1. EE332 Junior Project Sound Recorder Spring 2001 Chris Brophy Matt Olinger Instructor: S. D. Gutschlag 4/26/01

2. Block Diagram Top Down Design Sample input audio Store in memory (Emac board) Play audio output

4. Audio Input Amplify microphone input Shift and Clip to protect A/D converter Sample input with software

5. Microphone PreAmp Basic Op-Amp with feedback for simplicity Easily adjustable offset for A/D

6. A/D Clipper Circuit ©2001 Brophy and Olinger

8. Software For sampling, used Timer 0 Interrupt For REC/PLAY/STOP buttons, used EXT3,5,6 For LEDs, used P1.6 and P1.7

9. Software Sample Rate Adjustable with T0 Set to 6kHz for human voice Maximum necessary frequency is 3kHz Double for Nyquist Theorem 32KB of memory Recording time of 5.3 seconds

11. Square Wave Memory Dump Sine Wave Memory Dump

12. Audio Output “Unshift” Output of D/A Amplify Output on speaker

13. Audio Output Preliminary Speaker Amplifier

14. Audio Output Final Speaker Amplifier

15. FFT Due to sampling effect of A/D, results are similar to the PAM lab. Aliasing effect is also seen past the Nyquist Theory frequency limit.

19. Conclusions and Performance Audio Samples Test at 3.6kHz Sample Rate Test at 5.9kHz Sample Rate Test at 16.4kHz Sample Rate All objectives were achieved: Microphone input Record into memory Output through speaker