arduino keyboard scanner

maudio49.ino

#include "MIDIUSB.h"

bool debug = 0;
int maxPressTime = 250;
int minVelocity = 10;
int maxVelocity = 90;
int midiChannel = 0;

int keys[98] = {
  31, 29,
  56, 59,
  80, 83,
  104, 107,
  92, 95,
  68, 71,
  44, 47,
  8, 11,
  20, 23,
  58, 57,
  82, 81,
  106, 105,
  94, 93,
  70, 69,
  46, 45,
  10, 9,
  22, 21,
  48, 51,
  72, 75,
  96, 99,
  84, 87,
  60, 63,
  36, 39,
  0, 3,
  12, 15,
  50, 49,
  74, 73,
  98, 97,
  86, 85,
  62, 61,
  38, 37,
  2, 1,
  14, 13,
  55, 53,
  79, 77,
  103, 101,
  91, 89,
  67, 65,
  43, 41,
  7, 5,
  19, 17,
  54, 52,
  78, 76,
  102, 100,
  90, 88,
  66, 64,
  42, 40,
  6, 4,
  18, 16
};

unsigned long pressStart[49] = {};


bool pressed[49] = {};

void setup() {
  Serial.begin(9600);
  //select pins
  // ABC of INPUT
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(12, OUTPUT);
  // ABC of OUTPUTs
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  // from keyboard (9 pin)
  pinMode(5, INPUT); // gray
  digitalWrite(5, HIGH); // pullup
  pinMode(6, INPUT); // yellow
  digitalWrite(6, HIGH); // pullup
  // to keyboard (12 pin)
  pinMode(7, OUTPUT); // green
  pinMode(8, OUTPUT); // green
}

void set4051(int pinA, int pinB, int pinC, int channel) {
  // A = least significant bit
  // bitRead also starts from least significant bit
  digitalWrite(pinA, bitRead(channel, 0));
  digitalWrite(pinB, bitRead(channel, 1));
  digitalWrite(pinC, bitRead(channel, 2));
}

void loop() {
  for (int n = 0; n < 98; n++) {
    int k = keys[n];
    // for finding out order of keys, comment out above line and rename n to k
    int i = k / 12;
    int o = k % 12;
    int readPin = bitRead(i, 3) == 0 ? 6 : 5;
    set4051(10, 11, 12, i);
    set4051(2, 3, 4, o);
    digitalWrite(7, bitRead(o, 3));
    digitalWrite(8, !bitRead(o, 3));
    bool isConnected = digitalRead(readPin) == LOW;
    bool isDown = n % 2 == 1;
    int keyIndex = n / 2;
    int midi = keyIndex + 38;
    bool isPressed = pressed[keyIndex] == 1;

    // keypress starts
    if (isConnected && !isPressed && !isDown && !pressStart[keyIndex]) {
      if (debug) {
        Serial.print("start pressing ");
      }
      pressStart[keyIndex] = millis();
    }

    // key is now fully pressed
    if (isConnected && !isPressed && isDown) {
      unsigned long pressTime = millis() - pressStart[keyIndex];
      float f = (1 - (float)pressTime / (float)maxPressTime);
      int velocity = f * (maxVelocity - minVelocity) + minVelocity;
      if (debug) {
        Serial.print("done pressing ");
        Serial.println(f);
      }
      pressed[keyIndex] = 1;
      if (pressTime <= maxPressTime) { // min velocity?
        noteOn(midiChannel, midi, velocity);
        MidiUSB.flush();
        if (debug) {
          Serial.print("on ");
          Serial.print(midi);
          Serial.println(" ");
        }
      }
    }
    // key is now fully unpressed
    if (!isConnected && isPressed && !isDown) {
      pressed[keyIndex] = 0;
      noteOff(midiChannel, midi, 0);
      MidiUSB.flush();
      if (debug) {
        Serial.print("off ");
        Serial.print(midi);
        Serial.print(" ");
        Serial.println(" ");
      }
    }
    // key is unpressed => may include keypresses that have started but did not go down
    if (!isConnected && !isDown) {
      pressStart[keyIndex] = 0; // reset time when key is released completely
    }
  }
}

void noteOn(byte channel, byte pitch, byte velocity) {
  midiEventPacket_t noteOn = {0x09, 0x90 | channel, pitch, velocity};
  MidiUSB.sendMIDI(noteOn);
}

void noteOff(byte channel, byte pitch, byte velocity) {
  midiEventPacket_t noteOff = {0x08, 0x80 | channel, pitch, velocity};
  MidiUSB.sendMIDI(noteOff);
}

How would I change the code to work with 25 keys with out the multiplexers?

How would I change the code to work with 25 keys with out the multiplexers?

that depends on your microcontroller pins and the exact arrangement of your keyboard pcb.. I cannot write the code for you, but I could give you some hints if you get stuck with a more specific problem.

I have an 8x8 fatar keybed, using a teensy 4.1. Rows are wired to pins 40-33, cols are wired to pins 25-32. Each key has 2 switches to calculate velocity.