CFAG320240CX-TFH-T-TS controller


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.
Looking for additional LCD resources? Check out our LCD blog for the latest developments in LCD technology.

CF Support2

(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 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:

Some diagrams of 4-wire:

Understanding 4-wire analog touch screens: How an Analog Resistive Touch Screen Works.pdf

Here is a bunch of book-marks on touchscreen controllers:,2877,AD7877,00.html,2877,AD7843,00.html