// https://wokwi.com/projects/411181034370782209
//
// From https://wokwi.com/projects/410325174113969153
// by https://wokwi.com/makers/maverick
// per https://discord.com/channels/787627282663211009/1289692132776476853/1289786828915740704
//
uint32_t getKeys() {
  uint32_t retval = 0;
  for (int i = 2; i < 6; ++i) {
    pinMode(i, OUTPUT);
    digitalWrite(i, LOW);
    for (int j = 6; j < 10; ++j) {
      pinMode(j, INPUT_PULLUP);
      retval <<= 1;
      if (!digitalRead(j)) {
        retval |= 0b1;
        // Serial.print(j - 5);
        // Serial.print(',');
        // Serial.print(i - 1);
        // Serial.print("P ");
        delay(100);
      }
    }
    digitalWrite(i, HIGH);
  }
  return retval;
}

void setup() {
  Serial.begin(115200);
}

void loop() {
  static uint32_t last = 0;
  uint32_t nowKey = getKeys();
  if(nowKey != last){
    Serial.print(nowKey,BIN);
    Serial.print(':');
    Serial.print((nowKey ^ last),BIN);
    Serial.println(' ');
    last = nowKey;
  }
  delay(10);
}