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

	File:        irr.c

	Description: Perform 1-stage and 4-stage quad IIR filter and output 

		     to left and right channel of line-out respectively.

		     * Note: cutoff of single stage is 6 kHz @ 20 kHz.

	

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



#include <stdio.h>

#include <string.h>

#include <common.h>

#include <codec.h>

#include <mcbspdrv.h>

#include <board.h>

#include <stdlib.h>

#include <timer.h>

#include <intr.h>

#include <regs.h>



#define SAMPLING_RATE 20000



extern int inicodec (int sampling_rate);



#pragma CODE_SECTION(isr_rint0,".iprog") 



interrupt void isr_rint0 (void)

{

	short a1 = 0xd0b4;   // Negative value of a1

	short a2 = 0xe6f0;   // Negative value of a2



	short b0 = 0x3217;

	short b1 = 0x642e;

	short b2  = 0x3217;

	static short d01=0, d02=0, d00;

	static short d11=0, d12=0, d10;

	static short d21=0, d22=0, d20;

	static short d31=0, d32=0, d30;

	short xn, y0, y1, y2, y3;

	int prod1, prod2, prod3, prod4, prod5;

	int sin, sout;



	//============= pre filter =============

	sin = MCBSP0_DRR;

	//============= stage 0 =============

	xn = (short) (sin & 0x000ffff);

	prod1 = _mpy(d02,a2)>>15;

	prod2 = _mpy(d01,a1)>>15;

	d00 = xn + (short)(prod1 + prod2);

	prod3 = _mpy(d01,b1);

	prod4 = _mpy(d02,b2);

	prod5 = _mpy(d00,b0);

	y0 = (short)((prod3+prod4+prod5)>>15);

	d02 = d01;

	d01 = d00;

	//============= stage 1 =============

	prod1 = _mpy(d12,a2)>>15;

	prod2 = _mpy(d11,a1)>>15;

	d10 = y0 + (short)(prod1 + prod2);

	prod3 = _mpy(d11,b1);

	prod4 = _mpy(d12,b2);

	prod5 = _mpy(d10,b0);

	y1 = (short)((prod3+prod4+prod5)>>15);

	d12 = d11;

	d11 = d10;

	//============= stage 2 =============

	prod1 = _mpy(d22,a2)>>15;

	prod2 = _mpy(d21,a1)>>15;

	d20 = y1 + (short)(prod1 + prod2);

	prod3 = _mpy(d21,b1);

	prod4 = _mpy(d22,b2);

	prod5 = _mpy(d20,b0);

	y2 = (short)((prod3+prod4+prod5)>>15);

	d22 = d21;

	d21 = d20;

	//============= stage 3 =============

	prod1 = _mpy(d32,a2)>>15;

	prod2 = _mpy(d31,a1)>>15;

	d30 = y2 + (short)(prod1 + prod2);

	prod3 = _mpy(d31,b1);

	prod4 = _mpy(d32,b2);

	prod5 = _mpy(d30,b0);

	y3 = (short)((prod3+prod4+prod5)>>15);

	d32 = d31;

	d31 = d30;

	//============= post filter =============

	sout = (((int)y3)<<16)|(((int)y0)&0xffff);

	MCBSP0_DXR = sout;

	

	return;

}



void Init_Interrupts ()

{

	intr_reset();                     // Reset the interrupt system,

					  // disable all interrupts.

	INTR_CLR_FLAG (CPU_INT15);        // Clear previous interrupt request

	INTR_ENABLE (CPU_INT15);          // Enable cpu interrupt line 15

	intr_map(CPU_INT15,ISN_RINT0);    // Link receive interrupt of serial

					  // port 0 to interrupt line 15.

	intr_hook (isr_rint0,CPU_INT15);  // Assign the interrupt service routine

}



void main(void)

{

	evm_init();                        // Initialise EVM board.

	inicodec (SAMPLING_RATE);         // Initialise codec, adjust sampling rate.

	Init_Interrupts ();               // Initialise interrupts and hook isr.

	INTR_GLOBAL_ENABLE();             // Enable global interrupt.



	for (;;);                         // Main loop, does nothing.

}