Design And Realization Of Digital Wireless Location Electronic Whiteboard

With the development of information teaching technology, education models have had a rapid change. As electronic interactive whiteboard has the real-time operation and vivid display features, It will play a great role in the information teaching. Laboratory had developed the first generation of electronic whiteboard based on the theory of wireless location in 2003, which filled the gap in the country. In order to improve the performance of the system, the laboratory started to develop the digital wireless location electronic whiteboard.In this thesis, the Digital Wireless Location Electronic Whiteboard is consisted of the low-noise receiving analog circuits, signal processing module which includes DSP-CPLD core. It is portable, easy to upgrade, environmental adaptability.The thesis expounds the evolution and background of the whiteboard. It describes the development and classification of interactive whiteboard in details It also analyses several mainstream two-dimensional location technology. The paper analyses the principle of ultrasonic technology and digital wireless location electronic whiteboard in ditails.Analysing interference in the infrared and ultrasonic signal receiver, the thesis tests the characteristics of the infrared signal and ultrasonic signal. Then it designs adaptive anti-interference circuit of low-noise infrared receiver circuit. AGC circuit of ultrasounic receiver circuit is designed and implemented. In the signal processing circuit, It uses TI's TMS320VC5416 as the core of processor and development a logic circuit procedures under Maxplus environment. The thesis completes the design and realization of the signal processing, including A/D acquisition, digital signal processing module, a large-scale logic circuit module, power supply and storage design, USB communication circuit design.In order to improve the location accuracy, the thesis analyzes several ultrasonic localization algorithms. Based on in-depth studing of ultrasound transmission characteristics in different locations, plate and environment, it synthesizes the zero-crossing comparison detection algorithm, the dynamic dual-threshold detection algorithm and correlation detection algorithm integrated. The paper used the algorithm in several different location situation based on the characteristics of the ultrasound, and programming on the hardware. Many subprogrammes are introduced, such as software filtering, anti-infrared procedures and bootloader.The paper tests a comprehensive performance for the Digital Wireless Location Electronic Whiteboard, including the wave testing, written testing, performance testing, interactive mode of the test, reliability testing and aging testing. The results show that the system work stable and reliable in a complex environment.Main content of this thesisChapter 1 summarizes the background, evolution process and the present situation of whitebroad. It analyses the advantages and disadvantages of interactive whiteboard. The chapter also analyses the foundation of the research and the characteristics of the digital whiteboard. It describes the composition, performance indicators and the function of Digital Wireless Location Electronic Whiteboard. Finally, it introduces the content and the researching purport of this thesis.Chapter 2 analysises the characteristics of several mainstream two-dimensional location technology. Based on that, the thesis elaborates location principle of the ultrasonic and the system. The coordinate transformation simplifies the calculating of the system.Chapter 3 introduces the principles and the design of infrared, ultrasonic signal transmission and reception of the Digital Wireless Location Electronic Whiteboard. This chapter tests characteristics of the infrared signal, and designs adaptive anti-interference circuit, low-noise circuit and anti-jamming circuit. These circuits solve the spines in near distance and too small signal in long-distance, the static noise and signal interference on the system. The thesis designs ultrasonic recerver circuit with AGC circuit and DC bias. The circuit improves the quality of the waveform, provids a good receiver for the signal processing .Chapter 4 completes the design and implementation of the digital part. It uses TI's TMS320VC5416 as the core of processor and developments a logic circuit procedures under MaxplusⅡenvironment. The chapter completes the design and realization of the signal processing, which including A/D acquisition, digital signal processing module, a large-scale logic circuit module, power supply and storage design, USB communication circuit.Chapter 5 introduces several ultrasound localization algorithms at first. It synthesizes the zero-crossing comparison detection algorithm, the dynamic dual-threshold detection algorithm and correlation detection algorithm to complete the location Based on in-depth studing of ultrasound transmission characteristics in different locations, plate and environment.This chapter uses these algorithms in several different location based on the characteristics of the variable ultrasound, and programming on the hardware. Many subprogrammes are introduced in the chapter, such as software filtering, anti-infrared procedures and bootloader.Chapter 6 analysises the modify and debug problems and the process of the solutions in the realization of the Digital Wireless Location Electronic Whiteboard base on the Signal Integrity and and Electromagnetic Compatibility. For four times of PCB and debugging, the chapter realizes the stable and reliable system.After completion of the production of a prototype, in order to verify system stability, a small trial production of prototype and debug are done as an example, the charpter does an in-depth analysis on problems found in the experiment. Chapter 7 tests a comprehensive performance for the Digital Wireless Location Electronic Whiteboard.The test includes wave testing, written testing, performance testing, interactive mode testing, reliability testing and aging testing. Test results show that the system can have a well full-screen writing on a variety of plate surface, which achieves the portability ability. The location accuracy of the system is 0.5mm. Its writing is good symmetry. Rapid writing speed can achieve 6m/s, and slow writing is non-overlapping. System works well in the interactive mode. It also performs well in light, temperature, night and artificial interference. System can continuous work more than 51 hours in the test.Chapter 8 summarizes the conclusion of the thesis.The innovative work of this thesis1. The thesis synthesizes the zero-crossing detection comparison algorithm, the dynamic dual-threshold detection algorithm and correlation detection algorithm to complete the location based on in-depth studing of ultrasound transmission characteristics in different locations, plate and environment. The thesis uses these algorithms in several different locations based on the characteristics of the variable ultrasound, and programmes on the hardware based on DSP–CPLD core. It solves the adaptability of system in different plate surfaces and environment.2. The thesis designs adaptive anti-interference circuit for infrared receiver which improves the reception quality of the infrared, reduces the interference of the spines in 30cm. The circuit makes the Infrared signal receiving distance increase from 2.5m to 3.5m.3. The design of AGC for ultrasonic circuit combined with distance and magnitude of software-controlled gain adjustment solves the problem of saturation phenomenon of ultrasound signal caused by the board expansion when the magnification is fixed. It also improves the ultrasound signal upward trend and achieves good amplification on 1.8m×2.4m writing plate surface.With the problems summarized In the tests, in order to enhance the localization of the digital wireless whiteboard, we need to improve the omni-directional reception of ultrasound and development the temperature control module.