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4.9 KiB
Markdown
84 lines
No EOL
4.9 KiB
Markdown
<!--
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.. title: Arduino Uno as HID keyboard
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.. slug: arduino_keyboard
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.. date: 2016-07-05
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.. tags: Arduino,HID arduino,mechanical keyboard,programming,arduino uno,PesceWanda
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.. category: PesceWanda
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.. link:
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.. description:
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.. type: text
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-->
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Turin is the hometown of Arduino. I have been at the [fablab](http://fablabtorino.org/) multiple times but I had to come all the way to America to get my hands on a simple Arduino Uno.
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For 60$ I bought a cheap (but still good!) mechanical keyboard by Qisan, a clone of the Arduino Uno and a USB host shield.
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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.
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You can imagine that given this three pieces of hardware together I put together an hardware key mapper for the keyboard.
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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.
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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.
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In particular [this blog](http://hunt.net.nz/users/darran/) has the most precious information and the guy wrote a HID driver that allows the Uno to be seen as a HID device.
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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.
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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.
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## A small journey in the Arduino world
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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.
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All the files I have used today are on [my repos](http://francescomecca.eu:3000/pesceWanda/arduino_HID_keyboard) and I included also an outdated version of the USB Host Shield library that I used.
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The original code from this [blog post](http://hunt.net.nz/users/darran/weblog/c6f35/Arduino_USB_Keyboard_Passthrough.html) works like a charm but just as a simple passthrough.
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It was not difficult at all to examine the code:
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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.
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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.
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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'.
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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.
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The modifier bit at the beginning of the array came in handy for my code.
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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.
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I got all the codes for the HID events [here](http://www.freebsddiary.org/APC/usb_hid_usages.php).
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The process of flashing the code on the Uno goes like this:
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* write the looping code;
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* push it to the Arduino using the IDE;
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* shortcircuit the board so that it goes in DFU mode;
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* flash the .hex HID firmware;
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* try your code;
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* repeat until it's right.
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## Flashing the firmware
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The firmware is in my repo but I got it from (here)[http://hunt.net.nz/users/darran/weblog/a6d52/Arduino_UNO_Keyboard_HID_version_02.html].
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The tool I used to flash it is dfu-programmer (version 0.62).
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Every time you want to flash a new firmware the Arduino must be put in DFU mode (you can see the difference with lsusb).
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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.
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This [video](https://www.youtube.com/watch?v=E8XyRwXQr8Q) shows the method briefly (no real need for a jumper).
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The commands are the following and there is no risk to brick the Uno:
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```
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dfu-programmer atmega16u2 erase
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dfu-programmer atmega16u2 flash Arduino-keyboard-0.2.hex
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dfu-programmer atmega16u2 reset
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```
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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.
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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.
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