sendout.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 "rtdsp.h"

/* c-code to support circular output FIFO 9-4-93 PME */

    extern void int_enable(),int_disable(),flush();
    extern int play_fifo[];

/* global interrupt on flag */
    int int_flag = 0;

void sendout(float x)
{
    static int flag = 0;    /* 2 samples ready flag */
    static int k;
    register int j;
    unsigned int pin,pout;

/* round and clip to 16 bits */
    asm("r4 = fix %1;
        r2 = 32767;
        %0 = clip r4 by r2;" : "=d" (j) : "d" (x) : "r2");

/* replaces: clip output to 16 bits
    j = (int)x;
    if(j > 32767) j = 32767;
    else if(j < -32768) j = -32768;
*/

    if(flag) {
        j = k + (j << 16);
        flag = 0;

/* write 2 consecutive samples into FIFO (circular buffer) */ 
        asm volatile("bit set mode1 0x10; nop;
            dm(i1,m1) = %1;
            %0 = i1;
            bit clr mode1 0x10;  nop;" : "=d" (pin) : "d" (j));

/* keep checking the out pointer until pout gets close to pin */
/* do only while interups are enabled */
        if(int_flag) {
/* determine number of samples in FIFO and 
take care of circular buffer problems */
            do {
              asm volatile("bit set mode1 0x10; nop; \
                r0 = i0;                  /* -out pointer */
                r0 = -r0, i2 = i1;        /* in pointer */
                m2 = r0;
                modify(i2,m2);            /* in-out */
                %0 = i2;
                bit clr mode1 0x10;  nop;" : "=d" (pout) : );
            } while(pout > (FIFO_LENGTH - FIFO_LENGTH/8));
/* after the fifo empties some we get here */
        }
        else {
            if(pin > ((int)play_fifo + FIFO_LENGTH - FIFO_LENGTH/32)) int_enable();
        }
    }
    else {
        k = j & 0xffff;
        flag = 1;
    }
}

/* flush all samples out of the FIFO and then disable interrupts */

void flush()
{
    int pin,pout;
    int j;
    float sample,delta;

    asm("bit set mode1 0x10; nop; \
        %0 = i1; \
        bit clr mode1 0x10;  nop;" : "=d" (pin) : );

    if(pin == (int)play_fifo) pin = (int)play_fifo+FIFO_LENGTH-1; else pin--;

/* slowly drop the output to zero to avoid pop */
    j = *((int *)pin);
    j = j >> 16;
    delta = abs(j)/5000;
    if(delta <= 1.0) delta = 1.0;
    if(j > 0) {
        sample = (float)j;
        while(sample > 0.0) {
            sendout(sample);
            sample -= delta;
        }
    }
    else {
        sample = (float)j;
        while(sample < 0.0) {
            sendout(sample);
            sample += delta;
        }
    }

    if(!int_flag) int_enable();

    asm("bit set mode1 0x10; nop; \
        %0 = i1; \
        bit clr mode1 0x10;  nop;" : "=d" (pin) : );

    if(pin == (int)play_fifo) pin = (int)play_fifo +FIFO_LENGTH-1; else pin--;

/* wait for end of samples */
    do {
      asm volatile("bit set mode1 0x10; nop; \
        %0 = i0; \
        bit clr mode1 0x10;  nop;" : "=d" (pout) : );
    } while(pout != pin);

    int_disable();
}

/* interrupt enable function */

void int_enable()
{
/* enable real-time interrupts after clearing all pending interrupts */
asm("irptl = 0;
    bit set mode1 0x00001000; ");
    int_flag = 1;
}

/* interrupt disable function - disable all interrupts */

void int_disable()
{
/* disable real-time interrupts after clearing all pending interrupts,
reset pointers to circular buffers */
asm("   bit clr mode1 0x00001000; \
        bit set mode1 0x10;       \
        nop; \
        bit clr mode1 0x10;");
    int_flag = 0;

}