Hack and / - Wiimote Control
If you think about it, there are almost as many ways to interface with your computer as there are Debian-based distributions—and that's a lot. Besides the trusty keyboard and optical mouse, there are trackpoint mice, touchpads, touchscreens, twiddlers, joysticks, presentation remotes and even devices that measure your brain waves. Although I mostly stick with my tried-and-true keyboard and trackpoint mouse (fingers on home row, thank you), when I started hearing about all the interesting things people were doing with the Wiimote (the main controller from the Nintendo Wii), I knew I had to give it a try.
Now traditionally, connecting a brand-new device to a Linux machine was an investment in Internet research, kernel module hacking, prayer and obscure programming skills I haven't used since college. I figured the mere fact that this was a Bluetooth device meant I was going to have to spend some quality time with hcidump. To my surprise, all the hard work already had been done for me, and I could connect and use a Wiimote on my laptop with only a few basic steps.
First, your kernel needs the uinput module available and loaded. This module is available in modern kernels, and my Ubuntu Gutsy install already had it. If you want to be able to connect to the Wiimote as a regular user, however, you need to add a new udev rule to extend permissions to the uinput device. I created a file called /etc/udev/rules.d/95-uinput.rules that contained the following:
Then, I made sure my user was a member of the plugdev group. If your system doesn't have a plugdev group, you could choose or create another group to use for this device. Next, run /etc/init.d/udev reload to make sure your changes are seen. Finally, I ran modprobe uinput to make sure the module was loaded, and I also added uinput to /etc/modules to make sure it was loaded at boot.
The next step is to install the wminput software. For me, this was simple, as wminput is packaged for my distribution; otherwise, you can download the source from the official site (www.cwiid.org). Then, make sure the Bluetooth device in your computer is enabled. For my laptop, I had to flip a switch on the side, but if you have an external USB Bluetooth adapter, for instance, now is a good time to plug it in. Finally, run wminput in a console and follow the directions:
greenfly@minimus:~$ wminput Put Wiimote in discoverable mode now (press 1+2)... Ready.
When you press buttons 1 and 2 on your Wiimote, it goes into discoverable mode, and the blue LEDs along the bottom start blinking. Sometimes you might not start discoverable mode fast enough, or wminput won't detect it, but as long as the LEDs on the Wiimote are blinking, it is still in that mode. So if wminput times out, just run the program again.
If you continually can't connect, you probably should double-check that your Bluetooth device is working. To do this, press buttons 1 and 2 on the Wiimote and then use hcitool to scan for the Wiimote. A successful scan will look like the following:
greenfly@minimus:~$ hcitool scan Scanning ... 00:1B:7A:3E:8C:54 Nintendo RVL-CNT-01
After wminput connects, you also can look in /var/log/dmesg for confirmation that the Wiimote is connected:
[ 1226.247203] usb 3-2: new full speed USB device using ↪uhci_hcd and address 13 [ 1226.288768] usb 3-2: configuration #1 chosen ↪from 1 choice [ 1227.922403] input: Nintendo Wiimote as ↪/devices/virtual/input/input21
Once the Wiimote is connected, the default bindings use it as a mouse. The accelerometers in the Wiimote are used to move the mouse pointer, so if you point the Wiimote down or up, the mouse will move down or up, respectively, and if you roll the Wiimote to the left or right, the mouse will move left or right, respectively. If you look at /etc/cwiid/wminput/buttons, you can see the default mappings:
Wiimote.A = BTN_LEFT Wiimote.B = BTN_RIGHT Wiimote.Up = KEY_UP Wiimote.Down = KEY_DOWN Wiimote.Left = KEY_LEFT Wiimote.Right = KEY_RIGHT Wiimote.Minus = KEY_BACK Wiimote.Plus = KEY_FORWARD Wiimote.Home = KEY_HOME Wiimote.1 = KEY_PROG1 Wiimote.2 = KEY_PROG2 ...
By default, wminput reads the configuration listed in /etc/cwiid/wminput/default to get its mappings. In this file you will see:
#acc_ptr include buttons Plugin.acc.X = REL_X Plugin.acc.Y = REL_Y
Essentially, this file includes the buttons file for keybindings, and it also enables the use of the accelerometers for X and Y movements. The great thing about wminput is that all these mappings are completely configurable. If you look in /etc/cwiid/wminput, you should see a number of other example mappings you can use as inspiration. You also can store custom mappings in your home directory under ~/.cwiid/wminput. The button mappings use standard names for keys and mouse buttons that can be found in /usr/include/linux/input.h, but most of the names are pretty straightforward.
Kyle Rankin is a VP of engineering operations at Final, Inc., the author of a number of books including DevOps Troubleshooting and The Official Ubuntu Server Book, and is a columnist for Linux Journal. Follow him @kylerankin.
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One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
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