echo.c

基本回音程式,可以改变parameter来测试其速度和音响。

#include "audio.h"
#include "dipled.h"

#include <stdio.h>
#include <csl.h>
#include <csl_mcbsp.h>

/* Configurations for the control and data interface (audio.c) */
extern MCBSP_Config audioCntlCfg;
extern MCBSP_Config audioDataCfg;
/* AIC23 configuration (audio.c) */
extern CODEC_Config codecCfg;

/* Handles to the McBSP ports (audio.c) */
extern MCBSP_Handle hAudio_cntl;
extern MCBSP_Handle hAudio_data;


#define bufferlength  3000		     //buffer size for delay
#pragma DATA_SECTION(left_buffer, ".buffer");
#pragma DATA_SECTION(right_buffer, ".buffer");

short left_buffer[bufferlength];			     //create buffer
short right_buffer[bufferlength];			     //create buffer
short i = 0;
short amplitude = 5;			     //to vary amplitude of echo 


/* configure the codec to operate at 8KHz samp. rate */
void audio_setFreq_8k(void)
{
	codecCfg.regs[8] &= ~0x003e; /* mask SR3..SR0 & BOSR */
	codecCfg.regs[8] |= 0x000d;
	audio_reset();
}

/*Joshuatok*/
void main(void)
{
	Int16 left_in, right_in;
	Int16 left_out, right_out;

	printf("Echo\n");
	
	CSL_init();  /* initialize CSL, required! */

	audio_setup();	/* configure the audio interface */
	audio_start();	/* start the receive and transmit of samples */
	
   audio_setFreq_8k();

	for (i=0; i<bufferlength; i++){
		left_buffer[i] = 0;
		right_buffer[i] = 0;
	}
   
    i = 0;
	 while(1){

       	while(!MCBSP_rrdy(hAudio_data));
		left_in = MCBSP_read16(hAudio_data);
  		while(!MCBSP_rrdy(hAudio_data));		
		right_in = MCBSP_read16(hAudio_data);	
		
		left_out  = left_in  + 0.1*amplitude*left_buffer[i];
		right_out = right_in + 0.1*amplitude*right_buffer[i];

		/* replace the oldest sample */
		//left_buffer[i] = left_in;
		left_buffer[i] = left_out;
		//right_buffer[i] = right_in;
		right_buffer[i] = right_out;

		i++;
		if (i>=bufferlength){
			i = 0;
		}
		      
       	while(!MCBSP_xrdy(hAudio_data));
		MCBSP_write16(hAudio_data, left_out);
  		while(!MCBSP_xrdy(hAudio_data));		
		MCBSP_write16(hAudio_data, right_out);		
	}
}

/*Joshuatok*/