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Digital Audio Sound System

Digital Audio Sound System. ECE 345 – Senior Design Chris Gouveia Lawrence Lau December 4, 2003. Overview. Background Goals Initial Design Design Decisions Challenges Final Design Testing Final Analysis. Typical Sound System. Our Digital Sound System. Transmitter. Receiver.

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Digital Audio Sound System

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  1. Digital Audio Sound System ECE 345 – Senior Design Chris Gouveia Lawrence Lau December 4, 2003

  2. Overview • Background • Goals • Initial Design • Design Decisions • Challenges • Final Design • Testing • Final Analysis ECE 345 Senior Design - Gouveia, Lau

  3. Typical Sound System ECE 345 Senior Design - Gouveia, Lau

  4. Our Digital Sound System Transmitter Receiver ECE 345 Senior Design - Gouveia, Lau

  5. Our Digital Sound System • Project Benefits • Eliminates long cable runs • Minimizes cable clutter • Reduces cost • Reduces noise • Lowers the number of fault points • Simplifies system installation • Allows system to be upgraded to a digital one easily ECE 345 Senior Design - Gouveia, Lau

  6. Our Digital Sound System • Transmitter • Input analog sound from source • Convert audio to digital format • Output Ethernet packets onto network • Receiver • Input Ethernet packets from network • Convert audio to analog format • Amplify output • Output analog audio to destination ECE 345 Senior Design - Gouveia, Lau

  7. Goals • 96kHz, 24 bit sampling • Stereo signaling • High fidelity • Minimal delay ECE 345 Senior Design - Gouveia, Lau

  8. Design Process • Start from the ends • Analog to Digital converter needed • Digital to Analog converter needed • Network processors in the middle • Microcontroller or microprocessor controlled • Glue logic ECE 345 Senior Design - Gouveia, Lau

  9. Functional Diagram Process Analog Signal A/D Conversion Collect Several Samples Create Network Packet Pass to Ethernet Controller Transmit Amplify Signal D/A Conversion Buffer Samples for D/A Decode Network Packet Pass to Controller Receive ECE 345 Senior Design - Gouveia, Lau

  10. Block Diagram Transmitter Sound Source Analog Circuitry Analog to Digital Converter Controller Ethernet Controller/PHY Speaker Analog Circuitry Digital to Analog Converter Controller Ethernet Controller/PHY Receiver ECE 345 Senior Design - Gouveia, Lau

  11. Initial Analysis • Digital audio data rate ECE 345 Senior Design - Gouveia, Lau

  12. Initial Analysis • Digital audio sampling rate ECE 345 Senior Design - Gouveia, Lau

  13. Initial Analysis • Digital audio buffering rate ECE 345 Senior Design - Gouveia, Lau

  14. Performance Requirements • 96 kHz sampling • 24 bit fidelity • Less than 5% harmonic distortion • 15ms maximum delay ECE 345 Senior Design - Gouveia, Lau

  15. Design Decisions • Analog and Digital Converters • Sampling rate • Bit depth • Interface • Microcontroller • Clock speed • Memory • Ethernet capabilities ECE 345 Senior Design - Gouveia, Lau

  16. Design Decisions • Microcontroller • Motorola Coldfire 5282 Microcontroller • Analog to Digital Converter • Texas Instruments PCM1804 • Digital to Analog Converter • Texas Instruments PCM1716 • Amplifier • National Instruments LM4832 ECE 345 Senior Design - Gouveia, Lau

  17. Challenges • Microcontroller operating system • Documentation • Microcontroller I/O • Crystal Oscillator • Power ECE 345 Senior Design - Gouveia, Lau

  18. Challenges • Microcontroller operating system • Scheduling algorithm • Slightly limited feature set ECE 345 Senior Design - Gouveia, Lau

  19. Challenges • Documentation • Poor documentation of system functions and examples • Made coding difficult • Required digging down into system code to understand functionality ECE 345 Senior Design - Gouveia, Lau

  20. Challenges • Microcontroller I/O • Minimum of 24 I/O pins required • Not enough general purpose I/O pins • Data bus requires protocol • No daughter processor to perform protocol with microcontroller ECE 345 Senior Design - Gouveia, Lau

  21. Challenges • Crystal oscillator • Unable to provide clean and stable clock source • Dirtied power and ground planes ECE 345 Senior Design - Gouveia, Lau

  22. Challenges • Power ECE 345 Senior Design - Gouveia, Lau

  23. Final Design Transmitter Analog Circuitry Analog to Digital Converter Sound Source Speaker Amplifier Digital to Analog Converter Controller Receiver ECE 345 Senior Design - Gouveia, Lau

  24. Final Design • Successes • Microcontrollers communicated via UDP • A/D and D/A transmitted audio • Microcontroller controlled D/A and amplifier • Failures • Transmit audio data using microcontrollers ECE 345 Senior Design - Gouveia, Lau

  25. Testing • Spectrum analysis • Signal to Noise Ratio • Total Harmonic Distortion ECE 345 Senior Design - Gouveia, Lau

  26. Testing • Spectrum analysis • 10 second sound sample • 1kHz tone • 10kHz tone ECE 345 Senior Design - Gouveia, Lau

  27. Testing • Spectrum analysis • 10 second sound sample • Dave Matthews Band – Crash Into Me • MP3 encoded • Captured using a consumer sound card • Control sample – Blue • Sample through system - Red ECE 345 Senior Design - Gouveia, Lau

  28. Testing ECE 345 Senior Design - Gouveia, Lau

  29. Testing • Spectrum analysis • 1 kHz tone • Generated by function generator • Captured using a consumer sound card • Control sample – Red • Sample through system - Blue ECE 345 Senior Design - Gouveia, Lau

  30. Testing ECE 345 Senior Design - Gouveia, Lau

  31. Testing • Spectrum analysis • 10 kHz tone • Generated by function generator • Captured using a consumer sound card • Control sample – Red • Sample through system - Blue ECE 345 Senior Design - Gouveia, Lau

  32. Testing ECE 345 Senior Design - Gouveia, Lau

  33. Testing • Signal to Noise Ratio • SNR is 45.5 dB • Affected by high noise floor • Determined using Distortion Analyzer and a 1kHz test tone ECE 345 Senior Design - Gouveia, Lau

  34. Testing • Total Harmonic Distortion • Measured using Distortion Analyzer • Sinusoid generated by function generator • Output fed through commercial mixer to generate differential output required by Distortion Analyzer ECE 345 Senior Design - Gouveia, Lau

  35. Testing ECE 345 Senior Design - Gouveia, Lau

  36. Final Analysis • If we had one more month: • Use an FPGA to offload data gathering from microcontroller • Let microcontroller only send network traffic • Use a clock buffer and PLL to provide stable clock source • Use separate logic and analog power sources • Develop cleaner power regulation ECE 345 Senior Design - Gouveia, Lau

  37. Questions ? ECE 345 Senior Design - Gouveia, Lau

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