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Digital Audio Recorder the unexpected journey

Digital Audio Recorder the unexpected journey. by John Klempir and Jason Tang ECE 345 Senior Design TA: Jeff Cook 11/29/2000. Why Digital?. Digital recordings can be ->……………. Higher quality More reproducible Stored with virtually no degradation Used in smaller hand-held devices

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Digital Audio Recorder the unexpected journey

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  1. Digital Audio Recorderthe unexpected journey by John Klempir and Jason Tang ECE 345 Senior Design TA: Jeff Cook 11/29/2000

  2. Why Digital? • Digital recordings can be ->……………. • Higher quality • More reproducible • Stored with virtually no degradation • Used in smaller hand-held devices • Produced with fewer mechanical parts

  3. Basic Digital Recorder Flow Diagram Analog to Digital Converter Digital to Analog Converter Left Microphone Storage Device Left Speaker Analog to Digital Converter Digital to Analog Converter Right Microphone Right Speaker

  4. Original Design • Digital audio device implementation • Crystal CODEC - performs A/D and D/A, filtering, level setting, 4 audio inputs, L/R output • Panasonic Electret Microphone - small package condenser type; designed for hand held devices • Advanced Micro Devices flash RAM - 4 Mbit capacity; sufficient for brief sampling • Motorola HC12 microcontroller - brains of unit

  5. CODEC-based product features • User friendly interface - Play, Stop, and Record. • Microphone input for voice capture. • Speaker/Headphone output. • 16-bit recording quality. • 22k samples per second. • Extended playing time. • Tapeless recording.

  6. Power Supply HC12 flash RAM CODEC Microphone Speaker Initial Design

  7. Design Review • Schematics with detailed pin assignments provided. • Software flowchart/diagram was also presented utilizing the CODEC based design. • Began to solder, assemble, and wire up.

  8. Soldered, wired, and surfboard mounted CODEC

  9. CDB4215 Evaluation Board from Crystal Semiconductor

  10. Problems, Problems, Problems • AMD distribution problems. • Sought assistance from Professor Swenson. • Asked for help from TA Jeff Cook.

  11. CODEC Memory We needed a new design and/or new parts. • Search for alternative memory distributors, brands, and formats. • We decided to go with a chip with CODEC capabilities and on board memory capacity.

  12. ISD 2532 ISD 2532 Stereo Recording Design • ISD2532 chip • Dual chips used for stereo recording • Single set of control buttons, PLAY, STOP, PAUSE, and RECORD. • Left and Right speaker outputs.

  13. Speaker and Headphone compatibility • Packard Bell powered computer speakers, volume control. • HQ walkman speakers, no power, no volume control. • Sony walkman headphones, no volume control. • British Airways headphones, no vol control.

  14. Microcontroller Control • Three modes of operation • Play • Continues until stop, pause or record is pressed • Monitors chip to detect when end of message is reached • Record • Continues until stop, pause, or play is pressed • Monitors chip to detect when chip is full • Idle • Waits until play or record is pressed • Pause sub-mode for Play and Record • Scan user inputs until play or record is pressed

  15. Testing • Verify that a recording of a musical note would be played back at its original frequency • Used a properly tuned guitar to generate a note • A guitar tuner checked the output of the speakers by display the note registered

  16. Future Improvements • Multiple recordings. • LED panel displays for titles and times. • PCB design and mobile hand held capacity. • Larger recording capacity.

  17. Active listeners demand mobile solutions to their listening needs. Hand held mobile devices are growing in popularity. This device could be feasibly manufactured. Marketed toward teens who like hand held gadgets. Also marketed toward the “personal notepad” products. Consumer Design Possibilities

  18. Questions?

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