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Abstract

Compressing raw audio with the MP3 standard can reduce the storage space required by

approximately one twelfth. [17] This has made it possible to play audio from devices

with limited storage space, for example mobile phones, PDA’s and flash based MP3

players. Their small size also makes them more convenient and flexible to use than

using traditional audio CDs. It is now possible to buy MP3 players that can play MP3s

from a CD containing ten or more albums or from a hard drive containing hundreds of

albums.

Another advantage of their small size is that they are very suitable for transferring

between devices, whether it be through USB, cable based networks or wireless

networks. This allows for the MP3s to be played in a remote location from where they

are stored. For a long time now people have been doing this on computers to play MP3s

that are stored on other computers connected via a LAN or the internet. Up until now

this has been limited to computers. The aim of this thesis is to produce a MP3 player

that can play MP3s that are stored on computers connected to it through a LAN or

internet connection. This enables the user to be able to play MP3s that are stored on

computers without being in the same environment as the computer.

The project was broken into two parts: development of an embedded MP3 decoder with

a network interface, and a server program on a PC to communicate to the player and

Windows. The networking on the player was performed using an Ethernut development

board. The Ethernut is an open source hardware and software project. The hardware

uses an Amel ATmega103 processor with a Realtek 8019 network controller and the

software is the Nut OS, which is a real-time operating system and Nut Net, which

provides networking APIs and a fully featured TCP/IP stack. The software developed

on the player streams the MP3 data from the server program on the PC through a TCP

connection. The server program determines which MP3 to stream by reading a standard

Winamp play list file. From this file it also determines the song title and sends it to the

player which receives the song name and displays it on an LCD. On the player the MP3

stream is received and stored in a buffer which in turn is sent to the MP3 decoder, the

VS1001k. Whenever the decoder needs more data it raises an interrupt and the program

feeds it data through a serial interface. A user is able to control how the music is played

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Motorola simplefi Especificaciones Pagina 2