How the Wiimote Works

The New York Times' 'How it Works' series touches on a remote with a twist: the Nintendo Wiimote. The article describes the micron-sized machines that make it work, displays cut-away graphics of the little white marvel, and rounds out the discussion with a breakdown of where the tech came from. From the article: "The controller's most-talked-about feature is the capacity to track its own relative motion. This enables players to do things like steer a car by twisting the remote in the air or moving a game character by tilting the remote down or up. 'This represents a fabulous example of the consumerization of MEMS,' the tiny devices known as micro-electro-mechanical systems, said Benedetto Vigna, general manager of the MEMS unit at STMicroelectronics, a leading maker of the accelerometers embedded in the controllers. (Nintendo itself declined to talk about the controllers' inner workings.) He said the motion sensors, using the technology that activates vehicle air bags, can accurately sense three axes of acceleration: up and down, left to right, and forward and backward."

Wait...

can accurately sense three axes of acceleration: up and down, left to right, and forward and backward.

Wait, isn't that six axes? Oh, I guess it's just Sony that likes to make shit up.

Re:Wait...

I agree, but calling it threeaxesandthreedimensions doesn't get you a snappy palindromic name.

That's why they should have called it something super-awesome like Axis of Threevil.

Little low-tech for SlashDot, eh?

How the Wiimote Works

C'mon, "editors"...this is SlashDot, not Time. Most people here could probably have written that article blindfolded. How about a couple of real tech articles today?

Re:Not troll

Time is very dumbed down, and uses slang my middle school English teacher wouldn't allow. That's for non-technical articles.

That's not very nice. I mean they named you as "Person of the Year" after all, didn't they?

Air bags? Perfect!

This just in.

Nintendo is using their wiimote technology to determine when the wiimote flies from the users hand, and will now deploy an airbag before striking your HDTV.

Please return your wiimote for the new version with the wiirbag.

only three axis?

The sixaxis must be twice as good! Either that or Sony failed geometry...

Analogies rule!!!

These accelerometers are so sensitive, Mr. Vigna said, because electrons -- those subatomic particles that whirl around the nucleus of atoms like a video game in the making -- can sense the subtle atomic-level movement of the silicon structures.

Even for /. that's a messed up analogy. How is an electron like a video game in the making? Or is it the whirling around the nucleus that resembles the video game creation process?

simplified "how it works"

I thought the Wiimote worked like this:

If you see a monster, throw the Wiimote directly at the monster. Depending on your aim, the monster will die in a shower of bright sparks and crackly noises, or the monster will hurl various objects back at you such as books, chunks of plaster, ceiling fan blades, or your little brother's eyeball.

Imagine the possibilities

independent researchers have shown that there is a strong link between very high voltages coming from the accelerometers and the state of inebriation (and perhaps low IQ) of the player...

No disassemble!!

So did they actually use tools to open the Wiimote up carefully? Or did they fling it with all their strength at an HDTV to get both an article, and piece of the class-action? [slashdot.org]

Didn't Live Up To The Hype

After having used my Wii and the controller for a couple weeks now I've been somewhat disappointed with the technology.

First, the Wiimote isn't an absolute pointing device. It's all relative to the Wiimote bar you place near your TV. Everything is relative to that device, so you are never actually pointing accurately at anything on your screen.

Second, the Wiimote has accuracy/responsiveness issues. Not sure if it is interference from bright lights or some other type of wireless/electronic devices. There are times where you are having to repeat the same motions over again because the Wiimote isn't registering.

Nothing fatal, but the hype certainly has worn off. Hopefully Nintendo will be coming out with updates to make the Wiimote more consistent in registering input over the next year.

Re:Didn't Live Up To The Hype

It's all relative to the Wiimote bar you place near your TV. Everything is relative to that device, so you are never actually pointing accurately at anything on your screen.

That's because the bar provides the infared source so the Wiimote has a frame of reference for the TV screen. Since it provides the infared source, anything that may alter the source will interfere with the Wiimote (i.e.: shiny surfaces like a coffee table, glass, mirrors, etc.). Of course, it is also why you can substitute the bar for 2 candles [wiihaveaproblem.com].

Re:Not informative

Why would you want to have to calibrate it for the TV? The way it is set up right now, it is all relative. It doesn't have to aim exactly where you are pointing, it just has to change its position based on your movements in a consistent manner. The way it is now, i can go from a 23 inch TV to a 9 foot wide projector image with absolutely no calibration. Plug it in and go. That's really special.

Re:Didn't Live Up To The Hype

If your wiimote is a little off make sure you check the sensitivity to calibrate it.
I found that made a huge difference.

Re:Didn't Live Up To The Hype

First, the Wiimote isn't an absolute pointing device. It's all relative to the Wiimote bar you place near your TV. Everything is relative to that device, so you are never actually pointing accurately at anything on your screen.

I don't think it ever was lauded or presented as an absolute pointing device prior to its release, but it is a very good ubiquitous pointing device and not simply a one trick pony as something like the Zapper was. As stated by others before me, this is because the sensor bar emits the IR which the wii-mote triangulates its pointing position from. It definately works best on the top of the TV, IMO. Ideal setup can vary depending upon whether you are typically sitting or standing, how high your TV is relative to the ground/seat, etc. Calibrating it is important too -- in my mind, that's one of the things that killed Red Steel - you can only calibrate at the very begining of the first level and not from the pause menu while pointing is an essential part of the controls. In Zelda:TP, you can play entirely without using the pointer and it still has a more advanced calibration option than the beginning of Red Steel available at all times (if only you could turn down the tingling fairy sound).
It would not be possible to have an absolute pointer that would work on all TVs; they would have to actually sell a Wii TV (a Wii-V?) with the IR beams behind the screen to make an absolute pointer. The reason the Zapper and other light guns worked as something like an absolute pointer is because the tech was different, and as I understand it will not work on some modern TVs (I can't recall if its LCD or Plasma). When you pulled the trigger on the Zapper, the screen flashed black for a frame, and the area around the target sprites flashed white after that to indicate a target. The photo-receptors in the Zapper would detect that different to determine a hit or miss. Would you really want the screen flashing right with every shot in any modern FPS? The problem with using something like an invisible later pointer is that TV screens are not flat, and are usually convex. To do a reflective pointer you would ideally want a concave screen with the player at the focal point. By using IR and having each Wii-mote figure out its own position, you don't have to worry about different controllers interfering with each other's signals, etc.

Second, the Wiimote has accuracy/responsiveness issues. Not sure if it is interference from bright lights or some other type of wireless/electronic devices. There are times where you are having to repeat the same motions over again because the Wiimote isn't registering.

If you're having accuracy/responsiveness issues with the pointer, your most likely culprits are 1) other bright lights (including sunlight) in your gaming area 2) Other heat sources that aren't lights in the gaming area (i.e. laptop with running harddrive on the coffee table) 3) possibly reflective surfaces, but doubtful. If you aim your Wii-mote away from the screen and happen to pass another heat source like a candle or laptop, it may temporarily focus on that for triangulation, causing all sorts of problems, so keep your gaming area free of IR sources that can distract the remote. Lights should only be a problem if they are also a significant heat source (incandescent bulbs), and darkened rooms are better for gaming anyway.
I haven't had any obvious problems with Wi-Fi, but it and Bluetooth do operate in the same range, as do most cordless phones. If you're having response problems regularly, try changing the set channels on your Wireless router and/or cordless phones.
As for response issues with other motions, I have occasionally noticed some problems (like with batting in Wii baseball), where the bat seems way off, but if you go back to a base position and restart your motions, it usually comes out just fine. One of the tricky parts to motion recognition is determining which motions were deliberate a

And the firmware is available too..

..to the Wiimote [sparkfun.com] - at least reversed from the eeprom on the device. This should improve the compatibility of PC's to the Wiimote, and I hope we see some interesting applications on the PC soon ; that or Nintendo should release a Wii-SDK, otherwise I think they are definitely losing a whole lot of interest in the long run of the more adventurous type of user who longs for interesting applications for this simple (proven) but now widely available concept of three-axis sensing devices.

Motion or angle?

I'm a bit confused. The ability of the Wiimote to sense the angle it's at seems quite consistent, and doesn't appear to be possible to "fool", while the ability to sense motion can be fooled somewhat.

It seems to me that they must be separate, at least a little. You can walk away with a Wiimote, far out of bluetooth range, turn it however you like, bring it back... And the console will still sense its orientation precisely. Location? Games that use that sometimes get out of sync so you have to wave the Wiimote around a bit to get them better calibrated.

So I'm pretty sure that's a separate feature, to say nothing of the additional component of the CCD pointing at the IR sources above your TV to give you a pointing device.

Re:Motion or angle?

Having done some inertial engineering work, I can shed some light on this issue.

The Wii-mote has accelerometers on it. These sense forces applied to it (gravity included), and their combined output is a vector indicating the direction and modulo of the resultant acceleration. Assuming you're standing still, you'd only be subject to the force of gravity, and by definition it always points to the ground. So do a few vector computations and you know the orientation of the Wii-mote. There is a problem with a `blind axis' (rotation in the same axis as gravity can't be detected), but ignore that for now.

On the other hand, if you want to estimate position, here's what you have to do: given an initial position, read the accelerometers, subtract the effect of gravity from the acceleration vector (harder than it seems, since the Wii-mote could be pointing anywhere, really), which then gives the `real acceleration' of the system. Now integrate this once to obtain velocity, and again to obtain position. There's just so much room for error here, that I don't know where to start. Limited accelerometer resolution, poor A/D converters, temperature drift, numerical accuracy issues, you name it. Integrating measurements (not only that, but integrating twice!) is just a recipe for disaster. Then there's a fundamental limitation to accelerometer devices: rotations can't really be distinguished from translations. Just think about it -- a given resultant acceleration vector could be the result of pointing the Wii-mote in any given orientation, added to a specific acceleration in a specific direction. You just don't have enough information to distinguish between the two -- not with accelerometers alone, at least.

Hope that helps.

The one missing feature

While I love the Wiimote and Nunchuk, I think they really suffer from the lack of at least a single-axis gyroscope. The accelerometer is great for measuring tilts in relation to the earth's surface, but they can't register angles on axes perpendicular to the earth's surface. This makes it more difficult to register a camera pan to the left or right, for instance, without involving the IR sensor.

The most obvious use (to me) for such a feature would be to have the Nunchuk pan the camera left and right as you point it left and right (in FPS games for instance), but it would also improve situations like batting and swordfighting where you want the instrument onscreen to match the angle of the Wiimote as closely as possible.

What?

He said the motion sensors, using the technology that activates vehicle air bags

This is fucking hilarious. I will proceed to let you know precisely how most vehicle air bags are activated.

It is true that in the more modern vehicles there is ONE accelerometer per direction of air bag. This is used to set off air bags other than the front. There is usually one accelerometer to set off the front air bag.

HOWEVER this is not the only input. In fact it takes two inputs to set off the air bag. One input is that accelerometer sensor. The other input is either crash sensor mounted in or near the front bumper.

This is the hilarious part - these sensors typically consist of a magnet, a ball bearing, a ramp, and a set of contacts with another magnet. A sufficient shock will break the ball bearing free of the magnet, at which point it rolls up the ramp (again, if the shock is enough) and sticks to the other magnet, closing the switch contacts.

So what this guy is saying is that the technology in the Wiimote utilizes is a combination of an accelerometer and a ball bearing rolling up a ramp.

Seatbelt? High-tech shit! --Carlin

Re:I heard...

Yeah, cause when you become an immortal cyborg you're going to want to take your wii with you as you travel into the inter-galactic void.

Re:I heard...

Assuming ten thousands oscillations a second, that's a life span of 3171 years or so. A million oscillations a second gives 31 years. I'm pretty sure it doesn't need to oscillate any much faster then a few kHz though...