mbed port of FFT routines from STM32 DSP library and Ivan Mellen's implementation. Tested on LPC2368 mbed but should work on 1768 too (original code was written for Cortex-M3)
main.cpp
- Committer:
- igorsk
- Date:
- 2009-12-13
- Revision:
- 0:90ade34a3b71
File content as of revision 0:90ade34a3b71:
#include "mbed.h" #include <limits.h> DigitalOut myled(LED1); LocalFileSystem local("local"); // code from FFTCM3.s by Ivan Mellen // http://www.luminarymicro.com/component/option,com_joomlaboard/Itemid,92/func,view/id,1636/catid,6/ extern "C" void fftR4(short *y, short *x, int N); extern "C" void ifftR4(short *y, short *x, int N); // code from STM32 DSP Library /* 64 points*/ extern "C" void cr4_fft_64_stm32(void *pssOUT, void *pssIN, uint16_t Nbin); /* 256 points */ extern "C" void cr4_fft_256_stm32(void *pssOUT, void *pssIN, uint16_t Nbin); /* 1024 points */ extern "C" void cr4_fft_1024_stm32(void *pssOUT, void *pssIN, uint16_t Nbin); void test_stm32() { #define N 64 /*Number of points*/ uint32_t x[N], y[N]; /* input and output arrays */ int16_t real[N], imag[N]; /* real and imaginary arrays */ memset(real, 0, sizeof(real)); memset(imag, 0, sizeof(imag)); real[1]=SHRT_MAX; /* Fill the input array */ for (int i=0; i<N; i++) { x[i] = (((uint16_t)(real[i])) | ((uint32_t)(imag[i]<<16))); } cr4_fft_64_stm32(y, x, N); /*computes the FFT of the x[N] samples*/ FILE* log = fopen("/local/stm32.txt","w"); for (int i=0; i<N; i++) { fprintf(log, "%d: %d, %d -> %d, %d\n", i, real[i], imag[i], int16_t(y[i] & 0xFFFF), int16_t(y[i] >> 16)); } fclose(log); } void test_mellen() { short x[512]; // input data 16 bit, 4 byte aligned x0r,x0i,x1r,x1i,.... short y[512]; // output data 16 bit,4 byte aligned y0r,y0i,y1r,y1i,.... short z[512]; // same format... for (int i=0;i<512;i++) x[i]=0; for (int i=0;i<512;i=i+8) { x[i+0]=16384; x[i+2]=16384; x[i+4]=-16384; x[i+6]=-16384;} // x = [ 16384,16384,-16384,-16384,16384,...] 1/4 Fsampling //call functions fftR4(y, x, 256); // y is in frequency domain y[128]= printf("fftR4 ok\n"); ifftR4(z, y, 256); // z should be x/N + noise introduced by 16 bit truncating printf("ifftR4 ok\n"); FILE* log = fopen("/local/mellen.txt","w"); for (int i=0; i<256; i++) { fprintf(log, "%d: %d -> %d -> %d\n", i, x[i], y[i], z[i]); } fclose(log); } int main() { printf("Testing Mellen\n"); test_mellen(); printf("Testing STM32\n"); test_stm32(); printf("Done\n"); }