Вот наткнулся на готовый MP3 плеер
Supply Voltage:5V
Current:1000mA
CPU:Atmega 328P
MP3 Chip:VS1003
Interface:I2C/UART
UART:19200/8/N/1 (TTL level)
I2C Address:0x35
Output Power:2x3W
Support Media:MP3,WAV,MIDI
Support Meida Card: 1 GB Micro Card
Support command: Pause/Next Sound/Previoud Sound/Play Sound/ Volume Control