Low Power FM Receiver Andrew Young November 17, 2008

Overview Project Inspiration Requirements Differences Design Block Diagram Design Schematic Operational Flowchart LCD Layout Questions

Inspiration 2008 IEEE Student Contest Senior Design Project Objective: Create low power FM radio receiver Can use commercially-available IC subsystems Senior Design Project Competition between two teams Goal is lowest power consumption 3

Design Requirements Receive FM radio from 88.1 to 107.9 MHz Output audio at > 4mW per channel to standard 32-Ohm headphones (33-Ohm resistors used for testing) Adjustable volume/station Interact with user via LCD interface Entire design implemented on one PCB Competition Testing: One supply source, < 15V DC Design allows for internal circuit inspection Optional Extras: Display RDS data (station name, artist, song title) Any extra features (signal strength, station presets, menu) My own customization – video games, easter eggs, etc.

Differences What is different about this design compared to the senior design project? Extra features – Something cool to add which takes advantage of already-existing components, such as the attached LCD and joystick (video game, perhaps?).

Design Block Diagram Headphone Amplifier FM Receiver IC (Si4703) Microcontroller (ATMega32) LCD/User Interface 104.1 6

Schematic - Page 1 Push Buttons LCD FM Receiver Voltage Adjustment Port A LCD FM Receiver Port B Audio L/R Si4703 Comm Voltage Adjustment ATMega32 Battery Output Switching Power Supply

Schematic - Page 2 Batteries (2x AA) Clock Generator Headphone Jack On/Off Switch Batteries (2x AA) Clock Generator Headphone Jack Gain Adjustment Potentiometers Noise Suppression Audio L/R Input Coupling ESD Protection Low Voltage Input Audio Amplifier

AVR Application Development Codevision AVR IDE (Evaluation) Limited to 2kB code size Built-in libraries (LCD, I2C, Power-Save) AVR Studio 4.0 Used to debug and set clock rates, voltage levels, fuses

Operational Flowchart Power on Interrupt When Button Pressed AVR Initializes Receiver & LCD Determine Button Pressed (Volume Up or Down, Tune Up or Down) Set to Default Station & Volume Send Appropriate Signal to IC to Change Volume/Station Idle Receive RDS Data Send Appropriate Signal to Receive Current Volume/Station Receive Signal Strength Translate Data to LCD Output Output Signal & RDS to LCD Interrupt Return from Interrupt

LCD Layout 104.1 - KZRZ Artist – Song Name Sig. █ █ █ █ Vol. █ █ █ █ █ █ █ █ █

Summary Designing Low-Power FM Radio Receiver w/ Inspiration: Senior Design Competition Extras: Features not required by the senior design project, such as a video game using the 4x20 LCD and the attached joystick. 12

Questions

ATMega32 AVR

Silicon Labs Si4703

Headphone Amplifier – MAX9725