Added 4x4 I2C Arduino Code under firmwares/

firmwares/keypad_4x4_i2c_nano_backpack.ino

@@ -0,0 +1,122 @@
+#include <Wire.h>
+
+/**
+ *
+ * This is a derivative of the Keypad 3x4 I2C Nano Backpack.
+ * Much of the code is the same, however due to an additional 8th pin, some of
+ * the code has to be modified to suit 16 buttons instead of 12.
+ * 
+ */
+
+#define DEBUG_MODE 0
+
+// Address Pins
+#define AD0 11
+#define AD1 12
+
+// I2C Defaults
+#define I2C_DEFAULT_ADDRESS 0x0A
+#define I2C_BUFFER_SIZE 2
+
+byte buffer[I2C_BUFFER_SIZE];
+
+int addressPins[] = { AD0, AD1 };
+int address = I2C_DEFAULT_ADDRESS;
+
+int pins[8] = {8, 7, 6, 5, 4, 3, 2, 9};
+
+void resetPins() {
+  for (int i = 0; i < 8; i++) {
+    pinMode(pins[i], INPUT);
+    digitalWrite(pins[i], HIGH);
+  }
+}
+
+void setup() {
+
+  int offset = 0;
+
+  for (int i = 0; i < 2; i++) {
+    pinMode(addressPins[i], INPUT);
+    if (digitalRead(addressPins[i])) {
+      offset |= 1 << i;
+    }
+  }
+
+  address += offset;
+
+  #if DEBUG_MODE
+   Serial.begin(9600);
+  #endif
+
+  resetPins();
+
+  Wire.begin(address);
+  Wire.onRequest(onRequest);
+}
+
+void loop() {
+  int state = read();
+  // int index = toIndex(state);
+
+  // if (state == 0) {
+  //   index = 0xFF;
+  // }
+
+  // #if DEBUG_MODE
+  // if (index != 0xff) {
+  //   Serial.println(index);
+  // }
+  // #endif
+
+  // buffer[0] = index >> 8;
+  // buffer[1] = index & 0xFF;
+
+  buffer[0] = state >> 8;
+  buffer[1] = state & 0xFF;
+
+  delay(10);
+}
+
+int toIndex(int bits) {
+  for (int i = 0; i < 16; i++) {
+    if (bits & (1 << i)) {
+      return i;
+    }
+  }
+}
+
+int read() {
+  // 2, 7, 6, 4
+  // 3, 1, 5, 9
+  int rowPins[4] = {7, 2, 3, 5};
+  int colPins[4] = {6, 8, 4, 9};
+  int state = 0;
+
+
+  resetPins();
+
+  for (int row = 0; row < 4; row++) {
+    // "Open" the row for reading...
+    // Set the row to OUTPUT and put all pins LOW
+    pinMode(rowPins[row], OUTPUT);
+    digitalWrite(rowPins[row], LOW);
+    // Iterate across the columns in this row
+    for (int col = 0; col < 4; col++) {
+      // Read and update the state byte
+      if (!digitalRead(colPins[col])) {
+        state |= 1 << ((row + 1) * 4 + (col + 1) - 5);
+      }
+    }
+    // "Close" the row...
+    // Set the row to INPUT and put all pins HIGH
+    pinMode(rowPins[row], INPUT);
+    digitalWrite(rowPins[row], HIGH);
+  }
+
+  return state;
+}
+
+void onRequest() {
+  Wire.write(buffer, 2);
+}