Make it a 4-button working keyboardHEADmaster

Thanks to some electrical engineering assistance from a good friend, the
2×2 button keyboard is now a reality.

2 files changed, 94 insertions, 35 deletions

diff --git a/dactylino.cpp b/dactylino.cpp
index 31e217e..82cb9f6 100644
--- a/dactylino.cpp
+++ b/dactylino.cpp
@@ -27,49 +27,107 @@
  * to the Arduino UNO board.
  */
 
-const unsigned int LED_PIN = 13;
-const unsigned int BUTTON_PIN = 7;
-const unsigned int PAUSE = 500; /* ms */
+/**
+ * 1. Set COL to INPUT_PULLUP mode (it reads HIGH by default)
+ * 2. But diode on the row (direction?) [Leave it out for now...]
+ * 3. Program Row to be LOW and OUTPUT, everything else an input
+ * 4. Then column 1 should read LOW when button is pressed (LOW)
+ *
+ *  - In sequence, set one row to OUTPUT and LOW, all other rows to INPUT
+ *  - check each column
+ *  - Any column reading LOW is pressed
+ *  - set row back to INPUT and move to next row
+ */
 
-int last_state = HIGH;
-int current_state;
-int counter = 0;
+#define DEBOUNCE_TIME 10
 
-void setup() {
-	Serial.begin(9600);
-	pinMode(LED_PIN, OUTPUT);
-	pinMode(BUTTON_PIN, INPUT_PULLUP);
-}
+const byte ROWS = 2;
+const byte COLS = 2;
+const byte TOTAL_KEYS = ROWS * COLS;
 
-void loop() {
+const byte row_pins[ROWS] = {2, 3};
+const byte col_pins[COLS] = {6, 7};
 
-	current_state = digitalRead(BUTTON_PIN);
+// All the letters you need
+const char letters[TOTAL_KEYS] = {'A', 'B', 'C', 'D'};
 
-	if (last_state == HIGH && current_state == LOW) {
-		digitalWrite(LED_PIN, HIGH);
-	}
+void setup() {
+	byte i;
+	Serial.begin(9600);
 
-	if (last_state == LOW && current_state == HIGH) {
-		digitalWrite(LED_PIN, LOW);
-		Serial.print("Click: ");
-		Serial.print(++counter);
-		Serial.println();
-	}
+	for (i = 0; i < COLS; i++)
+		pinMode(col_pins[i], INPUT_PULLUP);
 
+	for (i = 0; i < ROWS; i++)
+		pinMode(row_pins[i], INPUT);
+}
 
-	last_state = current_state;
+/**
+ * Need structure to track key state: last known key setting and last time it
+ * toggled its state
+ */
+unsigned long last_key_time[TOTAL_KEYS];
 
-	/*
-	digitalWrite(LED_PIN, HIGH);
-	delay(PAUSE);
-	digitalWrite(LED_PIN, LOW);
-	delay(PAUSE);
+/**
+ * TODO Expand this to an array-back bitmap (only really relevant when we move
+ * beyond 32 keys)
+ */
+unsigned char last_key_setting = 0;
+
+/* TODO Remove the counter, just for debugging */
+unsigned long counter = 0;
 
-	counter = (counter + 1) % 10;
-	Serial.print(".");
-	if (counter == 0)
-		Serial.println("");
-	*/
+void loop() {
+	bool pressed;
+	bool last;
+	byte row, col, k;
+
+	unsigned long now; /* For debouncing */
+
+	now = millis();
+	k = 0;
+	for (row = 0; row < ROWS; row++) {
+		/* Set pin to output, and set it LOW */
+		pinMode(row_pins[row], OUTPUT);
+		digitalWrite(row_pins[row], LOW);
+
+		/* Scan all columns */
+		for (col = 0; col < COLS; col++) {
+			if (now - last_key_time[k] < DEBOUNCE_TIME) {
+				k++;
+				continue;
+			}
+
+			/* Read the key */
+			pressed = digitalRead(col_pins[col]) == LOW;
+			last = (last_key_setting & (1 << k)) != 0;
+
+			/* Check the k'th bit */
+			if (pressed != last) {
+				/* Changed */
+				last_key_time[k] = now;
+				/* Toggle the bit */
+				last_key_setting ^= (1 << k);
+
+				if (pressed) {
+					//Serial.print("Key pressed:  (");
+					//Serial.print("")
+				} else {
+					Serial.println(letters[k]);
+					// Serial.print("Key released: (");
+					// Serial.print("row=");
+					// Serial.print(row);
+					// Serial.print(",col=");
+					// Serial.print(col);
+					// Serial.println(")");
+				}
+			}
+
+			/* Consider next key */
+			k++;
+		}
+		pinMode(row_pins[row], INPUT);
+	}
 }
 
 // Declared weak in Arduino.h to allow user redefinitions.
diff --git a/t/test.py b/t/test.py
index c7a1018..e42edbb 100755
--- a/t/test.py
+++ b/t/test.py
@@ -5,9 +5,10 @@ import serial
 def main():
     with serial.Serial('/dev/ttyACM0', 9600, timeout=10) as ser:
         while True:
-            b = ser.read()
+            b = ser.readline()
             if b:
-                print(b)
+                #print(b)
+                print(b.decode('ascii').strip())
 
 if __name__ == '__main__':
     main()