The Design And Implementation Of The Anti Strong Light And Multiple-spot Infrared Touching Screen Base On STM32

Single-point touch technology cannot meet the demand of our work, study andentertainment anymore, hence developing Multi-touch technology will prevail for sure.So far there’re a lot of touching screen can support Multi-touch, and are used in manydifferent fields according to their different characteristics. Infrared touching screen has ahistory of decades, for infrared touching screen has no drift, it is immune to theinterferences from the current, voltage and static electricity, and has the virtue of highlight transmission rate, hence infrared touching screen is getting more and more popular.But infrared touching screen has some deficiency that has not been solved yet, forexample, infrared touching screen has problems on resisting ambient light interference,thus it is mostly confined in the environment with low interference. This project hasdesigned and developed anti strong light multi-spot infrared touching screen based onthe STM32chip through researching the works of touching and infrared touchingscreen’s deficiencies.The hardware of this system is as follows, the main controller is STM32, throughcontrolling the logic chip to achieve matrix scanning from infrared touching screen. Thesignal collecting part is achieved by the high pass filter formed by capacitor and analogswitch. High-performance Op-amp chips and the digital potentiometer are chosen toform the AGC, thus on one hand enhances the useful life of the infrared touching screen,and on the other hand enhance the infrared touching screen’s ability to resist theenvironment light interference. This system uses USB for communication and electronicsupply, it is plug and play, XP and WIN7OS supporting, and WIN7OS can achievemulti-spot touching directly.This system adopts many different software methods to enhance the function of theinfrared touching screen. The idea of one transmitting and two receiving and movingaveraging filter are adopted to enhance its precision. A redundancy designing idea isproposed to enhance the useful life of the infrared touching screen. In the process ofachieving the real multi-spot touching by analyzing the false point problem, the methodof tile scan is used to get rid of the false point. And in the end an algorithm is proposed to get rid of the false point, and the system can achieve the real multi-spot touching.This project can achieve real two spot touching with infrared touching, it has thequality of high ability of resisting the disturbance from the light, and it can resist more50,000Lx sunlight interference and make it perfect to use in outdoor situation. With theresolution of4096*4096and the precision of less than5mm, and responding quickly,long useful time and low cost, make it has deep project significance and highcommercial value.