在DSP中，对回波数据进行FFT处理将其变换到频域后，将其与频域系数进行点积，对点乘结果再做一次逆FFT，将频域结果转换到时域，在这一步中需要调用函数fft_flp32.asm，其功能是实现输入数据的FFT变换。-In DSP, FFT processing of echo data to be transformed into the frequency domain, the frequency-domain coefficients with the dot product, the results point to do it again by the inverse FFT, the results of frequency domain to time domain conversion, in this step need to call the function fft_flp32.asm, its function is to transform the input data of the FFT.