2 u014607705 u014607705 于 2014.04.08 17:20 提问

救助 急急急。DSP C5515 怎么调用dsplib 里 rifft()和cbrev()转回时域。

代码里已经给出来 fft后,在c5515的显示屏上出现了bargraph的图案,转到了频域。如何再调用dsplib里的rifft()和cbrev()转回时域,并且在显示屏上出来正弦波?``代码如下,如果我再写一个ifft的子函数,我是不是要新定义一个buffer 然后input是calculate_power 的buffer?

#include "stdio.h"
#include "usbstk5515.h"
#include "usbstk5515_led.h"
#include "aic3204.h"
#include "PLL.h"
#include "bargraph.h"
#include "oled.h"
#include "pushbuttons.h"
#include "stereo.h"
#include "dsplib.h"

Int16 left_input;
Int16 right_input;
Int16 left_output;
Int16 right_output;
Int16 mono_input;

#define SAMPLES_PER_SECOND 8000

/* Use 20 for guitar */
#define GAIN_IN_dB 0

unsigned long int i = 0;

unsigned int Step = 0;
unsigned int LastStep = 99;

int j = 0;
int k = 0;
int m = 0;
int display_counter = 0;
int waveform_counter;
long delay;

DATA input_buffer[1024]; /* Must be declared as DATA for dsplib compatibility */

DATA buffer2[1024];
int display_buffer[96];
int buffer1[96];

/*****************************************************************************/
/* calculate_power() /
/
---------------------------------------------------------------------------*/
/* /
/
Parameter 1: Real term a. /
/
Parameter 2: Immaginary term jb. /
/
/
/
RETURNS: a*a + b*b. Result will always be positive. /
/
/
/
****************************************************************************/

int calculate_power (int a, int b)
{

return ( (int) ( ( (long)a * a + (long) b * b) >> 14) );
}

/*****************************************************************************/
/* calculate_FFT() /
/
---------------------------------------------------------------------------*/
/* /
/
Parameter 1: Latest audio input (real value). /
/
Parameter 2: size of FFT e.g. 128, 512 and 1024 elements. /
/
/
/
RETURNS: None. /
/
/
/
****************************************************************************/

void calculate_FFT(int input, int size)
{
static int i = 0;
static int counter = 0;

buffer2[i] = input; /* Store as a real value /
i++;
buffer2[i] = 0; /
Store with an imaginary value of 0 */
i++;

if ( i >= size-1)
{
i = 0;

/* Perform complex FFT using N real and N imaginary values */

cfft (&buffer2[0], size/2, SCALE);

cbrev(&buffer2[0], &buffer2[0], size/2);

for ( j = 0 ; j < 96 ; j ++)
 {
  display_buffer[j] = calculate_power((int) buffer2[2*j], (int)buffer2[2*j+1]); 
 }

counter++;
if ( counter >= 1)
{
  /* Slow down the number of updates to make display easier to see */   
  counter = 0;  
  oled_display_bargraph( &display_buffer[0]);
}     

}
}

/* ------------------------------------------------------------------------ *

  • *
  • main( ) *
  • *
  • ------------------------------------------------------------------------ /
    void main( void )
    {
    /
    Initialize BSL */
    USBSTK5515_init( );

    /* Initialize PLL */
    pll_frequency_setup(120);

    /* Initialise hardware interface and I2C for code */
    aic3204_hardware_init();

    /* Initialise the AIC3204 codec */
    aic3204_init();

    /* Turn off the 4 coloured LEDs */
    USBSTK5515_ULED_init();

    /* Initialise the OLED LCD display /
    oled_init();
    SAR_init();
    /
    Flush display buffer */
    oled_display_message(" ", " ");

    printf("\n\nRunning Project Spectrum Analyser\n");
    printf( "<-> Audio Loopback from Microphone In --> to Headphones/Lineout\n\n" );

    /* Setup sampling frequency and 30dB gain for microphone */
    set_sampling_frequency_and_gain(SAMPLES_PER_SECOND, GAIN_IN_dB);

    oled_display_message("Application 20 ", "Spectrum Analyser ");

    /* New. Add descriptive text */
    puts("\n Bargraph at 6dB intervals");
    puts("\n Press SW1 for DOWN, SW2 for UP, SW1 + SW2 for reset\n");
    puts(" Step 1 = Straight through, no signal processing. Set levels");
    puts(" Step 2 = Waveform view");
    puts(" Step 3 = FFT 1024 Display. Calculate power and display as bargraph");
    puts(" Step 4 = FFT 512 Display. Calculate power and display as bargraph");

    /* Default to XF LED off */
    asm(" bclr XF");

    for ( i = 0 ; i < SAMPLES_PER_SECOND * 600L ;i++ )
    {

    aic3204_codec_read(&left_input, &right_input); // Configured for one interrupt per two channels.

    mono_input = stereo_to_mono(left_input, right_input);

    Step = pushbuttons_read(4);

    if ( Step == 1 )
    {
    if ( Step != LastStep )
    {
    oled_display_message("STEP1 No Processing", "Set Levels ");
    LastStep = Step;

      } 
     left_output = left_input;      // Straight trough. No processing.
     right_output = right_input;
    
    } 
    

    else if ( Step == 2)
    {
    if ( Step != LastStep)
    {
    oled_display_message("STEP2 ", " Waveform View");
    LastStep = Step;
    display_counter = 0;
    waveform_counter = 0;
    }

     if ( display_counter < 8000)
       {
        display_counter++;
       } 
    
     if (display_counter >= 8000)
       {
        buffer1[k] = mono_input;
        k++;
    
        if ( k >= 96)
         {
           k = 0;   
           waveform_counter++;
           if ( waveform_counter >= 6)
             {
               waveform_counter = 0;    
               oled_display_waveform(&buffer1[0]);
               delay = 0xFFFFFF;
               while ( delay--)
                {
                 /* Wait */ 
                }   
             }  
         }
    
       }
    
    } 
    

    else if ( Step == 3)
    {
    if ( Step != LastStep)
    {
    oled_display_message("STEP3 ", " FFT 1024 Display");
    LastStep = Step;
    display_counter = 0;
    }

     if ( display_counter < 8000)
       {
        display_counter++;
       } 
    
     if (display_counter >= 8000)
       {  
        calculate_FFT(mono_input, 1024);
       }
    }  
    

    else if ( Step == 4)
    {
    if ( Step != LastStep)
    {
    oled_display_message("STEP4 ", " FFT 512 Display");
    LastStep = Step;
    display_counter = 0;
    }

     if ( display_counter < 8000)
       {
        display_counter++;
       } 
    
     if (display_counter >= 8000)
       {  
        calculate_FFT(mono_input, 512);
       }                
    
    }   
    

    aic3204_codec_write(left_output, right_output);

    if ( Step == 1)
    {
    /* Only display bargraph when setting up. Distracting otherwise */

    bargraph_6dB(left_output, right_output);
    }
    }

    /* Disable I2S and put codec into reset */
    aic3204_disable();

    printf( "\n***Program has Terminated***\n" );

    oled_display_message("PROGRAM HAS ", "TERMINATED ");

    SW_BREAKPOINT;
    }

/* ------------------------------------------------------------------------ *

  • *
  • End of main.c *
  • *
  • ------------------------------------------------------------------------ */
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