LMS Algorithm for noise cancelling

Hi!

I'm trying to develop an ANC system using the LMS filter. I'm using NIOSII processor and the altera Audio UP IP core. Simulating the algorithm in Matlab, it works very well, but when i code it in C I cannot achieve any result. I think the problem is related to the use of integer instead of float. Probably some shift operations are wrong but i can't find the error. I post both the C code and Matlab code.

Thanks!

Matlab Code:

close all
%clear all
w0 = 0;
w1 = 0;
w2 = 0;
w3 = 0;
u0 = 0;
u1 = 0;
u2 = 0;
u3 = 0;
load song
iterations = 500000;
%song = wavread('C:\Users\Dan\Desktop\a.wav',500000);
s = 0.5*song;
n = 0.3*(rand(1,size(s))-0.5);
n_f = filter(,1,n);
x = transpose(s)+n_f;
mu = 0.001;
for i=1:iterations,
    y = x(i);
    u3 = n(i);
    yf = w0*u3 + w1*u2 + w2*u1 + w3*u0;
    e(i) = y-yf;
    w0 = w0 + mu*e(i)*sign(u3);
    w1 = w1 + mu*e(i)*sign(u2);
    w2 = w2 + mu*e(i)*sign(u1);
    w3 = w3 + mu*e(i)*sign(u0);
    u0=u1;
    u1=u2;
    u2=u3;
end
wavplay(e',44100);
    

C Code:

#include "sys/alt_stdio.h"
# include "altera_up_avalon_audio.h"
# include "altera_avalon_pio_regs.h"
# define LENGHT 10
int main(void){
	alt_putstr("Hello from Nios II! audio TEST\n");
	alt_up_audio_dev * audio_dev;
	int * sw_ptr = (int *) 0x01101020; // sw address
	int l_buf,r_buf,mono_data;
	int sw;
	int u, w;
	int y, e;
	int mu = 214;
	int m,temp;
	// open the Audio port
	audio_dev = alt_up_audio_open_dev ("/dev/audio_0");
	if ( audio_dev == NULL)
		alt_printf ("Error: could not open audio device \n");
	else
		alt_printf ("Opened audio device \n");
	for(m=0;m<LENGHT;m++){
		w=0;
		u=0;
	}
	/* read and filter audio data */
	while(1)
	{
		int fifospace = alt_up_audio_read_fifo_avail (audio_dev, ALT_UP_AUDIO_RIGHT);
//		IOWR_ALTERA_AVALON_PIO_DATA(LEDR_BASE, fifospace);
//		// demo swithes and leds
//		sw=IORD_ALTERA_AVALON_PIO_DATA(SWITCHES_BASE);
//		IOWR_ALTERA_AVALON_PIO_DATA(LEDG_BASE, sw);
		if ( fifospace > 15 ) // check if data is available
		{
			// read audio buffer
			alt_up_audio_read_fifo (audio_dev, &(r_buf), 1, ALT_UP_AUDIO_RIGHT);//Suono + rumore
			alt_up_audio_read_fifo (audio_dev, &(l_buf), 1, ALT_UP_AUDIO_LEFT);//Rumore
			if(*sw_ptr == 1){
				u = l_buf;
				y = 0;
				for(m=0;m<LENGHT;m++){
					y += (int)(((long)(w*(u)))>>15);
				}
				e = r_buf - y;//Segnale errore (stima)
				alt_up_audio_write_fifo (audio_dev, &(e), 1, ALT_UP_AUDIO_RIGHT);
				alt_up_audio_write_fifo (audio_dev, &(e), 1, ALT_UP_AUDIO_LEFT);
				temp = (int)(((long)(mu*e))>>15);
				for(m=0;m<LENGHT;m++){
					w=(w + (int)((long)(u*temp))>>15);
				}
				for(m=0;m<LENGHT-1;m++){
					u = u;
				}
			}
			else{
				alt_up_audio_write_fifo (audio_dev, &(r_buf), 1, ALT_UP_AUDIO_RIGHT);
				alt_up_audio_write_fifo (audio_dev, &(l_buf), 1, ALT_UP_AUDIO_LEFT);
			}
		}
	}
	return 0;
}