/*FFT128C.C - REAL-VALUED FFT WITH 128 POINTS. CALLS FFT_RL.ASM      */
#include "math.h"                           /*standard library func  */
#include "aiccomc.c"                        /*AIC comm routines      */
#define N 128                               /*size of FFT            */
#define M 7                                 /*number of stages       */
volatile int index = 0;                     /*input_output index     */
float *IO_buffer, *data, *temp;             /*--> array buffers      */
int AICSEC[4] = {0x162C,0x1,0x3872,0x67};   /*AIC config data        */
extern void fft_rl(int, int, float *);      /*fft function protype   */

void c_int05()                              /*interrupt handler func */
{
 PBASE[0x48] = ((int)(IO_buffer[index])) << 2;          /*output data*/
 IO_buffer[index] = (float)(PBASE[0x4C] << 16 >> 18);   /*input data */
 if (++index >= N) index = 0;            /*increment index, reset = N*/
}

main()
{
 int loop;                               /* declare variable         */
 float real, img;                        /* declare variables        */
 AICSET_I();                             /*config AIC for interrupt  */
 IO_buffer = (float *) calloc(N, sizeof(float)); /*input_out buffer  */
 data = (float *) calloc(N, sizeof(float)); /* fft data buffer       */
 while (1)                               /* create endless loop      */
 {
  fft_rl(N, M, (float *)data);           /*call FFT function         */
  data[0] = sqrt(data[0]*data[0])/N;     /*magnitude of X(0)         */
  for (loop = 1; loop < N/2; loop++)     /*calculate X(1)..X(N/2-1)  */
  {                                    
   real = data[loop];                    /*real part                 */
   img = data[N-loop];                   /*imaginary part            */
   data[loop] = sqrt(real*real+img*img)/N;  /*find magnitude         */
  }
  data[N/2] = sqrt(data[N/2]*data[N/2])/N;  /*magnitude of X(N/2)    */
  for (loop = N/2+1; loop < N; loop++)   /*X(N/2+1).. X(N-1)         */
   data[loop] = data[N-loop];            /*use symetry               */ 
  while (index);                         /*wait till IO_buffer empty */
  temp = data;                           /*temp => data buffer       */
  data = IO_buffer;                      /*IO_buffer-->data buffer   */
  IO_buffer = temp;                      /*data buffer->new IO_buffer*/
  IO_buffer[0] = -2048;                  /*sync pulse,negative spike */
 }
}