Posted on January 24, 2016 at 17:45Hi, I need do FFT on stm32f4 and therefore I
have few questions:
1. Is there any why to directly copy adc values which are uint16_t to float32_t buffer using DMA, without casting them in fork loop and using two buffers. I used this:
DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
DMA_MemoryDataSize = DMA_MemoryDataSize_Word;
but i get only zeros.
2. I tested arm_rfft_fast_f32 function from CMSIS-DSP 1.4.4 with generated 50hz sine wave at 1000Hz sample rate using 1024 samples, but i get peek value at 102, not 51 which i should get 1000/1024 ~0,97 * 51 = 50Hz:
uint16_t i;
float32_t khz10[1024];
float32_t maxvalue;
uint32_t maxindex;
//float32_t output2[1024];
arm_rfft_fast_instance_f32 S;
arm_rfft_fast_init_f32(&S, 1024);
printf(''Input=['');
for(i=0; i<1024; i++){
khz10[i] = 1.2f*arm_sin_f32(2*3.1415926f*50*i/1000)+1;
printf(''%f,'',khz10[i]);
}
printf('']\r\n'');
arm_rfft_fast_f32(&S, khz10,khz10,0);
arm_abs_f32(khz10, khz10, 1024);
arm_max_f32(khz10+1, 1023, &maxvalue, &maxindex);
printf(''Max:[%ld]:%f Output=['',maxindex,maxvalue);
for(i=0; i<1024; i++){
printf(''%f,'',khz10[i]);
}
printf('']\r\n'');
thx for help
