Arduino Uno R3 as HID

2014-08-26T09:24:05Z

Gaess: /* Usage */

= Overview =
To change your Arduino UNO R3 into a usb HID device - for example a USB-keyboard - you will have to load a new firmware on the ATMEGA 16U2 chip on your Arduino board. That is the small square chip just behind the USB port on the board. This procedure is called DFU-programming or updating the firmware.

= Updating the ATMEGA 16U2 =
First step is to reflash the ATMEGA 16U2 so we know that our setting is actually working.
This instructions are based on some useful sites and forum hints on the web:
* [http://arduino.cc/en/Hacking/DFUProgramming8U2 Updating the Atmega8U2 and 16U2 on an Uno or Mega2560 using DFU]
* [http://forum.arduino.cc/index.php?topic=171376.0;wap2 Arduino-forum: Using Uno R3 on Linux?]
And some more hints in different forums I cannot recall anymore.

== Install dfu-programmer ==
Download dfu-programmer from your distribution repos. For Ubuntu and Debian:
sudo apt-get install dfu-programmer

Once installed, check the version with
dfu-programmer --version

It has to be at least 0.6.1 for the following steps to work. If it's not, download the programmer directly from the authors:
[https://github.com/dfu-programmer/dfu-programmer/wiki DFU-Programmer at GitHub]

== Reset 16U2 ==
The Arduino Uno R3 (I'll call it just R3 from now on) comes with pin headers for the 16U2. To reset the chip, connect the two pins closest to the usb-port.

== Flash Arduino's standard firmware to ATMEGA 16U2 ==
The following instructions are for linux OS's.

Download the latest firmware from [https://github.com/arduino/Arduino/blob/master/hardware/arduino/firmwares/atmegaxxu2/ GitHub]. The file is called
[https://github.com/arduino/Arduino/blob/master/hardware/arduino/firmwares/atmegaxxu2/Arduino-COMBINED-dfu-usbserial-atmega16u2-Uno-Rev3.hex Arduino-COMBINED-dfu-usbserial-atmega16u2-Uno-Rev3.hex] at the time of writing. You will have to open the file on GitHub as raw and save it locally with your browsers' "save" function. If the hex is stored in a wrong format locally, the flashing will fail with the error message: "Error parsing the line."

Open a terminal and change to your download directory.

Check if the programmer sees the 16U2:
sudo dfu-programmer atmega16u2 dump

You should get a gazillion of question marks on the terminal as a response.

Erase the chip, upload firmware and reset:
sudo dfu-programmer atmega16u2 erase
sudo dfu-programmer atmega16u2 flash --suppress-bootloader-mem Arduino-COMBINED-dfu-usbserial-atmega16u2-Uno-Rev3.hex
sudo dfu-programmer atmega16u2 reset

Unplug your Arduino and plug it back in. It should behave like an ordinary R3. Try uploading a sketch from the Arduino environment to check.

== Flashing HID firmware to the 16U2 ==
We're going to change the arduino into a HID device now. The code we are using is from the [http://www.fourwalledcubicle.com/LUFA.php LUFA project] and [http://hunt.net.nz/users/darran/ hunt.net.nz], who used this library to create some ready made arduino firmwares.

=== Arduino as a USB-Keyboard ===
==== Loading the firmware ====
Download the keyboard firmware and supporting files from [http://hunt.net.nz/users/darran/weblog/b3029/Arduino_UNO_Keyboard_HID_version_03.html here].

First, load the example sketch "kbd_usb_demo" on the Arduino.

Open a terminal, change to the directory where the downloaded files are and flash the firmware to the Arduino:

* Reset 16U2 (explained above)
* flash the chip:
sudo dfu-programmer atmega16u2 erase
sudo dfu-programmer atmega16u2 flash Arduino-keyboard-0.3.hex
sudo dfu-programmer atmega16u2 reset

Unplug the arduino. Open a text editor. Attach the arduino while having your text editor in focus. The Arduino should now write "hello world" and set the volume.

==== Usage ====
Some of the explanations from [http://hunt.net.nz/users/darran/weblog/faf5e/Arduino_UNO_Keyboard_HID_part_2.html here] and some own insights from the example code provided in [http://hunt.net.nz/users/darran/weblog/b3029/attachments/2d281/kbd_usb_demo.pde kbd_usb_demo.pde].

Define all modifier keys in your sketch:
#define KEY_LEFT_CTRL 0x01
#define KEY_LEFT_SHIFT 0x02
#define KEY_LEFT_ALT 0x04
#define KEY_LEFT_GUI 0x08
#define KEY_RIGHT_CTRL 0x10
#define KEY_RIGHT_SHIFT 0x20
#define KEY_RIGHT_ALT 0x40
#define KEY_RIGHT_GUI 0x80

Define some special keys in your sketch:
#define KEY_RIGHT_ARROW 0x4F
#define KEY_LEFT_ARROW 0x50
#define KEY_DOWN_ARROW 0x51
#define KEY_UP_ARROW 0x52
#define KEY_F1 0x3A
#define KEY_F2 0x3B
#define KEY_F3 0x3C
#define KEY_F4 0x3D
#define KEY_F5 0x3E
#define KEY_F6 0x3F
#define KEY_F7 0x40
#define KEY_F8 0x41
#define KEY_F9 0x42
#define KEY_F10 0x43
#define KEY_F11 0x44
#define KEY_F12 0x45

Send Alt + F1:
<nowiki>
uint8_t codebuffer[8] = { 0 }; // Keyboard keycodes buffer
void setup() {
Serial.begin(9600);
delay(200);
}

void loop() {
delay(5000);
buf[0] = KEY_LEFT_ALT;
buf[2] = KEY_F1;

Serial.write(buf, 8); // Send keypress
buf[0] = 0;
buf[2] = 0;
Serial.write(buf, 8); // Release key
}</nowiki>

Find all keycodes in Chapter 10: "Keyboard/Keypad Page (0x07)" of the [http://www.usb.org/developers/devclass_docs/Hut1_11.pdf HID usage Tables] document.

== Re-programming the Arduino after it is set as HID ==
The change the sketch on your R3 again, you will have to load the standard firmware fisrt, as explained above.