CODEWITHSUNDEEP
iphoneiosipadtouch
Hlung
Hlung

Reputation: 14308

In what time interval do these devices use to sample each touch coordinate?

I'm wondering what is the latency (or sensitivity) of iOS devices such as iPad or iPhone. In other words, in what time interval do these devices use to sample each touch coordinate. I came across this video and just got curious. http://www.youtube.com/watch?feature=player_embedded&v=vOvQCPLkPt4#

Upvotes: 1

Views: 135

Answers (1)

Rok Jarc
Rok Jarc

Reputation: 18875

This is actually more of a hardware-related question.

There are two ways to implement a touch screen in a device such as iPhone:

  • interrupt
  • continious loop

Actually (for efficiency sake) usually a combination is used: interrupt let's the OS (actually the processor on which OS is running) know that it should pay more attention to touchscreen when something is going on up there.

And to answer your question: when something is going on on the touchscreen it's all up to the processor and it's speed (clock) and the percent of CPU time that it can devote to tracking the ongoing touches. So this is device-dependant.

If you want to get a quick feeling on the speed of scanning you can subclass some view and put a NSLog statement inside touchesMoved event printing out the timestamps of the events fired.

EDIT: most commonly mentioned scanning update for iOS devices is 60Hz (update each 16.7ms) but you shouldn't take it for granted.

Upvotes: 1

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