Break It Down – How Does The S Pen Work?

February 6, 2013
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Who knows what we’ll see unveiled at Mobile World Congress, but with its recent purchase of five percent of Wacom, Samsung has shown that it believes there is a future in the S Pen.

And why not? It’s a nifty piece of hardware that allows users to do some very interesting things. The popularity of the Samsung Galaxy Note 2 isn’t entirely thanks to the S Pen—a long way from it, actually—but it certainly didn’t suffer because of it either.

Whether you like to use it or not, you may find yourself wondering how the S Pen works. Well that’s what we’re here for.

If you’re in a hurry, check out the three sentence summary, or watch the video.

Where Does The Power Come From?

You might have wondered this already. The S Pen has a button that obviously communicates with whatever Galaxy Note device you’re using, so it has got to require some power, right? One possible solution would be a rechargeable battery that would charge when the S Pen was stowed away, but this isn’t the case. So where does that power come from?

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The answer: the S Pen pulls the power wirelessly from the device. See, behind the screen is a circuit board, a grid of coils, and a magnetic reflector. Together, these generate an electromagnetic field that emanates outward from the screen. How far does it go? Well, you know how when you move the S Pen close enough, the “hover” icon comes up? Right about there.

Inside the S Pen itself is another coil that channels the power from the field to its own internal circuit board. It uses this power to communicate information from its buttons back to the Note device. And no, that isn’t a type. I said buttons.

The Screen Has Nothing To Do With It

Alright, in the technical sense, maybe it isn’t a button, but that’s the easiest way to think of the tip, or “nib” of the S Pen. See, as the heading just above this paragraph says, the screen has nothing to do with writing, drawing or navigating using the S Pen.

The same electromagnetic field that provides power to the pen can also be used to calculate its position relative to the screen. This, along with information from the S Pen button and the nib on the end are what is used to determine what the user it doing with the S Pen.s-pen-3

If you have a Note device and S Pen handy, you can easily test this for yourself. Pick up the S Pen, push down the nib and move it in close to the screen. You’ll notice that you can draw in the air with the S Pen and it shows up on the screen just as it would if you were using it normally. For another test, take a business card or piece of cardboard, hold it over the screen, and if you’re close enough, you’ll be able to draw on this and see it on the screen.

What About Pressure Sensitivity?

Ah yes, pressure sensitivity. Again, as mentioned above, the screen has nothing to do with it. This is all in the S Pen. For all the levels of pressure sensitivity Samsung touts, I’ve basically only noticed two. Okay, make that three, if no pressure at all counts as a sensitivity level.

It’s interesting though: I personally found that once I knew that all the pressure sensitivity information came from the S Pen itself and not the screen, I was able to get more sensitivity out of it. Note that this still didn’t help my drawing or handwriting skills, but it is still worth pointing out.

Why Don’t More Apps Use The S Pen?

This is a good question, actually. In preparing for this article, I downloaded the S Pen SDK (Software Development Kit) from Samsung and looked through some of the included code samples.

Somewhat to my surprise, the code for using the S Pen was readable and easy to understand. In fact, most of the code can be abstracted away so that developers can add the relevant code to their input handling while leaving most of the rest of the code unchanged.

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Sure, this is easier said than done, especially when you’re dealing with an app that has been updated time and again for bug fixes. Still, it left me surprised that we don’t see more apps in the Play Store with S Pen-specific features, especially considering the popularity of the Samsung Galaxy Note line of devices.

The most likely answer is that the S Pen already “just works” in every app, so unless it can add features that would otherwise be impossible, developers are likely to let TouchWiz make sure the S Pen works for them.

TL;DR

An electromagnetic field is generated from a circuit behind the screen. The S Pen picks this up and uses it to power itself and figure out its position relative to the screen. It sends this, along with information from the S Pen button and the nib at the end, back to the Note.

Videos

Does It Matter?

So, assuming you didn’t already know, you now know how the S Pen works. It’s cool, but is there any practical use to this knowledge? Why yes, as a matter of fact: you can now use a heavy duty screen protector or case, if you wish, without worrying about it affecting S Pen sensitivity.

Is there anything else you’d like to see us break down? Would you like to see more detail? Less detail? Let us know in the comments below.

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