Grezzo · December 11, 2015 15:00
diff --git a/Arduino Duo Monitor-Auto-Rotate.ino b/Arduino Duo Monitor-Auto-Rotate.ino
 /*
 * Monitor-Auto-Rotate v1
 * 
 * Sketch that will change display orientation by using usb keyboard emultaion to  
 * press Ctrl+Alt+Up-Arrow or Ctrl+Alt+Right-Arrow (which are the default hotkeys
 * to rotate the display on windows systems with Intel graphics drivers) when it
 * senses (using a reed switch and a magnet) that the monitor has been physically
 * rotated.
 * 
 * Requires updating the Arduino's atmega8u2 USB firmware so that it can emulate
 * a USB keyboard (this stops you from being able to upload sketches, so you must
 * upoad the sketch before changing the firmware)
 * 
 * USB HID firmware can be downloaded from:
 * http://hunt.net.nz/users/darran/weblog/b3029/Arduino_UNO_Keyboard_HID_version_03.html
 * 
 * The circuit:
 * Reed switch attached from pin 12 to GND
 * Magnet should pull reed switch closed when monitor is in portrait position
 */

 #define KEY_LEFT_CTRL 0b00000001
 #define KEY_LEFT_ALT 0b00000100
 #define KEY_UP_ARROW 82
 #define KEY_LEFT_ARROW 80

 const int switchPin = 12;    // the number of the pushbutton pin

 int switchState;     // the current reading from the switch pin
 int lastSwitchState; // the previous reading from the switch pin
 long lastDebounceTime = 0;  // the last time the switch pin was toggled
 long debounceDelay = 50;    // the debounce time

 uint8_t buf[8] = {0};   /* Keyboard report buffer */

 void setup() {
  pinMode(switchPin, INPUT_PULLUP);
  Serial.begin(9600);
 }

 void sendKeyPress(byte modifier, byte key) {
  buf[0] = modifier;
  buf[2] = key;
  Serial.write(buf, 8); // Send keypress
  delay(100); //Give host time to read keypress
  buf[0] = 0;
  buf[2] = 0;
  Serial.write(buf, 8);  // Release key  
 }

 void loop() {
  // read the state of the switch into a local variable:
  int reading = digitalRead(switchPin);

  // check to see if you just pressed the button
  // (i.e. the input went from LOW to HIGH),  and you've waited
  // long enough since the last press to ignore any noise:

  // If the switch changed, due to noise or pressing:
  if (reading != lastSwitchState) {
    // reset the debouncing timer
    lastDebounceTime = millis();
  }

  if ((millis() - lastDebounceTime) > debounceDelay) {
    // whatever the reading is at, it's been there for longer
    // than the debounce delay, so take it as the actual current state:

    // if the button state has changed:
    if (reading != switchState) {
      switchState = reading;

      if (switchState == HIGH) {
        //Send hotkey for normal (landscape) orientation
        sendKeyPress(KEY_LEFT_CTRL + KEY_LEFT_ALT, KEY_UP_ARROW);
        //Serial.println("SEND UP");
      } else {
        //Send hotkey for portrait orientation
        sendKeyPress(KEY_LEFT_CTRL + KEY_LEFT_ALT, KEY_LEFT_ARROW);
        //Serial.println("SEND LEFT");
      }
    }
  }

  // save the reading.  Next time through the loop,
  // it'll be the lastSwitchState:
  lastSwitchState = reading;
 }
	/*
	* Monitor-Auto-Rotate v1
	*
	* Sketch that will change display orientation by using usb keyboard emultaion to
	* press Ctrl+Alt+Up-Arrow or Ctrl+Alt+Right-Arrow (which are the default hotkeys
	* to rotate the display on windows systems with Intel graphics drivers) when it
	* senses (using a reed switch and a magnet) that the monitor has been physically
	* rotated.
	*
	* Requires updating the Arduino's atmega8u2 USB firmware so that it can emulate
	* a USB keyboard (this stops you from being able to upload sketches, so you must
	* upoad the sketch before changing the firmware)
	*
	* USB HID firmware can be downloaded from:
	* http://hunt.net.nz/users/darran/weblog/b3029/Arduino_UNO_Keyboard_HID_version_03.html
	*
	* The circuit:
	* Reed switch attached from pin 12 to GND
	* Magnet should pull reed switch closed when monitor is in portrait position
	*/

	#define KEY_LEFT_CTRL 0b00000001
	#define KEY_LEFT_ALT 0b00000100
	#define KEY_UP_ARROW 82
	#define KEY_LEFT_ARROW 80

	const int switchPin = 12; // the number of the pushbutton pin

	int switchState; // the current reading from the switch pin
	int lastSwitchState; // the previous reading from the switch pin
	long lastDebounceTime = 0; // the last time the switch pin was toggled
	long debounceDelay = 50; // the debounce time

	uint8_t buf[8] = {0}; /* Keyboard report buffer */

	void setup() {
	pinMode(switchPin, INPUT_PULLUP);
	Serial.begin(9600);
	}

	void sendKeyPress(byte modifier, byte key) {
	buf[0] = modifier;
	buf[2] = key;
	Serial.write(buf, 8); // Send keypress
	delay(100); //Give host time to read keypress
	buf[0] = 0;
	buf[2] = 0;
	Serial.write(buf, 8); // Release key
	}

	void loop() {
	// read the state of the switch into a local variable:
	int reading = digitalRead(switchPin);

	// check to see if you just pressed the button
	// (i.e. the input went from LOW to HIGH), and you've waited
	// long enough since the last press to ignore any noise:

	// If the switch changed, due to noise or pressing:
	if (reading != lastSwitchState) {
	// reset the debouncing timer
	lastDebounceTime = millis();
	}

	if ((millis() - lastDebounceTime) > debounceDelay) {
	// whatever the reading is at, it's been there for longer
	// than the debounce delay, so take it as the actual current state:

	// if the button state has changed:
	if (reading != switchState) {
	switchState = reading;

	if (switchState == HIGH) {
	//Send hotkey for normal (landscape) orientation
	sendKeyPress(KEY_LEFT_CTRL + KEY_LEFT_ALT, KEY_UP_ARROW);
	//Serial.println("SEND UP");
	} else {
	//Send hotkey for portrait orientation
	sendKeyPress(KEY_LEFT_CTRL + KEY_LEFT_ALT, KEY_LEFT_ARROW);
	//Serial.println("SEND LEFT");
	}
	}
	}

	// save the reading. Next time through the loop,
	// it'll be the lastSwitchState:
	lastSwitchState = reading;
	}