Design And Realization Of Electronic Whiteboard Based On Infrared Ray

Electronic whiteboard develops with multimedia technology, computer technology and display technology at the end of the 20th century,it is a multimedia tool which can be used in teaching, conferences, presentations, training and so on. It makes traditional teaching and demonstration teaching method combined. We can impart information to others more directly, more simply and more vividly through it. Whiteboard has been becoming a teaching tool liked by teachers and classmates in foreign countries.Now, positioning technology used in electronic whiteboard mainly include resistance membrane technology, electromagnetic induction technology, infrared technology, ultrasonic technology and CCD technology, according to different technologies can be divided into different types of whiteboard. With the users'require the performance of whiteboard becomes higher and higher, many manufacturers begin to use a variety of technology integration positioning mode, such as positioning method with infrared and ultrasonic, positioning method with infrared and Mike.Currently, analog-to-digital conversion technology is used in infrared electronic whiteboard. It improves the positioning accuracy to some extent. Through using modulated infrared drivers to enhance the anti-jamming capability; Infrared electronic whiteboard uses matrix-model to improve positioning accuracy and scanning speed; Increase gesture recognition. Infrared electronic whiteboard can identify one and more touches. With the improvement of the technology, infrared electronic whiteboard has an increasing application, including education system, financial transaction system, public information and inquiry services, entertainment and so on.Electronic whiteboard based on infrared ray achieves real-time positioning through infrared scanning, so current, voltage, static electricity and noise can't affect the system. At the same time, Infrared whiteboard has many other advantages, such as: can use finger and teacher's pointer to write and touch without special pen; not afraid to scratch, even if there is any scratch, it does not affect the operation; long life; fast response; strong anti-interference ability. But the positioning accuracy of infrared electronic whiteboard is not high, so this thesis gives a new structure and positioning algorithm of infrared electronic whiteboard.Because infrared electronic whiteboard has a low positioning accuracy, so this thesis studied the theory and positioning of infrared electronic whiteboard, and put forward a system structure and positioning algorithm. It completes the overall design of hardware circuits and system software design, and realizes the function of touch location, enhance the positioning accuracy.The main work and contents are summed up as follows.Chapter one introduces the background of infrared electronic whiteboard and research at home and abroad, also introduces infrared whiteboard system composition and characteristics, and put forward the contents of this thesis.Chapter two introduces some positioning methods about infrared electronic whiteboard, and puts forward my own positioning algorithm in accordance with these positioning methods.Chapter three introduces the hardware circuits of infrared electronic whiteboard. Hardware circuits including control circuits, infrared driver circuit and infrared signal processing circuit and the serial communication circuit design.Chapter four introduces the program of infrared electronic whiteboard. The program mainly contain AGC table generation, reference table generation, detect program of touch, interrupt program, A/D sampling procedures and serial the design of communication program.Chapter five introduces problems encountered at the process of debugging. Chapter six, it is a summary of the full text, and points out the future work and direction.The main contribution of this paper is listed as follow:(1) Putting forward my own positioning algorithm by summing the positioning methods of infrared electronic whiteboard. (2) Have completed the design and realization of the hardware circuit of infrared electronic whiteboard system, and realized the complex logic control and the positioning algorithm.(3) Have completed AGC which control the range of infrared signal.(4) Have realized the overall scanning and key scanning in the infrared electronic whiteboard, which greatly enhance the scanning speed of infrared electronic whiteboard.(5) Have completed the generation of AGC table and reference table.(6) Product PCB circuit board many times, debugging the entire system and testing the system.The innovations of this paper are as follows:(1) Putting forward a new positioning method, it reduces requirements of the performance of infrared transmitters, at the same time, it has a simple algorithm, easily realized and high positioning accuracy compare with other positioning method.(2) Giving a key scan method. This method can greatly improve the scanning speed of infrared system especially in large-size infrared whiteboard, and reduce the differences in response speed between different sizes.(3) Putting forward a concept of auto-refresh in AGC table and reference table. It reduces the impact on system performance because of infrared tube aging and surrounding environment changes.