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.

We adapted the design for our circuit from the schematic given on the PJRC website. The schematic for our circuit can be viewed here. Since the STA013 and the CS4334 were surface-mount chips, both chips required DIP adapters to connect to a breadboard. We used the Aries Electronics 32-650000-10 and the Capital Advanced Technologies 9082 for the STA013 and CS4334, respectively.

In order to improve the quality of the output of the DAC (i.e., eliminate noise, etc.), both the left and right outputs were filtered using a band-pass filter. In addition, an inductor was placed in series with the 5 volt supply rail for the DAC in order to eliminate noise due to other circuitry.

Hard-Drive Circuity:

The hard-drive was driven by a 5 volt and a 12 volt power supply. Since the hard-drive used 5 volts for a logic high, while the Atmel Mega103L used 3 volts as a logic high, we needed to implement a bi-directional voltage level shifter. To do this, we implemented the design from the PJRC website which used two resistors to change a 5 volt logic high to a 3 volt logic high. No level shifting had to be done from 3 volts to 5 volts because the built in transistors on the hard-drive have a logic high region ranging from 5 volts to below 3 volts. The schematic for the hard-drive interface can be seen here.

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