How The Touch Screen Works.

Discussion in 'iPod touch' started by Ejizzle4550, Jul 26, 2008.

  1. Ejizzle4550

    Ejizzle4550 New Member

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    How the touch screen works. New Information Added!!

    This is for every person who ever wondered how in the world the iPhones touch screen works!! Ill add more to how the GUI works and about the iPhone for all the noobs like me who had no idea how it works. until now...

    The basic idea is pretty simple -- when you place your finger or a stylus on the screen, it changes the state that the device is monitoring. In screens that rely on sound or light waves, your finger physically blocks or reflects some of the waves. Capacitive touch-screens use a layer of capacitive material to hold an electrical charge; touching the screen changes the amount of charge at a specific point of contact. In resistive screens, the pressure from your finger causes conductive and resistive layers of circuitry to touch each other, changing the circuits' resistance.


    Most of the time, these systems are good at detecting the location of exactly one touch. If you try to touch the screen in several places at once, the results can be erratic. Some screens simply disregard all touches after the first one. Others can detect simultaneous touches, but their software can't calculate the location of each one accurately. There are several reasons for this, including:

    Many systems detect changes along an axis or in a specific direction instead of at each point on the screen.
    Some screens rely on system-wide averages to determine touch locations.
    Some systems take measurements by first establishing a baseline. When you touch the screen, you create a new baseline. Adding another touch causes the system to take a measurement using the wrong baseline as a starting point.
    [​IMG]

    Multi-touch Systems
    To allow people to use touch commands that require multiple fingers, the iPhone uses a new arrangement of existing technology. Its touch-sensitive screen includes a layer of capacitive material, just like many other touch-screens. However, the iPhone's capacitors are arranged according to a coordinate system. Its circuitry can sense changes at each point along the grid. In other words, every point on the grid generates its own signal when touched and relays that signal to the iPhone's processor. This allows the phone to determine the location and movement of simultaneous touches in multiple locations. Because of its reliance on this capacitive material, the iPhone works only if you touch it with your fingertip -- it won't work if you use a stylus or wear non-conductive gloves.

    [​IMG]

    Interpreting Touch-location Data

    The iPhone's processor and software are central to correctly interpreting input from the touch-screen. The capacitive material sends raw touch-location data to the iPhone's processor. The processor uses software located in the iPhone's memory to interpret the raw data as commands and gestures. Here's what happens:

    Signals travel from the touch screen to the processor as electrical impulses.
    The processor uses software to analyze the data and determine the features of each touch. This includes size, shape and location of the affected area on the screen. If necessary, the processor arranges touches with similar features into groups. If you move your finger, the processor calculates the difference between the starting point and ending point of your touch.
    [​IMG]
    The processor uses its gesture-interpretation software to determine which gesture you made. It combines your physical movement with information about which application you were using and what the application was doing when you touched the screen.
    The processor relays your instructions to the program in use. If necessary, it also sends commands to the iPhone's screen and other hardware. If the raw data doesn't match any applicable gestures or commands, the iPhone disregards it as an extraneous touch.
    [​IMG]
    All these steps happen in an instant -- you see changes in the screen based on your input almost instantly. This process allows you to access and use all of the iPhone's applications with your fingers. We'll look at these programs and the iPhone's other features in more detail in the next section, as well as how the iPhone's cost measures up to its abilities.


    To all who read, well, you can thank www.howstuffworks.com for all of the above information. didnt know the rules about off-site links so i just copied and pasted.
    Want to know more? go to www.howstuffworks.com and search iPhone :)
    MODS, if i can't post those two above links let me know and i will remove them. Thank you.

    i just got bored and wondered how in the world the touchscreen works.

    EDIT: here is a link to my homemade stylus that is easy to make and works like a charm!
    http://www.ifans.com/forums/showthread.php?t=39647&highlight=ejizzle4550

    One more edit: To keep this as legal as i can for all who are to lazy to read links, here is a link to the sources page.
    http://electronics.howstuffworks.com/iphone6.htm
  2. RenegadeKrogan

    RenegadeKrogan Banned

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    Thanks! This was really informative and makes a lot of sense to hy you cannot use a stylus with the touch.
  3. Ejizzle4550

    Ejizzle4550 New Member

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    thank you, lol..
    this is what happens when people get bored and look for stuff.
    and if you search for my post about working styluses that I've made you can make them yourself :)
  4. RenegadeKrogan

    RenegadeKrogan Banned

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    Yeah. I will look it up.
  5. Ejizzle4550

    Ejizzle4550 New Member

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    let me know if you find it.
  6. thechungster

    thechungster Super Moderator Emeritus

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    wow thats cool on how it works.
  7. Ejizzle4550

    Ejizzle4550 New Member

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    ya, i was loooking for it everywhere and my friends like, i bet you 50 bucks that howstuffworks will have it on there...and i was like no waayyy lol
    but sure enough it was there..i was surprised.
  8. royalblue

    royalblue Banned

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    it's cool how you can actually see the little grid on the screen if it's very clean and you look very closely
  9. Halacio

    Halacio New Member

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    looks stupid when you can see it i only did once in bright bright sunlight.
  10. plokiju

    plokiju New Member

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    I actually wrote an essay about this in Science in October.

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