduino

Things used in this project

Hardware components

Arduino UNO
Arduino UNO
×1
1N4148 – General Purpose Fast Switching
1N4148 – General Purpose Fast Switching
×64
Tactile Switch, Top Actuated
Tactile Switch, Top Actuated
×64
Pin headers
×1
74HC595 Shift Register
×1

Software apps and online services

Arduino IDE
Arduino IDE

Hand tools and fabrication machines

Soldering iron (generic)
Soldering iron (generic)

Story

Read more

Custom parts and enclosures

Custom PCB Gerber Files

Upload the entire .zip file to your PCB fabrication service

Schematics

PCB schematic

Code

ProtoKeyboardV1.1-Shifted.ino

Arduino
No preview (download only).

ProtoKeyboardV1-Bits.ino

Arduino
Updated Arduino Code
/*    Sketch for Prototyping Keyboard V1.2
 *    by Cameron Coward 1/30/21
 *    
 *    Tested on Arduino Uno. Requires custom PCB
 *    and a 74HC595 shift register.
 *    
 *    More info: https://www.hackster.io/cameroncoward/64-key-prototyping-keyboard-matrix-for-arduino-4c9531
 */

const int rowData = 2; // shift register Data pin for rows
const int rowLatch = 3; // shift register Latch pin for rows
const int rowClock = 4; // shift register Clock pin for rows

// these are our column input pins. Pin 0 and Pin 1 are not used,
// because they cause issues (presumably because they're TX and RX)
const int colA = A0; 
const int colB = A1; 
const int colC = A2; 
const int colD = A3;
const int colE = A4;
const int colF = A5;
const int colG = 5;
const int colH = 6;


// shiftRow is the required shift register byte for each row, rowState will contain pressed keys for each row
const byte shiftRow[] = {B01111111, B10111111, B11011111, B11101111, B11110111, B11111011, B11111101, B11111110};
byte rowState[] = {B00000000, B00000000, B00000000, B00000000, B00000000, B00000000, B00000000, B00000000};
byte prevRowState[] = {B00000000, B00000000, B00000000, B00000000, B00000000, B00000000, B00000000, B00000000};

// ASCII codes for keys with no modifiers pressed. Modifiers are NULL (0),
// because we will check those separately and their values should not be printed.
const char key[] = {
  0, 49, 50, 51, 52, 53, 54, 55,
  56, 57, 48, 45, 61, 0, 9, 113,
  119, 101, 114, 116, 121, 117, 105, 111,
  112, 91, 93, 92, 7, 97, 115, 100,
  102, 103, 104, 106, 107, 108, 59, 39,
  0, 0, 122, 120, 99, 118, 98, 110,
  109, 44, 46, 47, 0, 0, 0, 0,
  32, 0, 0, 0, 0, 0, 0, 0
};

// ASCII codes for keys with shift pressed AND caps is active
const char capsShiftKey[] = {
  0, 33, 64, 35, 36, 37, 94, 38,
  42, 40, 41, 95, 43, 0, 9, 113,
  119, 101, 114, 116, 121, 117, 105, 111,
  112, 123, 125, 124, 7, 97, 115, 100,
  102, 103, 104, 106, 107, 108, 58, 22,
  0, 0, 122, 120, 99, 118, 98, 110,
  109, 44, 46, 47, 0, 0, 0, 0,
  32, 0, 0, 0, 0, 0, 0, 0
};

// ASCII codes for keys with shift pressed.
const char shiftKey[] = {
  0, 33, 64, 35, 36, 37, 94, 38,
  42, 40, 41, 95, 43, 0, 9, 81,
  87, 69, 82, 84, 89, 85, 73, 79,
  80, 123, 125, 124, 7, 65, 83, 68,
  70, 71, 72, 74, 75, 76, 58, 22,
  0, 0, 90, 88, 67, 86, 66, 78,
  77, 44, 46, 47, 0, 0, 0, 0,
  32, 0, 0, 0, 0, 0, 0, 0
};

// ASCII codes for keys with ctrl pressed.
const char ctrlKey[] = {
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 9, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  32, 0, 0, 0, 0, 0, 0, 0
};

// ASCII codes for keys with spcl pressed.
const char spclKey[] = {
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0
};

// ASCII codes for keys with alt pressed.
const char altKey[] = {
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0
};

// ASCII codes for keys with fn pressed.
const char fnKey[] = {
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0
};

// ASCII codes for keys with caps is active
const char capsKey[] = {
  0, 49, 50, 51, 52, 53, 54, 55,
  56, 57, 48, 45, 61, 0, 9, 81,
  87, 69, 82, 84, 89, 85, 73, 79,
  80, 91, 93, 92, 7, 65, 83, 68,
  70, 71, 72, 74, 75, 76, 59, 39,
  0, 0, 90, 88, 67, 86, 66, 78,
  77, 44, 46, 47, 0, 0, 0, 0,
  32, 0, 0, 0, 0, 0, 0, 0
};

long previousKeyboardMicros = 0;        // will store last time keyboard was checked
 
// the follow variables is a long because the time, measured in miliseconds,
// will quickly become a bigger number than can be stored in an int.
long keyboardInterval = 500;           // interval at which to check keyboard (microseconds)

int rowToCheck = 0; // We check one row per loop of checkKeyboard(), this combined with keyboardInterval 
                    // gives the shiftRegister time to fully update between row checks

bool caps = false;  // is caps lock on?
bool shift = false; // is either left or right shift pressed?
bool capsShift = false; // are shift AND caps active?
bool ctrl = false; // is the ctrl key pressed?
bool spcl = false;  // is the spcl key pressed?
bool alt = false; // is the alt key pressed?
bool fn = false;  // is the function key pressed?

void setup() {
  Serial.begin(9600);

  // setup all column pin as inputs with internal pullup resistors
  pinMode(colA, INPUT_PULLUP); 
  pinMode(colB, INPUT_PULLUP);
  pinMode(colC, INPUT_PULLUP);
  pinMode(colD, INPUT_PULLUP);
  pinMode(colE, INPUT_PULLUP); 
  pinMode(colF, INPUT_PULLUP);
  pinMode(colG, INPUT_PULLUP);
  pinMode(colH, INPUT_PULLUP);

  // the outputs needed to control the 74HC595 shift register
  pinMode(rowLatch, OUTPUT);
  pinMode(rowClock, OUTPUT);
  pinMode(rowData, OUTPUT);

  updateShiftRegister(B11111111); // make sure shift register starts at all HIGH
}

void loop() {
 mainTimer();
}

void mainTimer() {

  unsigned long currentMicros = micros(); // how many microseconds has the Arduino been running?
  
  if(currentMicros - previousKeyboardMicros > keyboardInterval) { // if elapsed time since last check exceeds the interval
    // save the last time the keyboard was checked
    previousKeyboardMicros = currentMicros;   
 
    checkKeyboard(); // check all of the keys and print out the results to serial
  }
}

void updateShiftRegister(byte row) {
  //this function sets the shift register according to the byte that was passed to it
 
  digitalWrite(rowLatch, LOW); // set latch to low so we can write an entire byte at once
  shiftOut(rowData, rowClock, MSBFIRST, row);  // write that byte
  digitalWrite(rowLatch, HIGH); // set latch back to high so it shift register will remain stable until next change
}

void checkKeyboard() {

  // set the shift register to the current row's byte value, from the shiftRow[] byte array
  updateShiftRegister(shiftRow[rowToCheck]);

  // Check each column
  if (digitalRead(colA) == LOW) {
    bitSet(rowState[rowToCheck], 0);
  } else {
    bitClear(rowState[rowToCheck], 0);
  }
  
  if (digitalRead(colB) == LOW) {
    bitSet(rowState[rowToCheck], 1);
  } else {
    bitClear(rowState[rowToCheck], 1);
  }
  
  if (digitalRead(colC) == LOW) {
    bitSet(rowState[rowToCheck], 2);
  } else {
    bitClear(rowState[rowToCheck], 2);
  }
  
  if (digitalRead(colD) == LOW) {
    bitSet(rowState[rowToCheck], 3);
  } else {
    bitClear(rowState[rowToCheck], 3);
  }
  
  if (digitalRead(colE) == LOW) {
    bitSet(rowState[rowToCheck], 4);
  } else {
    bitClear(rowState[rowToCheck], 4);
  }
  
  if (digitalRead(colF) == LOW) {
    bitSet(rowState[rowToCheck], 5);
  } else {
    bitClear(rowState[rowToCheck], 5);
  }
  
  if (digitalRead(colG) == LOW) {
    bitSet(rowState[rowToCheck], 6);
  } else {
    bitClear(rowState[rowToCheck], 6);
  }
  
  if (digitalRead(colH) == LOW) {
    bitSet(rowState[rowToCheck], 7);
  } else {
    bitClear(rowState[rowToCheck], 7);
  }

  // set all shift register pins to HIGH, this keeps values from "bleeding" over to the next loop
  updateShiftRegister(B11111111);

  rowToCheck = rowToCheck + 1; // iterate to next row

  // after checking the 8th row, check the states (button presses) and then start over on the 1st row
  if (rowToCheck > 7 ) {
    checkPressedKeys();
    rowToCheck = 0;
  }
}

void checkPressedKeys() {
  // check if either shift key is pressed
  if (bitRead(rowState[5], 1) | bitRead(rowState[6], 4)) {
    shift = true;
  } else {
    shift = false;
  }

  // check if either ctrl key is pressed
  if (bitRead(rowState[6], 5) | bitRead(rowState[7], 3)) {
    ctrl = true;
  } else {
    ctrl = false;
  }

  // check if either spcl key is pressed
  if (bitRead(rowState[6], 6) | bitRead(rowState[7], 2)) {
    spcl = true;
  } else {
    spcl = false;
  }

  // check if either alt key is pressed
  if (bitRead(rowState[6], 7) | bitRead(rowState[7], 1)) {
    alt = true;
  } else {
    alt = false;
  }

  // check if FN key is pressed
  if (bitRead(rowState[7], 4)) {
    fn = true;
  } else {
    fn = false;
  }

  // check caps is active and shift is pressed
  if (shift == true && caps == true) {
    capsShift = true;
  } else {
    capsShift = false;
  }
  
  for (int i = 8; i >= 0; i--) {                    // iterate through each row
    for (int j = 7; j >= 0; j--) {                  // iterate through each bit in that row
      
      bool newBit = bitRead(rowState[i], j);             // check the state of that bit
      bool prevBit = bitRead(prevRowState[i], j);         // check the previous state of that bit
      
      if ((newBit == 1) && (prevBit == 0)) {                       // only allows button press if state has changed to true
          int thisChar = (i * 8) + j;               // calculate which position in char array to select

          if (capsShift == true) {
            processKey(capsShiftKey[thisChar]);
          } else if (shift == true) {
            processKey(shiftKey[thisChar]);
          } else if (ctrl == true) {
            processKey(ctrlKey[thisChar]);
          } else if (alt == true) {
            processKey(altKey[thisChar]);
          } else if (spcl == true) {
            processKey(spclKey[thisChar]);
          } else if (fn == true) {
            processKey(fnKey[thisChar]);
          } else if (caps == true) {
            processKey(capsKey[thisChar]);
          } else {
            processKey(key[thisChar]);     
          }
      }
      
      if (newBit == 1) {
          bitSet(prevRowState[i], j);     // set previous bit state to true if a key is pressed
      } else {
          bitClear(prevRowState[i], j);   // set previous bit state to false if key isn't pressed, so it can be pressed again
      }
    }
  }
}

void processKey(char receivedKey) {
  if (receivedKey == 7) {                 // check for special functions in the same way as caps (add new "else if" statements)
    caps = !caps;
  } else {
    Serial.print(receivedKey);            // if char does not correspond to a special function, simply print that char
  }
}

Credits

Cameron Coward

Cameron Coward

18 projects • 1411 followers
Writer for Hackster News. Proud husband and dog dad. Maker and serial hobbyist. Check out my YouTube channel: Serial Hobbyism

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