The AlpineInker : OQO Model 02, Tablet PC

The Microsoft Research Codex: Are Dual Screens the Future of Mobile Devices?

Ken Hinckley — Wed, 01 Oct 2008 10:17:00 GMT

Never buy one of anything. That's advice you should stand by when you're buying unusual gadgets. The advice was good when Randy Pausch offered it to me some 15 years ago, and it's still good now.

Of course, with 18 month old twin girls at home, this has become second nature to me. Two boxes of diapers. Two gallons of milk. Two Elmo plush dolls.

Oh, and yes, of course. Two screens for my tablet computer.

Dual-screen devices have become the subject of increasingly elaborate internet fantasies. Now, rumors about an Apple "Brick" device have stirred up dreams of future tablets, such as the alluring One Laptop Per Child v2.0 concept photos, which now orbit the internet once again.

My interest in dual-screen devices goes back a lot further, though, and was really spurred on by the University of Maryland dual-screen e-book reader project. That effort is led by Francois Guimbretiere, who is a long time collaborator and friend. I had some ideas to build on what his team had done, but also to take things in a different direction.

First of all, I wasn't interested in an ebook reader. I wanted a device that was all about writing. Sure, reading and writing go hand in hand - you encounter cool ideas and search out reference material on the web-but what I wanted to build was a tool for thought. To me that means a tool with writing, sketching, and annotating as the core of the experience.

I'd been thinking for a long time about picking up an OQO Model 02 computer. My team has an extensive code base for pen-and-tablet functionality resulting from InkSeine, and the OQO runs it out of the box. It's got an active digitizer for high fidelity pen input, and it's the smallest slate Tablet PC that money can buy. That's a pretty good start on a small form-factor tool for thought.

So when it came down to it, just how many of those OQO Model 02's do you think I purchased?

Project "Codex" was born.

Twice the Screen at Half the Size

Here's the Codex packed up for mobility. It folds up quite nicely and has a moleskine-style knitted elastic strap to hold it securely shut. There's a loop for the pen and a mesh pocket so you won't lose small accessories, business cards, or receipts that you collect in your travels.

Sure, it's a bit of a brick at present. The whole thing weighs just over 2 pounds. The OQO's are considerably thicker than I'd like. But my goal is to prototype the future as quickly as possible and start living it. The OQO offers a handsome, jet black time-travel machine in that regard.

Don't underestimate the ability to quickly pack up with the screens protected. Folding the Codex in half makes it comfortable to carry and easier to stuff into my gadget bag. It's a self contained kit for ultra-mobility.

The Codex is Not a Container for Dead Trees

A codex is just an archaic term for a bound book. But this Codex is unlike any book that you've ever read. It's not a long linear text that you flip through. To me, there's no use in going to all the trouble to build a dual-screen tablet prototype and write elaborate software just to mimic a traditional book. This is the 21^st century and it's about time we moved past containers for dead trees.

We have lots of information sources. We have multi-tasking. We have hyperlinks. We have split attention. We have a left brain and a right brain and we rarely do one thing at a time any more.

A Separation of Concerns

The Codex has two screens, it's designed to be used that way, and you won't find any half-apologetic demos that try to mash them back together into one big screen. Instead, it's all about the intelligent partitioning of tasks and interface elements across the screens.

Above is one example where I'm working on a blog post that I've had planned for a while. On the left I have a whole bunch of cool photos that I found tagged with moleskine on Flickr. I was browsing through these as inspiration for our InkSeine digital note-taking software. On the right I'm organizing bits and pieces from these photos along various themes. So I just take a snapshot from the collection on the left screen and it appears in my notes on the right screen, where I can arrange it and mark it up as I see fit. I can scroll back and forth on the left screen to find a photo that meets my current needs, while the page that I am authoring on the right screen always remains visible. The two screens are invaluable because I always have the reference material in the context of what I am working on, instead of feverishly flipping between them on a single screen.

Can I do this on a single large screen? Well, sure, I could monkey with the window placements and get everything arranged just so. But that takes a lot of effort and the temptation to expand windows to take over the full screen is hard to resist if I have to expend effort to do so. A dual-screen device that understands the partition between the screens gives a much simpler experience where I don't have to constantly manage the set-up of the windows.

Navigate without Losing the Big Picture

Here's another example. I'm further along with authoring my blog post now, and I have a bunch of material floating around in my notes. I create a page that is a Table of Contents, with links to several themes that I've identified in my Flickr moleskine investigations. If I open a link, such as my Creative Collage page, it opens on the opposite page. I don't even need a "back" command to return to where I was - I still have my navigational structure on the left, side-by-side with my content page on the right.

Unlike a traditional dead-tree book, I have no physical restriction that forces me to view consecutive pages - The Codex lets me follow links or flip through the screens separately to view any two pages together.

Working Big and Small

We can draw some inspiration from traditional media as well. In magazines and books, sidebars are a distinct section of a page that augments the main text with auxiliary information. Well, the Codex has sidebars on steroids. I can take any chunk of my notes, make it into a sidebar, and then arrange a bunch of these on a page. Here, I've made a storyboard page consisting of six sidebars. When I tap on a sidebar in one of the storyboard cells, it expands to full size on the opposite screen. I can plot out the broad sweep of my story on one screen, while maintaining full access to the zoomed-in details on the other.

Your Mother Was Right - Posture is Important!

Perhaps the coolest property of a dual-screen device is that the compact, mobile form-factor encourages shifting the device around. I can orient the screens with respect to one another, stand the device up, look at the screens in portrait or landscape, and so forth. In fact, the Codex supports about a dozen different configurations. We call these postures. (A colleague, Michael Miller, coined this term).

Add two cups of accelerometers, a dash of flex sensors, and bake with some simple software to fuse it all together. Out of the oven pops an intelligent dual-screen display system that configures itself depending on how you arrange it.

For example, if I want to work in landscape, I can flip the device into the laptop posture, as opposed to the book posture that I've been showing so far. Now I have one screen that's angled for easy reading, plus another screen that's horizontal for easy writing.

Or I can use the laptop posture to hook up one of my screens to a projector. I put the public part of my presentation on the top screen, while the controls to drive the presentation and my private notes are confined to the bottom screen.

Now perhaps I meet a friend in a café and I want to show him what I'm up to. I can just lift up on the binding of the Codex to angle the screens so that one is facing me and one is facing my friend (below, left). We call this the battleship posture - as in "You sank my Battleship!" Each person has one screen with a private view. The Codex automatically configures the software for shared whiteboarding so the collaborators can mark up the screens, pass notes back and forth, and other such foolishness.

Next I drop the binding back flat. Now both of us can view the screens, but one screen is oriented towards each person.

Don't Get Too Attached

Something that turned out to be surprisingly useful is that the Codex allows me to pull each screen right out of the binding. A firm pull pops it out, a firm press pops it back in. This is really handy for laying out the screens to suit my work, or to review a video while I jot down some notes. I can even hand the screen to another person to show them something - without actually giving them an electronic copy of the information.

What? You Still Have a Desktop Computer?!?

The Codex is just another wireless device so of course I can connect it to my desktop computer. Now, any screen capture that I take from my desktop screen shows up in my Codex notes right where I left off. For web pages, the snapshot comes across with a hyperlink back to the source, so I can easily revisit it later when I'm reviewing my notes on my Codex. This makes it the perfect companion no matter how I'm working.

A Parting Shot at Text Entry

The Codex is designed around doing most things with a pen, but I'm no idiot. When it comes to text entry, a keyboard is a good thing.

And that, in part, is why I'm puzzled that so many of the dual-display concept designs that I've seen take up a whole screen with a virtual keyboard. I'm sure people in focus groups ask for this. But I still think it's a really bad idea. What is the point of having two screens if you are instantly going to cover one of them with a picture of a keyboard? Your hands immediately occlude it from sight anyway. At that point I'm basically using a single screen again, so I might as well just grab my laptop to get a decent keyboard.

The Codex offers a solution for text entry that I much prefer, by virtue of the OQO Model 02's mechanical keyboard. I just slide the screen up and that reveals the keyboard when I need it. Works great. No dorky touchscreen keyboard. I still enjoy the full benefits of partitioning my work between the two screens. That's the way I like it.

When Can I Buy One?

The Codex is a prototype-- and a rather flaky, cobbled-together one at that. But it uses off-the-shelf devices, and there's nothing magical about the software. So the crass answer is that you can have one now if you are willing to spend some dollars, build yourself a custom binder, and write a little bit of code. That's how I started. My first prototype was a repurposed day-planner with Velcro holding the screens in there. Install a shared clipboard utility and you can start copying and pasting between screens. That will give you just enough of the experience that you will hunger for more.

What would you want out of a dual-screen device? What capabilities would make it most useful to you? How do you see dividing your own work between two screens?

In the meantime, the trajectory of ultra low-power "e-ink" displays bears watching. Check out the recent Plastic Logic device, for example. Right now e-ink is an abomination for anything interactive, but eventually some display technology will get where we want it to go. Low-cost, low-power screens are crucial to make dual display devices a practical consumer device, rather than a research lab curiosity.

The sheer number of concept devices that have popped up in the last 6 months suggests that dual-screen devices are poised to take off in the near future. My hope is that our research on the Codex can help in some small way to unearth the full promise of such devices. I, for one, am convinced that dual-display devices have a well-motivated role to play in a future ecosystem of mobile devices.

In my office, at least, that future is already here. It's just not evenly distributed.

Acknowledgements

I would like to thank the following key contributors to this project:

Morgan Dixon
Raman Sarin
Francois Guimbretiere
Ravin Balakrishnan

Some Thoughts on Automatic Screen Rotation

Ken Hinckley — Thu, 08 May 2008 08:41:00 GMT

Automatic screen rotation has been popularized by the iPhone but is also available on the OQO Model 02 thanks to Kenrick's Automatic Screen Rotator Utility (executable download). Just hold the device the way you want to use it. The screen flips to the correct portrait or landscape orientation in one second. You don't even have to think about it. What could be simpler? Kudos to Kenrick for putting this great utility together and making it available for free!

This is a program near and dear to my heart. I cobbled together custom sensor hardware, including an accelerometer to support automatic screen rotation, for my old Cassiopeia E105 Pocket PC back in the late 1990's:

Here's our video of the Sensing Pocket PC, with screen rotation and other fun stuff too.

Video: Sensing Techniques for Mobile Interaction

Later, I built sensors for the original slate Tablet PC prototypes that were floating around Microsoft. Many devices now include accelerometers for drop detection, but I'm pretty sure my prototype was the world's first Tablet PC with an accelerometer. It came with an extensive user manual: TILT ME.

That wad of electronics on the top is my sensor module. Here, I'm using the Tilt-a-Sketch application. You could draw on the tablet like an Etch-a-sketch by tilting it back and forth. Yes, it was really hard to sign your name this way, and yes, if you flipped it upside down and shook it, it erased the screen. Accelerometers can be a lot of fun.

But what was the most useful? Like Kenrick's utility, it supported automatic portrait/landscape switching depending on how you held the device. After all that hard work I had to put into building my own sensors, firmware, and software, it's mind-blowing to see this available in a free utility that I can download from the 'net for an off-the-shelf device!

My demo had a few tweaks, some never published before, that might be useful future embellishments to Kenrick's Automatic Screen Rotation utility. In essence these tweaks reduce accidental changes to the display orientation when you're working with your device. They also help to avoid rotation of the screen when you go to set your device down on your desk. Plus there's one bonus idea I tinkered with, described at the end - let me know if you like it or not.

Dead Bands for Increased Stability

Dead bands between the screen orientations made the device tend to stick to the current display orientation. This helped to avoid accidental changes to orientation.

Plot of tilt angles versus inferred instantaneous screen orientation.

To change display orientation, the tilt angles had to pass all the way through the gray ±5° dead bands, and stay within the same display region for 0.5 seconds. No screen rotation occured in the central "Flat" area.

Rotation Preview

Feedback for impending display rotations makes automatic changes to the display orientation more predictable and controllable. My Tablet PC demo displayed a "THIS SIDE UP" arrow at the center of the screen as soon as the tablet was tilted in a different direction. The change to the display format occurred one second after the arrow appeared, but only if the device was still tilted towards the new display orientation. This allowed the user to stop tilting the device to prevent an inadvertent switch.

To foreshadow a change to the display orientation, an arrow appeared immediately when the user rotated the tablet.

Of course, the arrow should not be there all the time. The arrow vanished when:

The screen changed orientation. The arrow remained visible for a couple of seconds after the switch to provide continuing feedback.
The instantaneous screen orientation returned to the current display orientation for a couple of seconds. This case occured if a user acted on the feedback to avoid an accidental change.
The user set the Tablet down flat without changing screen orientation.

I used black color-key transparency (in a layered window) for the actual bitmap used in the code.

Motion Detection

Movement of the device serves as a secondary indicator of when to switch the display format. To avoid accidental changes to the screen orientation, my Tablet PC implementation waited for motion to stop before rotating the screen. For example, this made the device less likely to change screen orientations as you set it flat on a desk.

The OQO Model 02 supports only about a 4 Hz sampling frequency on the accelerometer, so it might not be feasible to implement good motion detection at present. Nonetheless it seems worthwhile to mention it, in the hope that an increased sampling rate becomes possible in the future.

One hack to detect motion is to calculate how much the tilt values are changing, as follows:

Δx = tiltX - prevTiltX

Δy = tiltY - prevTiltY

sampleEnergy = √(Δx² + Δy²)

signalEnergy = signalEnergy*(1-α) + sampleEnergy

In the final equation, α is a decay rate. I used 0.25, with the tilt values in degrees, and signalEnergy initialized to 1.0. Motion "begins" when the signal energy rises above an onset threshold for a few samples and "stops" when the signal energy drops below a termination threshold.

Movement helped to control switching of the display format as follows:

When movement stopped, if the physical screen orientation did not match the inferred instantaneous screen orientation, a 1 second time-out began, after which the software switched the physical display orientation.
If movement began again during this time-out, the time-out for the physical display switch was cancelled.
If the instantaneous screen orientation changed again during this time-out, the time-out was restarted at its full one-second duration.

Orientation-specific Tasks

Here's one other nutty idea I experiemented with. Maybe it's useful, maybe it's not.

I assigned specific applications to specific orientations of the screen. For example, here's a screen shot where I set up Excel to appear in the landscape format, and Windows Journal in the portrait format. Flipping my Tablet PC between the two would switch between the applications, rather than just rotating the screen.

Switching orienations can switch between sets of applications as well...

This offered a simple way to partition applications into task-specific sets for each screen orientation. Unfortunately my prototype of this feature never really worked all that well. You could check off windows as belonging to each screen orientation. The prototype would hide and show the windows as you rotated your tablet. But it had some bugs. Sometimes it would hide the windows permanently, never to be seen again. That's not terribly useful. So I never did usability testing on it, but I found something about it intuitively appealing. What do you think? Would you want this feature on your tablet or mobile devices?

Summary

My experience is that the devil is in the details with sensing techniques. Small touches here and there go a long way to keep the interaction invisible in the background, rather than becoming a focus of attention when things happen that the user didn't intend. Ultimately, the goal should be to create the best possible user interface. What is the best possible interface, you might ask?

The best possible user interface is the one that you don't even notice is there at all.

Resources:

Kenrick's blog: Teaching, Technology, and Learning
Kenricks' Automatic Screen Rotator Utility, download for the OQO Model 02
Ken Hinckley's UIST 2000 conference paper and follow-up journal article on sensing techniques.
Video of the Sensing Pocket PC

My New Favorite Flick Pad

Ken Hinckley — Tue, 29 Apr 2008 19:30:00 GMT

I just received an OQO-style moleskine in the mail!

When I opened it up, it was full of arcane tricks for using InkSeine's Tool Ring as a flick pad. This topic has come up before but now it seems that perfect combination of custom flicks has been discovered.

This is the new set of Flick gestures that I've adopted for the OQO. Show Desktop is especially handy!

Right flick mapped to Alt-Tab - great for flipping between two windows. This one you need to manually configure by choosing the (add) option from the drop down.
Down flick mapped to "Toggle Ctrl" which is one of the standard choices in the drop-down. I use Ctrl with the ToolRing's scroller to zoom.
Diagonal-upper-left flick mapped to Right Click. Also a custom combo, just hit the right-click soft key on your TIP to add this one. (It shows up as "Application" when you press it).
Up flick mapped to Show Desktop - my absolute favorite! A quick flick up on the Tool Ring always gets me to my desktop, which is a handy place to stash all your shortcuts on a tablet. This is also a custom combo consisting of "Windows + D", where Windows is the Windows logo key.

Here are my notes... flick up to Show Desktop:

Voila! There it is! But even better... doing Show Desktop again... puts me right back where I was!

I'm also debating whether I want to replace Undo with Enter instead. It's handy for opening selected files without double-tapping. I guess I'll have to see. But I'm keeping Copy, Paste, and Back for sure - unless I find something better the next time I flip back to this idea!

Here's the return address label on the back cover. I have no idea who this is. And it's been a long time since two cents cut it for postage. It's all a bit mysterious. But whoever you are, keep the tips coming!

Posts in the Tool Ring Shenanigans series: