73 lines
5.1 KiB
HTML
73 lines
5.1 KiB
HTML
<p>Turin is the hometown of Arduino. I have been at the <a href="http://fablabtorino.org/">fablab</a> multiple times but I had to come all the way to America to get my hands on a simple Arduino Uno.</p>
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<p>For 60$ I bought a cheap (but still good!) mechanical keyboard by Qisan, a clone of the Arduino Uno and a USB host shield.</p>
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<p>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.</p>
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<p>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.</p>
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<p>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.</p>
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<p>In particular <a href="http://hunt.net.nz/users/darran/">this blog</a> has the most precious information and the guy wrote a HID driver that allows the Uno to be seen as a HID device.</p>
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<p>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.</p>
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<p>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.</p>
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<h2 id="a-small-journey-in-the-arduino-world">A small journey in the Arduino world</h2>
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<p>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 But the other resources are really outdated so I hope this piece can be useful to someone out there.</p>
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<p>All the files I have used today are on <a href="http://francescomecca.eu:3000/pesceWanda/arduino_HID_keyboard">my repos</a> and I included also an outdated version of the USB Host Shield library that I used.</p>
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<p>The original code from this <a href="http://hunt.net.nz/users/darran/weblog/c6f35/Arduino_USB_Keyboard_Passthrough.html">blog post</a> works like a charm but just as a simple passthrough.</p>
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<p>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.</p>
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<p>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.</p>
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<p>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.</p>
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<p>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 <a href="http://www.freebsddiary.org/APC/usb_hid_usages.php">here</a>.</p>
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<p>The process of flashing the code on the Uno goes like this:</p>
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<ul>
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<li>write the looping code;</li>
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<li>push it to the Arduino using the IDE;</li>
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<li>shortcircuit the board so that it goes in DFU mode;</li>
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<li>flash the .hex HID firmware;</li>
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<li>try your code;</li>
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<li>repeat until it’s right.</li>
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</ul>
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<p><img src="/wp-content/uploads/2016/IMG_20160706_011304.jpg" alt="Everything fits in one picture" /></p>
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<h2 id="flashing-the-firmware">Flashing the firmware</h2>
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<p>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 <a href="https://www.youtube.com/watch?v=E8XyRwXQr8Q">video</a> 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:</p>
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<div class="highlighter-rouge"><pre class="highlight"><code>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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</code></pre>
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</div>
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<p>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.</p>
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<p><img src="/wp-content/uploads/2016/IMG_20160706_011143.jpg" alt="Arduino and the shield" /></p>
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<p>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.</p>
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