Design And Implement Of Capacitive Slider Sensors Base On General MCUs

Capacitive touch keys have become more widely used in the field of embedded systems because of such advantages like flexible,reliable,low consumption,no mechanical wear and so on.Domestic and foreign chip manufacturers have introduced a variety of technical solution of the capacitive touch sensor function,but its technical solution is generally in the form of “black box”,which makes the product be with limited configurability and flexibility shortage.It means to design a method to achieve the capacitive slider function by using generalpurpose microcontrollers based on capacitive sensing principle in the thesis.The realization of capacitive sensing slider system is with features of flexible configuration,reliable performance characteristics,and good universality.The researching jobs in this thesis include:(1)Describe the basic principle of capacitive sensing measurement: The realization of capacitive sensing circuit is based on the principle of capacitive voltage divider.Through a fixing process of the circuit charge and discharge operation,makes it form a positive correlation between the reference capacitor voltage and measured capacitance.It takes the voltage as the sampling objects to realize the measurement of capacitance.(2)Describe the hardware platform of capacitor slider: It takes Renasas 78K0/KC2,a general 8-bit MCU,as the controller,and in periphery using CPU I/O ports to built high-precision and high dynamic A/D conversion circuit,in order to achieve high accuracy measurement of reference capacitance voltage.(3)The design and implement of control software for capacitive slider sensor: It includes the capacitance value limiting and average filtering algorithm,the threshold setting strategy to judge the state of capacitive button,the judgement method for sliding position of the slider sensor and UART interface.With the result of the practical application and performance testing,it shows that the solution can be a good alternative to mechanical slider switch.Because capacitive slider has no mechanical wear and tear during use,it has better reliability and durability than the mechanical sliders.And it is achieved with combination of open source software in general-purpose hardware,so comparing with the existing solution,it has stronger adaptability to development environment and higher portability and debugging ability.