Mar 12 AT 11:40 AM Taylor Wimberly 31 Comments

A closer look at HTC’s touch sensors

Our recent look at the Nexus One touch screen generated a lot of questions and now we are back with some answers. The Nexus One touchscreen is not “broken” – it just suffers from a hardware limitation we were not aware of and did not perform as we expected.

For starters, let us look at the actual touch sensor used in the Nexus One. HTC selected the ClearPad 2000 capacitive touchscreen sensor. This touch sensor first debuted in 2007 and we believe HTC has used it in all their Android phones.

The ClearPad 2000 has support for “two-finger interaction and gestures” such as pinch zoom and pivot rotate, which is exactly how Google implemented it. Pinch zoom in the browser, gallery, and maps works flawlessly and we have no complaints.

The problems arise when developers try to use complex two-finger movements (like those found in games).

These multitouch issues have been well documented on the Android Developers forum and a Google employee responded with the following:

“This has nothing to do with the Android platform.  Please do not file bugs about it.  Android is just reporting what the hardware is capable of reporting.  There is no “normalization” for games or such, there is just the data the screen provides.  (Though there is some special code in the current framework for cleaning up the data from the Droid screen; arguably this should be in the driver or firmware for it, since this is really screen and hardware specific kind of stuff.  At any rate, it is not applicable to basic screen capabilities like here.)”Dianne HackbornAndroid framework engineer

The Motorola Droid features a different touch sensor (I don’t know which one. Help?) from the HTC phones and includes “some special code” which is the reason it performed better in our testing.

So what is this special code and can it be used on the Nexus One? Steve Kondik (Cyanogen) dug through the source and found the following:

Interestingly, there is a hack in the framework (which is enabled on the Droid, but not on the N1) that can be enabled by setting config_filterTouchEvents. With it disabled (the default), I get the axis-flipping problem. Enabling it fixes this, but there are still issues with the points “sticking” when they cross.CyanogenBacon lover

So as you can see, the Nexus One (and all other HTC Android phones) suffer from hardware limitations, but we could see an improvement in performance through a future software update.

Now that most of us are aware with the limitations, we know what to expect from future Android games. Developers can use two touches as long as they are careful about how they are implemented. Advanced two-finger gaming as seen on the iPhone, might never be possible because of the hardware that HTC is using.

If you want something to look forward to, check out the newer Synaptics ClearPad 3000. This touch sensor supports true multi-finger gestures and can recognize up to ten touches. Maybe HTC will pony up the cash and include it with their next superphone.

Synaptics ClearPad 3000 Series from Synaptics, Inc. on Vimeo.

Taylor is the founder of Android and Me. He resides in Dallas and carries the Samsung Galaxy S 4 and HTC One as his daily devices. Ask him a question on Twitter or Google+ and he is likely to respond. | Ethics statement

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