86 lines
4.8 KiB
Markdown
86 lines
4.8 KiB
Markdown
---
|
|
title: Arduino Uno as HID keyboard
|
|
date: 2016-07-05
|
|
author: pesceWanda
|
|
layout: post
|
|
categories:
|
|
- PesceWanda
|
|
tags:
|
|
- Arduino
|
|
- HID arduino
|
|
- mechanical keyboard
|
|
- programming
|
|
- arduino uno
|
|
---
|
|
|
|
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.
|
|
|
|
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](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.
|
|
|
|
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 But the other resources are really outdated so I hope this piece can be useful to someone out there.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have used today are on [my repos](http://francescomecca.eu:3000/pesceWanda/arduino_HID_keyboard) and I included also an outdated version of the USB Host Shield library that I used.
|
|
|
|
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.
|
|
|
|
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](http://www.freebsddiary.org/APC/usb_hid_usages.php).
|
|
|
|
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/Arduino_UNO_Keyboard_HID_version_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](https://www.youtube.com/watch?v=E8XyRwXQr8Q) 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.
|