Tag Archives: ad7843

A Basic Touch-screen driver for STM32

Today I completed the basic touch screen driver. The task included Learning the "Theory of Operation" of 4 wire resistive touch screens. Learning the about the working of AD7843 touch screen controller IC. Learning about the SPI peripheral of STM32 Writing basic SPI drivers (to init, read and write to SPI1) Writing basic drivers to command and read AD7843 touch screen controller. Filtering the touchscreen data using Median Filter to remove noise. Learning about the three point touch screen calibration method. Writing a routine to convert touch screen co-ordinate (ranges from 0-4095 in X and Y direction) to LCD co-ordinates. Finally ploting a cross-hair at the touched point. The final result is shown below. Then I moved on to implement a GUI 3D Button. After that I went to try a “Free Hand Drawing” application. And what I made is shown in the video below.