31階低通濾波器有限脈衝響應濾波器（Finite Impulse Response Filter，FIR Filter），此濾波器主要功能為濾除不必要的高頻訊號，其濾波器係數為固定之係數。係數在程式碼的parameter宣告中。-31-order low-pass filter finite impulse response filter (Finite Impulse Response Filter, FIR Filter), the main function of this filter is filter out unwanted high frequency signals, the filter coefficient is fixed coefficient. Factor in the code parameter declaration.