Summary of MP3 Player Using Atmel Mega103L
This project describes the design of a portable MP3 player circuit using an 8-bit microcontroller to decode MP3 files and convert them to analog audio. The team utilized an STA013 decoder chip and a CS4334 DAC, controlled by an Atmel Mega103L microcontroller running at 3 Volts. Although they successfully implemented the decoding circuit, time constraints prevented the completion of software drivers for the added hard-drive interface intended to store MP3 files.
Parts used in the MP3 Player:
- STA013 MP3 Decoder Chip
- Aries Electronics 32-650000-10 Dip Adaptor
- 14.7456 MHz Crystal
- CS4334 24-bit Digital-to-Analog Converter
- Advanced Technologies 9082 Surf Board
- Atmel Mega103L Microcontroller
- STK300 Development Board
- Bench Power Supply
- Amplified Computer Speakers
- 1/8 Stereo Jack
- 340 MByte Hard-Drive
- IDE Cable
- 2 Breadboards
- Resistors (270 Ohm, 4.7 K Ohm, 4.7 Ohm, 560 Ohm, 1 K Ohm, 1 M Ohm)
- Inductor (100 µH)
- Capacitors (0.1 µF, 34 pF, 10 µF, 3.3 µF, 3.3 nF, 470 pF, 4.7 nF)
- Wire
Introduction
Using MPEG Layer-3 compression, 40 MByte audio files have been compressed to approximately 3.5 MBytes. With the wide availability of MP3 files via the Internet, portable MP3 players have become increasingly popular. MP3 players are currently available that utilize either Compact Discs, SmartMedia, Compact Flash, or a hard-drive as their storage medium.
Our interest in MP3 technology led us to design a circuit that would convert an MP3 file into an audio signal for our final project. The circuit utilizes an MP3 decoder chip to convert an MP3 file into a digital signal. The resulting digital signal is then converted to an analog audio signal via a Digital-to-Analog Converter (DAC). An 8-bit Microcontroller controls the flow of data to the MP3 decoder chip.
Since we finished the MP3 decoding circuit ahead of schedule, we decided to additionally implement a hard-drive interface to store the MP3 files. Once again, an 8-bit Microcontroller controlled all data transfers to and from the hard-drive. Due to time limitations, we were not able to finish the software drivers for this circuit.
Hardware
MP3 Decoder Circuity:
For our original design, we intended to use the VS1001 MP3 decoder chip. Due to the amount of time required to obtain the VS1001 MP3 decoder chip, we decided to change our design to use the STA013 MP3 decoder chip clocked at 14.7456 MHz. We also chose to use the CS4334 24-bit DAC, as the STA013 is capable of generating all control signals for it.
As the STA013 is a 3 Volt chip, we chose to use the Atmel Mega103L Microcontroller which is also a 3 Volt chip. This eliminated the need for any level shifting of signals between the STA013 and the Atmel Mega103L. The additional flash memory (128K in total) on the Atmel Mega103L also allowed us to store a short MP3 clip on the MCU in order to test the Atmel Mega103L/STA013 interface.
Parts List:
- STA013 MP3 Decoder Chip
- Aries Electronics 32-650000-10 Dip Adaptor
- 14.7456 MHz Crystal
- CS4334 24-bit Digital-to-Analog Converter
- Advanced Technologies 9082 Surf Board
- Atmel Mega103L
- STK300 Development Board
- Bench Power Supply
- Amplified Computer Speakers
- 1/8″ Stereo Jack
- 340 MByte Hard-Drive
- IDE Cable
- 2 Breadboards
- 16 x 270 Ohm Resistors
- 16 x 4.7 K Ohm Resistors
- 2 x 4.7 Ohm Resistors
- 2 x 560 Ohm Resistors
- 1 x 1 K Ohm Resistor
- 1 x 1 M Ohm Resistor
- 1 x 100 µH Inductor
- 6 x 0.1 µF Capacitors
- 2 x 34 pF Capacitors
- 1 x 10 µF Capacitor
- 2 x 3.3 µF Capacitors
- 2 x 3.3 nF Capacitors
- 1 x 470 pF Capacitor
- 1 x 4.7 nF Capacitor
- Wire
For more detail: EE 476 Final Project: MP3 Player
- What compression method allows large audio files to be reduced significantly?
MPEG Layer-3 compression is used to reduce 40 MByte audio files to approximately 3.5 MBytes. - How does the circuit convert an MP3 file into an audio signal?
An MP3 decoder chip converts the file into a digital signal, which is then converted to an analog audio signal via a Digital-to-Analog Converter. - Which microcontroller was chosen for the project and why?
The Atmel Mega103L was chosen because it is a 3 Volt chip, eliminating the need for level shifting with the STA013 decoder. - Can the STA013 generate control signals for the DAC?
Yes, the STA013 is capable of generating all control signals required for the CS4334 24-bit DAC. - What storage media options are currently available for MP3 players?
MP3 players are available that utilize Compact Discs, SmartMedia, Compact Flash, or a hard-drive as their storage medium. - Why did the team change from the VS1001 to the STA013 chip?
The team changed the design due to the amount of time required to obtain the VS1001 MP3 decoder chip. - Was the software driver for the hard-drive interface completed?
No, due to time limitations, the team was not able to finish the software drivers for the hard-drive interface. - What clock speed was used for the STA013 decoder chip?
The STA013 MP3 decoder chip was clocked at 14.7456 MHz.
