// Keyboard Matrix Tutorial Example
// baldengineer.com
// CC BY-SA 4.0
 
// JP1 is an input
byte rows[] = {2,3,4};
const int rowCount = sizeof(rows)/sizeof(rows[0]);

// JP2 and JP3 are outputs
byte cols[] = {8,9,10};
const int colCount = sizeof(cols)/sizeof(cols[0]);

byte keys[colCount][rowCount];

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

	for(int x=0; x<rowCount; x++) {
		Serial.print(rows[x]); Serial.println(" as input");
		pinMode(rows[x], INPUT);
	}

	for (int x=0; x<colCount; x++) {
		Serial.print(cols[x]); Serial.println(" as input-pullup");
		pinMode(cols[x], INPUT_PULLUP);
	}
		
}

void readMatrix() {
	// iterate the columns
	for (int colIndex=0; colIndex < colCount; colIndex++) {
		// col: set to output to low
		byte curCol = cols[colIndex];
		pinMode(curCol, OUTPUT);
		digitalWrite(curCol, LOW);

		// row: interate through the rows
		for (int rowIndex=0; rowIndex < rowCount; rowIndex++) {
			byte rowCol = rows[rowIndex];
			pinMode(rowCol, INPUT_PULLUP);
			keys[colIndex][rowIndex] = digitalRead(rowCol);
			pinMode(rowCol, INPUT);
		}
		// disable the column
		pinMode(curCol, INPUT);
	}
}

void printMatrix() {
	for (int rowIndex=0; rowIndex < rowCount; rowIndex++) {
		if (rowIndex < 10)
			Serial.print(F("0"));
		Serial.print(rowIndex); Serial.print(F(": "));

		for (int colIndex=0; colIndex < colCount; colIndex++) {	
			Serial.print(keys[colIndex][rowIndex]);
			if (colIndex < colCount)
				Serial.print(F(", "));
		}	
		Serial.println("");
	}
	Serial.println("");
}

void loop() {
	readMatrix();
	if (Serial.read()=='!')
		printMatrix();
}