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USB FM RADIO

Introduction
This USB FM Radio design is intended as a reference for incorporating FM radio functionality into a USB product. The design consists of two major components, the Si4701 FM radio receiver and the C8051F321 microcontroller with a built-in universal serial bus (USB) peripheral. Due to the high level of system integration of both of these components, the total design is very small with fewer external components than many other solutions. The software, firmware, schematic, and layout source for this design are located in AN264SW.zip. The latest version of these files as well as this document itself can be found at the following URL: http://silabsusbradio 2. System Overview The system consists of a Windows® application that communicates with the C8051F321 using the USB connection. The C8051F321 microcontroller controls the Si4701 using the serial peripheral interface (SPI). The Si4701 audio outputs are sampled using the C8051F321’s analog-to-digital converter (ADC) and sent to the host across the USB interface. The Windows application plays the audio using the PC speakers or headphones.