| Touch screen, as the simplest and most direct way of human-computer interaction, can detect the location of the touch in the display area. Comparing with the traditional human-computer interaction device, it has touchable screen with the attribute of space saving, interface diversity, artistic design. In the existing touch technology, the infrared touching technology became the mainstream because of its simple installation, strong adaptability, massive recognized touch spots, long lifetime, etc.Traditional infrared touch technology has many defects, such as low resolution, long scan time, slow response, low accuracy of multi-touch recognition, etc. Because the response time have been raised as the key indicator for infrared touch screen, so it is very important significance to research the algorithm with high scan speed and high signal collection accuracy. Thus, this paper proposes a firmware scan algorithm to improve the infrared scan speed and the device to realize and verify it as well. The key technology and innovation are as follows:(1) The hardware design of touch screen is based on the main controller STM32, which work with Logic chips to scan touch spot matrix of the sender and receiver. The combination of STM32 and Logic chips take full advantage of strength of each other, which can speed up the scan, and lay a solid foundation to optimization of the recognition accuracy afterwards.(2) Based on the research of the full screen serial scanning in turn and full screen serial interval scanning, this paper propose and realize a new firmware scanning algorithm -tracking and forecasting scanning algorithm. This algorithm tracks the current coordinate of scanning spot to forecast the area of the next touch spot, besides, it can focus on the objective area, eliminate the unnecessary scan to speed up the scanning speed, eventually save a lot of firmware scanning time. In case of multi-touch spot, the multi-thread tracking and forecasting method, and the zigzag scanning method are deployed to remove the ghost point, speed up the response and improve the touch accuracy.(3) This paper propose a DMA firmware scanning controller based on the STM32.The DMA can control the pin of 10 interface by getting the data group successively in the DMA way to create the up and low level signal. The orderly and successive signal being created by scanning controller instead of the software instruction in the main controller, can spare time to the CPT to judge the touch spot and make scanning program and touch spot calculate program run in parallel, which improve the response time of IR touch screen in the case of no external hardware device added.Based on the upper technology and innovation, I have built an infrared touch screen system and verify it by software simulation and test on line, and finally realized the successive multi-touch spot system and achieve the objective expected. |
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