Arduino key matrix example

int8_t rowpins[] = {16, 15, 14};
int8_t colpins[] = {13, 12, 11, 10, 9, 8};
int8_t rotatoryPins[] = {7, 6, 5, 4};

bool btnStatus[6 * 3]; // We have 6(cols) * 3(rows) buttons/switches
int8_t rotatoryStatus[2 * 3]; // We have 2 rotatory buttons in every row (3)

void setup() {
    Serial.println(9600);
    // put your setup code here, to run once:
    for(uint8_t row = 0; row < (sizeof(rowpins) / sizeof(rowpins[0])); row++) {
        pinMode(rowpins[row], OUTPUT);
        digitalWrite(rowpins[row], HIGH);
    }
    for(uint8_t col = 0; col < (sizeof(colpins) / sizeof(colpins[0])); col++) {
        pinMode(colpins[col], INPUT_PULLUP);
    }
    for(uint8_t i = 0; i < (sizeof(rotatoryPins) / sizeof(rotatoryPins[0])); i++) {
        pinMode(rotatoryPins[i], INPUT_PULLUP);
    }
}

void switchUpdate(uint8_t row, uint8_t col, bool status) {
    Serial.print("The switch/button at col ");
    Serial.print(col);
    Serial.print(" and row ");
    Serial.print(row);
    Serial.print(" was updated to: ");
    Serial.println(status);
}

void rotatoryUpdate(uint8_t row, uint8_t col, uint8_t newVal, uint8_t oldVal) {
    Serial.print("The rotatory at col ");
    Serial.print(col);
    Serial.print(" and row ");
    Serial.print(row);
    Serial.print(" was updated to ");
    Serial.print(newVal);
    Serial.print(" from ");
    Serial.println(oldVal);
}

void checkInput() {
    for(uint8_t row = 0; row < (sizeof(rowpins) / sizeof(rowpins[0])); row++) {
        digitalWrite(rowpins[row], LOW);
        uint8_t partialIndex = row * (sizeof(colpins) / sizeof(colpins[0]));

        // Check normal buttons
        for(uint8_t col = 0; col < (sizeof(colpins) / sizeof(colpins[0])); col++) {
            uint8_t index = partialIndex + col;
            bool status = digitalRead(colpins[col]) == LOW ? true : false;
            bool old_status = btnStatus[index];

            if(status != old_status) {
                switchUpdate(row, col, status);
                btnStatus[index] = status;
            }

        }
        // Check rotatory encoders

        for(uint8_t i = 0; i < (sizeof(rotatoryPins) / sizeof(rotatoryPins[0])); i+=2) {
            uint8_t index = partialIndex + (i / 2);
            uint8_t status =
                (digitalRead(rotatoryPins[i]) == LOW ? 1 : 0) ^
                (digitalRead(rotatoryPins[i + 1]) == LOW ? 2 : 0);
            bool old_status = rotatoryStatus[index];

            if(status != old_status) {
                rotatoryUpdate(row, i / 2, status, old_status);
                rotatoryStatus[index] = status;
            }
        }
        digitalWrite(rowpins[row], HIGH); // reset this row
    }
}

void loop() {
    // put your main code here, to run repeatedly:
    checkInput();
}