interfacing touch panel with arm7 friendly

Posted on Feb 4, 2014

A touch screen is an electronic visual display that can detect the presence and location of a touch within the display area. The term generally refers to touching the display of the device with a finger or hand. Touch screens can also sense other passive objects, such as a stylus. Fig. 1 shows how to interface the touch panel into microcontroller.

interfacing touch panel with arm7 friendly
Click here to download the full size of the above Circuit.

To read the position of the touch, we have to first read touch position sequentially i. e. first read X position and then read the Y position. To do this, connect X1 and Y2 pins of touch screen to ADC multiplexed GPIO pins of the controller. And connect X2 and Y1 pins of touch screen to simple GPIO pins of the microcontroller. To Interface touch screen with a microcontroller, we will need a two or more channels of Analog-to-Digital converter. This is needed because, the touch screen will provide data in terms of an analog voltage on two different pins, using which, we have to determine position of the touch. Also, ADC input pins of the microcontroller should be configurable as General Purpose I/O (GPIO). The ARM7 LPC2148 Evaluation board has four numbers of Touch panel connections, connected with I/O Port lines (P1. 20 P1. 21 && P0. 29 P0. 30) to make touch panel output. The Interfacing touch panel with LPC2148 program is very simple and straight forward, that display a text in 128 X 64 GLCD module when touch the touch panel. Some delay is occurring when a single command / data is executed. To compile the above C code you need the KEIL software. They must be properly set up and a project with correct settings must be created in order to compile the code. To compile the above code, the C file must be added to the project. In Keil, you want to develop or debug the project without any hardware setup. You must compile the code...

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