Design And Implementation Of Capacitive Touch Key System

Capacitive Touch Keys(CTouch)has been increasingly used in advanced passenger car door control systems due to its advantages of high sensitivity,low power consumption and lack of mechanical wear.At present,the door products that use capacitive touch buttons in the market have the problems of poor environmental adaptability and poor anti-interference ability.Mainly reflected in the inability to effectively eliminate rainwater interference and electromagnetic interference,poor user experience.For capacitive touch key difference with environmental adaptability and interference suppression ability difference,this paper designed a model based on the principle of capacitance pressure capacitive touch key system,innovation of adaptive environment compensation mechanism,the Time difference algorithm(TPD,Time Per Deviation)and Peak fixed-point algorithm(FTP,Fixed Time Peak)can effectively restrain the rain interference and electromagnetic interference.The capacitive touch button system designed in this paper uses PIC16LF1559 microcontroller from Microchip Company.The design meets FAW group's JA3700-MH-3(Electromagnetic Compatibility),JA3700-MH-6(Environment and durability)and JA3700-MH-4(Electrical Performance)standards.In order to strengthen the environmental adaptability of the system,this paper proposes an adaptive environmental compensation mechanism in the detection algorithm.Four environmental detection value maintenance mechanisms,including power on maintenance,negative value maintenance,slow maintenance and overtime maintenance mechanism,are used to offset the impact brought by environmental changes.In order to improve the ability of rainwater interference and electromagnetic interference suppression,TPD algorithm and FTP algorithm are proposed.The human hand signal is recognized and the interference signal is suppressed by calculating the difference value and peak value of the signal.At the same time,in order to meet the customer's demand for online update of system software,this paper also developed the Bootloader function.The keypad system designed in this paper has passed the strict tests of the customer designated third-party testing institutions,including environmental and durability tests,electrical performance tests,electromagnetic compatibility tests and rainproof tests.The test results show that the capacitive touch keypad system designed in this paper can obtain good keypad sensing function,and has good environmental adaptability,robustness and disturbance immunity,which can meet the requirements of users.At present,the system has been applied in a high-end model,into mass production.