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Touch Screen Information


The easiest and most flexible user interface for a Liquid Crystal Display is a touch screen overlaying a Graphic LCD Module.  This allows the designer to customize their interface specifically to their application, to allow dynamic adjustments to the user interface as the product ages, and to allow for alterations required for geographically different regions.  Pacific Display Devices typically uses Analog-Resistive Touch Screens, and this approach gives use the following features:

LCD Module Touch Screens
     - Proven Resistive Technology
     - Simplicity of Interface Electronics
     - Durable Plastic Construction
     - Less Susceptible to Accidental Touch
     - Ability to use Finger or Stylus to Activate Touch Screen
     - High Linear Analog Output


Pacific Display Devices has integrated analog-resistive Touch Screen technology into our displays as an standalone feature, where the customer will integrate their own decoder, or as a fully integrated assembly, where we have integrated the full decoding electronics.  The next sections on this page will cover touch screen construction, operation, and application notes specifically set up for configurations used by Pacific Display Devices.

  LCD Touch Screen Construction and Operation
The Analog-Resistive touch screens typically used by Pacific Display Devices are constructed of two layers of electrically conductive transparent films facing one another and separated by a gasket. Each layer has a set of parallel busbars positioned along the opposite edges and orthogonal to the busbars on the other layer. Busbars consist of screen-printed conductive ink terminated at the tail. The entire switch assembly is then mounted on a rigid Glass, Acrylic of Polycarbonate backer before it is attached to the front of our LCD Modules.  Two opposing layers of Touch Screen are held apart by small separator dots until they come into contact by a light finger pressure. The voltage signal is then decoded by the controller to provide the application software with X and Y coordinates of the touch point.

  Decoder Electronics: Data Sheets and Application Notes
Decoding the analog output of the Touch Screen is relatively easy, there are many one chip solutions made by several vendors that will remove the elaborate design work.  Our primary selection for a Touch Screen controller is the ADS7843.  Here is the data sheet and application notes for this choice:

Manufactured by Burr Brown
     ADS7846 Chip Data Sheet

     ADS7846 Application notes

 


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Whatever your design needs, Pacific Display Devices has the LCD display solution


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