I just received my first Arduino (an Arduino Uno to be specific) in the mail yesterday and have been working on setting it up to look like a HID keyboard when it is plugged into the computer. I followed ant.b's topic to get started and expanded it to fit my needs. For specific steps in the process of making the Arduino appear to be an HID device, please see his post: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1285962838
When I first came up with the idea for this project, I tried to find someone who had already done what I wanted to do. I wanted to build off of someone's experiences with turning an Arduino into a keyboard but the only information I could find that was even remotely helpful was ant.b's post. I hope that someone out there finds what I have done useful for their purposes.
Here's the Arduino sketch:
by Andrew McDaniel
Copyright (c) 2010 Andrew McDaniel
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
When we send data to the keyboard driver, it has to be
scancodes, not ascii characters. Refer to the AVR keyboard
source code to obtain the scancodes.
-Modifiers (Shift, Alt, Ctrl) only modify the next character.
-When sending modifiers, the byte that is sent must be the amount
of shift (referenced in the source code) plus 0xf0.
-Only one modifier can be used at a time.
-Once a modifier is sent, it will remain on until one of two things
happen: another byte is sent, or the same modifier is pressed on
another keyboard connected to the system.
-A delay of at least 25 milliseconds is required after each byte in
order to gice the keyboard driver time to respond. A function to
take care of this might be needed.
// meaningful constants
byte SC_A = 0x04; byte SC_SPACE = 0x2c; byte MOD_SHIFT = 0xf1;
byte SC_B = 0x05; byte SC_ENTER = 0x28; byte MOD_ALT = 0xf2;
byte SC_C = 0x06; byte SC_BCKSPC = 0x2a; byte MOD_CTRL = 0xf0;
byte SC_D = 0x07; byte SC_TAB = 0x2b;
byte SC_E = 0x08; byte SC_ESCAPE = 0x29;
byte SC_F = 0x09; byte SC_ESC = 0x29;
byte SC_G = 0x0a; byte SC_RIGHT_ARROW = 0xef;
byte SC_H = 0x0b; byte SC_LEFT_ARROW = 0x50;
byte SC_I = 0x0c; byte SC_DOWN_ARROW = 0x51;
byte SC_J = 0x0d; byte SC_UP_ARROW = 0x52;
byte SC_K = 0x0e;
byte SC_L = 0x0f;
byte SC_M = 0x10;
byte SC_N = 0x11;
byte SC_O = 0x12;
byte SC_P = 0x13;
byte SC_Q = 0x14;
byte SC_R = 0x15;
byte SC_S = 0x16;
byte SC_T = 0x17;
byte SC_U = 0x18;
byte SC_V = 0x19;
byte SC_W = 0x1a;
byte SC_X = 0x1b;
byte SC_Y = 0x1c;
byte SC_Z = 0x1d;
delay(6000); // Give the keyboard driver time to boot
sendSCString("This is being sent FROM THE ");
void sendSCByte(byte byteToSend)
// This function sends single scancode bytes.
// If using this function to send MOD bytes,
// keep in mind the above notes.
void sendSCString(String stringToSend)
int lengthOfString = stringToSend.length();
for ( int i = 0; i < lengthOfString; i++)
charByte = stringToSend.charAt(i);
if(charByte >= 0x61 && charByte <= 0x7a)
sendSCByte(charByte - 0x5d);
else if(charByte >= 0x41 && charByte <= 0x5a)
sendSCByte(charByte - 0x3d);
else if(charByte == 0x20)
This code only demonstrates sending characters and strings to the computer, but it wouldn't take much to expand it to send keystrokes on button press events.
For the atmega8u2, I used the LUFA USB stack, modified the keyboard example, and started to optimize the code for use with my Arduino sketch. Here's a .zip with all of the source needed to make a hex file (using WinAVR) for the atmega8u2:https://sites.google.com/site/projectsmcd/ArduinoKeyboard.zip?attredirects=0&d=1
If you load the sketch up and then reflash the 8u2 with the keyboard.hex file, it will begin typing 6 seconds after being reset. With that being said, be sure to have notepad or something in focus on your computer so that you don't accidentally screw up a sketch.
Please keep in mind that LUFA and ant.b's code and contributions are copyright their respective owners.