getinput.c

dsp AD公司ADSP21的代码,里面有FFT FIR IIR EQULIZER G722_21F 等可以在项目中直接应用的代码.此代码的来源是ADI公司自己出版的书籍,此书在美国购得

#include <21020.h>
#include "rtdsp.h"

/* c-code to support circular input FIFO 5-4-94 PME */
/* getinput - function to get one input sample from A/D */

    extern void int_enable(int);

extern int int_flag;

float getinput()
{
    float x;
    static int in_int_flag = 0;     /* input flag to start interupts */
    static int flag = 0;    /* 2 samples ready flag */
    static int k;
    register int j;
    int pout;

    if(flag) {
        x = (float) (k >> 16);
        flag = 0;
    }
    else {
/* if this routine has never been called then start up interupts */
        if(!in_int_flag) {
            int_enable(0);
/* record/play mode FLAG1 and FLAG3 */
            set_flag(SET_FLAG1,SET_FLAG);
            set_flag(SET_FLAG3,SET_FLAG);
            in_int_flag = 1;
        }

/* keep checking the out pointer until there are some samples in FIFO */
/* find number of samples in FIFO, take care of circular buffer problems */
        do {
          asm volatile("bit set mode1 0x18; nop; \
            r0 = i4;                  /* -out pointer */
            r0 = -r0, i2 = i3;        /* in pointer */
            m2 = r0;
            modify(i2,m2);            /* in-out */
            %0 = i2;
            bit clr mode1 0x18;  nop;" : "=d" (pout) : );
        } while(pout < 10);

/* get 2 consecutive samples from FIFO (circular buffer) */ 
        asm volatile("bit set mode1 0x18; nop;
            %0 = dm(i4,m1);
            bit clr mode1 0x18;  nop;" : "=d" (j) : );

        k = j;
        j = j << 16;    /* get sign bit */
        x = (float) (j >> 16);
        flag = 1;
    }
    return(x);
}