[问答]

FFT功率谱问题

1547 FFT

问答对人有帮助，内容完整，我也想知道答案 0 您好，抱歉我的英语不好。我可以在FFTBuffic中获得FFT频谱，但是不能得到FrimeSuffRealEdCurx（）的功率谱。我的代码有什么问题，或者程序参数错误吗？我使用DSPIC33 FJ64 GP802。有人请告诉我。以上来自于百度翻译以下为原文 Hi, sorry for my bad English. I can get FFT spectrum in fftbuffer, but can not get power spectrum generated by the function SquareMagnitudeCplx(). Is there something wrong with my code, or program parameter wrong? i use dsPIC33FJ64GP802. Someone please tell me. #include #include #include #include #include #define LOG2N 7 #define FFT_SIZE 128 //=2^7 #define NUM_TAPS 138 unsigned int Index; unsigned int flag; fractional SigIn[FFT_SIZE]; fractional FilterOut[FFT_SIZE]; fractcomplex fftBuffer[ FFT_SIZE ] __attribute__ ((space(ymemory), aligned (FFT_SIZE * 2 * 2))); // Place fftBuffer in Y-memory aligned to the size the array in bytes fractional window[FFT_SIZE]; // Hamming window fractional powerspec[FFT_SIZE]; // Power Spectrum fractcomplex twiddleFactors[ FFT_SIZE/2 ]__attribute__((space(xmemory))); fractional _YBSS(128) delay[FFT_SIZE]; const fractional lpfCoeffs[NUM_TAPS] __attribute__ ((space(auto_psv), aligned (FFT_SIZE * 2 * 2))) ={ 1424,-2012,-1898,131,4372,8848,10772,8848,4372,131,-1898,-2012,1424 }; //filter coefficient FIRStruct LPF; //LPF fc1=1000 fc2=2000 void initADC(void) { AD1PCFGL = 0x03C0; //AN0-3 analog AD1CON1bits.SSRC = 2; //Internal counter ends sampling and starts conversion (auto-convert) AD1CON1bits.AD12B = 1; //12-bit, 1-channel ADC operation AD1CON1bits.ADON = 1; //ADC module is operating AD1CON1bits.ASAM = 1; AD1CON2 = 0x00; //ADCON2 no scan AD1CON3bits.SAMC = 0; //Autosample time AD1CON3 = 0b0000000000001001; // Tad={Tcy(ADCS+1)}/2>334ns, Then ADCS>18.7, Tad=10Tcy AD1PCFGL=0xFFFF; //AD1PCFGH=0xFFFF; AD1CSSL = 0b0000000000000000; AD1PCFGLbits.PCFG1 = 0; //port pin in analogmode, port read input disabled, ADC samples pin voltage IFS0bits.AD1IF = 0; // Clear the A/D interrupt flag bit IEC0bits.AD1IE = 0; // Do Not Enable A/D interrupt } //return ADC result 32uS@Tcy=36.85MHz unsigned int readADC() { AD1CHS0 = 0x0001; //input channel in this AN1 is input AD1CON1bits.SAMP = 1; // ADC Sample Enable bit while(!AD1CON1bits.DONE); //wait until done ADC AD1CON1bits.DONE=0; //status = 0 return ADC1BUF0; //result } // Timer subroutine void __attribute__((interrupt, auto_psv)) _T3Interrupt(void) { IFS0bits.T3IF = 0; while(!IFS0bits.AD1IF); SigIn[Index++] = readADC(); //FIR (FFT_SIZE, &FilterOut[Index++], &SigIn[Index++], &HPF); if(Index == FFT_SIZE) { T3CONbits.TON = 0; flag = 1; } IFS0bits.AD1IF = 0; IFS0bits.T3IF = 0; } int main(void) { int i, j, k; /// Initialize Clock OSCCON = 0x00300; // PRIPLL?? CLKDIV = 0x0100; // prescaler set1:2 PLLFBD = 0x0026; // 40times?8MHz÷2×40÷2 = 80MHz RCONbits.SWDTEN = 0; //watchdog timer off initADC(); OpenTimer3(T3_ON & T3_GATE_OFF & T3_PS_1_1 &T3_SOURCE_INT, 1600-1); ConfigIntTimer3(T3_INT_PRIOR_5 & T3_INT_ON); /// T3setting:T3= 10kHz = 16000kHz / 1600 flag = 0; Index = 0; TwidFactorInit(LOG2N, twiddleFactors, 0); HammingInit (FFT_SIZE, window); FIRStructInit( &LPF, NUM_TAPS, (fractional )lpfCoeffs, PSVPAG, delay ); FIRDelayInit (&LPF); DISICNT = 0x0000; //enable interruput while(1) { //while(!flag); flag = 0; fftBuffer[0].real = 0; fftBuffer[1].real = 0; for(j = 0; j < FFT_SIZE; j++) FIR (1, &FilterOut[j], &SigIn[j], &LPF); VectorWindow(FFT_SIZE, FilterOut, FilterOut, window); for(i = 2; i < FFT_SIZE; i++) { fftBuffer.real = FilterOut; fftBuffer.imag = 0; } FFTComplexIP(LOG2N, fftBuffer, twiddleFactors, COEFFS_IN_DATA); BitReverseComplex(LOG2N, fftBuffer ); SquareMagnitudeCplx( FFT_SIZE , fftBuffer, powerspec); 0
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