Code that sends ctrl key, at least.

TODO: Send key up and key down appropriately

emacs-keyboard/emacs-keyboard.ino

@@ -1,9 +1,44 @@
+// #include "Keyboard.h"
+// #include "HID.h"
+
+// https://www.arduino.cc/en/Reference/KeyboardBegin
+// https://www.arduino.cc/en/Tutorial/KeyboardMessage
+// https://www.arduino.cc/en/Tutorial/KeyboardReprogram
+
+// http://www.cplusplus.com/doc/tutorial/structures/
+struct Key {
+  int pin;  
+  char keyCode;
+  boolean wasPushed;
+};
+
+const int NUM_OF_KEYS = 4;
+Key keys[NUM_OF_KEYS];
+
 void setup() {
-  // put your setup code here, to run once:
+  // Initialize key data
+  // { buttonPin, keyCode }
+  keys[0] = { 2, KEY_LEFT_CTRL };
+  keys[1] = { 3, KEY_LEFT_ALT };
+  keys[2] = { 4, KEY_LEFT_SHIFT };
+  keys[3] = { 5, KEY_BACKSPACE };
+  
+  // make pins inputs and turn on the 
+  // pullup resistor so they go high unless
+  // connected to ground:
+  for(int i = 0; i < NUM_OF_KEYS; i++) {
+    pinMode(keys[i].pin, INPUT_PULLUP);
+  }
 
+  Keyboard.begin();
 }
 
 void loop() {
-  // put your main code here, to run repeatedly:
-
+  for(int i = 0; i < NUM_OF_KEYS; i++) {
+    if(digitalRead(keys[i].pin) == LOW) { // If the key is pressed...
+      Keyboard.press(keys[i].keyCode); // Send the key
+      delay(100);
+      Keyboard.releaseAll();
+    }
+  }
 }