+ + Arduino Uno as HID keyboard + +
+ + 05 Jul 2016 + +Turin is the hometown of Arduino. I have been at the fablab multiple times but I am more of a software guy. +I had to come all the way to America to get my hands on a simple Arduino Uno. +For 60$ I bought a cheap (but still good!) mechanical keyboard by Qisan, a clone of the Arduino Uno and a USB host shield.
+ +Given that is 3 years since I have been using a dvorak layout and it's a pain to change layout on every machine that you have to use. +You can imagine that given this three pieces of hardware together I put together an hardware key mapper for the keyboard.
+ +I have never had experience with Arduino before but it was not that difficult to make it do simple things like blinking the led or send signal through to a serial monitor.
+ +It took me half an hour to wear down all my excitement: the USB Host Shield library broke all the compatibility with the similar project I found wandering online.
+ +In particular this blog has the most precious information and the guy wrote a HID driver that allows the Uno to be seen as a HID device.
+ +It was a noob error but I didn't checked the various arduino alternatives and I discovered late that just a few have the HID capabilities that would make this work easier. I should have bought and Arduino Due or Leonardo maybe.
+ +Also, the various guides about flashing with a dfu tool are specific to older models of the Uno and it took me some time to figure the name of the new components so that I could flash a new firmware.
+ +A small journey in the Arduino world
+ +It feels pretentious to write a little guide for this kind of work, given also the fact that I have roughly 10 hours of experience with the Arduino. But the other resources are really outdated so I hope this piece can be useful to someone out there.
+ +All the files I have used today are on my repos and I included also an outdated version of the USB Host Shield library that I used.
+ +The original code from this blog post works like a charm but just as a simple passthrough.
+ +It was not difficult at all to examine the code: +during each loop of the iteration a char array gets read from the shield and if it is contains information Arduino with the Serial.Write method send the data to the host.
+ +The buffer array is a simple array of length 8 and the first two positions are reserved. In particular the first one represent the various modifier keys.
+ +The dvorak layout has the same pairs as the US layout but eventually I got used to having the '@' where at the same place of 'Q' (qwerty) and '"' over the '2'. +Also, I am an avid ViM user (I should thank Simone Basso for that) and I swapped some keys on the new 65 keys keyboard. +The modifier bit at the beginning of the array came in handy for my code.
+ +An hardware key remapper is a simple but long switch C statement but I decided to consider also the modifier bit: in this way certain keys like the Window (UGH!) key is mapped to a different layer of keys. +I got all the codes for the HID events here.
+ +The process of flashing the code on the Uno goes like this:
+ +-
+
- write the looping code; +
- push it to the Arduino using the IDE; +
- shortcircuit the board so that it goes in DFU mode; +
- flash the .hex HID firmware; +
- try your code; +
- repeat until it's right. +
Flashing the firmware
+ +The firmware is in my repo but I got it from (here)[http://hunt.net.nz/users/darran/weblog/a6d52/ArduinoUNOKeyboardHIDversion_02.html]. +The tool I used to flash it is dfu-programmer (version 0.62). +Every time you want to flash a new firmware the Arduino must be put in DFU mode (you can see the difference with lsusb). +To do that simply create a shortcircuit using a small metal wire on the two pins near the reset button and a led will blink. +This video shows the method briefly (no real need for a jumper). +The commands are the following and there is no risk to brick the Uno:
+dfu-programmer atmega16u2 erase
+dfu-programmer atmega16u2 flash Arduino-keyboard-0.2.hex
+dfu-programmer atmega16u2 reset
+
+After each flashing the device needs to be disconnected once. Of course you can flash the original firmware back. It is included in my repo or on the official ones.
+ +
That's it, as you can see is not difficult at all. The worst part is gathering the various info that are left dormant in blogs or forums.
+ +
Fine's
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