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CFAG320240CX-TFH-T-TS controller

manju

New member
I have purchased a touchscreen LCD(CFAG320240CX-TFH-T-TS).It seems it has a 4 wire analog o/p for the touch i/p.I want to convert the analog o/p to digital signal (H-3.3V,L-0V) for the TMS320F2812 DSP.Can anyone suggest a suitable controller for that.
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CF Support2

Administrator
(updated links)

The touch screen is an "Analog 4-wire" there is no controller on board.

The touch screen must be driven in one direction, then read in the other direction. TI makes a low-level part that has the drivers and ADC built into one part. Some micros have analog inputs that may work directly. There is a company http://www.tsharc.com/ that makes a high-level controller from a pre-programmed PIC micro.

Basically you put a gradient across one set of electrodes (both set as digital outputs, drive one high and the other low), then you look at either of the other set of electrodes (both set as inputs, at least one analog). The analog input will pick up the voltage of the gradient at the contact point. To read the other channel, you just rotate the whole process 90 degrees.

Here is a fairly in depth paper on resistive touchscreens:

http://www.monolitic.com/esp/Notas/t-screen_resistivo.pdf

Some diagrams of 4-wire:

http://www.amtouch.com.tw/basics/resistive_touch_screen_structure.htm
http://www.circuitcellar.com/library/print/0100/dahlin-114/2.htm
http://www.bergquistcompany.com/objects/Touch_PDF_Docs/4vs5wire_WHP_9.06.pdf

Understanding 4-wire analog touch screens:

http://www.howstuffworks.com/question716.htm
http://www.planetanalog.com/article/printableArticle.jhtml?articleID=199702778
http://www.touchscreens.com/intro-touchtypes-4resistive.html
http://www.hampshiretouch.com/doc/appnotes/AN103 How an Analog Resistive Touch Screen Works.pdf
http://www.touchscreens.com/intro-anatomy.html

Here is a bunch of book-marks on touchscreen controllers:

http://www.analog.com/en/prod/0,2877,AD7877,00.html
http://www.analog.com/en/prod/0,2877,AD7843,00.html
http://focus.ti.com/docs/prod/folders/print/ads7843.html
http://focus.ti.com/docs/prod/folders/print/tsc2003.html
http://focus.ti.com/docs/prod/folders/print/tsc2000.html
http://focus.ti.com/lit/ds/symlink/tsc2006.pdf
http://www.tsharc.com/
http://www.microtipsusa.com/driver_pdfs/MK715.PDF
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3402
http://www.atmel.com/dyn/resources/prod_documents/doc8091.pdf
 
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