added simple arduino firmware

firmware_arduino/hackpad_simple/hackpad_simple.ino

@@ -0,0 +1,66 @@
+//=============================================================================
+// iR Hackpad Demo Firmware
+// Compile for Arduino Leonardo
+//=============================================================================
+
+// The Arduino Keyboard library creates a HID keyboard interface to send keyboard scancodes to the host.
+// For convenience, the class takes ASCII characters via Keyboard::write(), which are automatically
+// converted to the corresponding keboard scan-codes according to the keyboard layout passed to
+// Keyboard::begin(). On the host side, the scan-codes are again converted to characters by the OS.
+#include "Keyboard.h"
+
+//=============================================================================
+// Our key matrix (see schematics)
+const int N_rows = 5;
+const int N_cols = 4;
+const int gpio_rows[N_rows] = { 6, 7, 8, 9, 5 };
+const int gpio_cols[N_cols] = { 15, 14, 16, 10 };
+
+// Key function assignment: ASCII characters or special function codes (see Keyboard.h)
+const int key_matrix[N_rows][N_cols] = {
+  {'a', 'b', 'c', 'd'},  // 4x4 keypad
+  {'e', 'f', 'g', 'h'},
+  {'i', 'j', 'k', 'l'},
+  {'m', 'n', 'o', 'p'},
+  {'_', '_', '_', 'x'}   // rotery encoder button
+};
+int is_pressed[N_rows][N_cols] = { 0 };
+
+const uint32_t KEY_SCAN_DELAY_US = 100;  // Delay between row scans
+
+//=============================================================================
+
+void setup()
+{
+  for (int col=0; col<N_cols; col++) {
+    pinMode(gpio_cols[col], INPUT_PULLUP);  // Key matrix columns as inputs
+  }
+  for (int row=0; row<N_rows; row++) {
+    digitalWrite(gpio_rows[row], HIGH);
+    pinMode(gpio_rows[row], OUTPUT);  // Key matrix rows as outputs
+  }
+  Keyboard.begin(KeyboardLayout_de_DE);
+  Serial.begin(9600);  // Open serial port to host, so the IDE can reset the device for reprogramming
+}
+
+//=============================================================================
+
+void loop()
+{
+  for (int row=0; row<N_rows; row++) {
+    digitalWrite(gpio_rows[row], LOW);
+    for (int col=0; col<N_cols; col++) {
+      if (digitalRead(gpio_cols[col]) == LOW){
+        is_pressed[row][col] = true;
+        Keyboard.press(key_matrix[row][col]);
+        } else if (is_pressed[row][col]) {
+          Keyboard.release(key_matrix[row][col]);
+          is_pressed[row][col] = false;
+        }
+      delayMicroseconds(KEY_SCAN_DELAY_US);  // Give the column inputs time to reach HIGH state (slow recharge via weak pullups)
+    }
+    digitalWrite(gpio_rows[row], HIGH);
+  }
+}
+
+//=============================================================================