This project detects a voice signal from a microphone, then plays it back in the reverse direction using DSP Starter Kit (DSK). This was done at IIT Patna.

1. Voice Detection and
Reverse Playback
By
Jeevan Prakash
Mtech-1311EE05

2. Contents
• Aim of the project
• Requirements for the project
• Hardware
• software
• Theory
• Conclusion
• References

3. Aim
• This project detects a voice signal from a
microphone, then plays it back in the reverse
direction using DSP Starter Kit (DSK).
Microphone
DSP Starter
Kit
Speaker

4. DSK Support tools
1.DSP Starter Kit package includes:
(a) Code composer studio v3.1(Software)
(b) A board TMS320C6713-16 bit stereo
codec
(c) A USB cable that connects the DSK board
to the PC
(d) A 5v power supply for the DSK board
2. PC
3.Microphone and headphones/speaker

5. Connections

6. Board

7. Block diagram

8. Code Composer Studio v3.1
• Code Composer is the DSP industry's first fully integrated
development environment (IDE) with DSP-specific
functionality.
• It can Edit, build, debug, profile and manage projects from a
single unified environment.
• Unique features include
• Code generation such as a C compiler, an assembler, and a linker.
• Graphical capabilities
• Supports real-time debugging.
• An easy-to-use software tool to build and debug programs.

9. Software Tool Flow
.c .asm .obj .out
• The C compiler compiles a C source program with extension .c
to produce an assembly source file with extension .asm.
• The assembler assembles an .asm source file to produce a
machine language object file with extension .obj.
• The linker combines object files and object libraries as input to
produce an executable file with extension .out.
• This executable file can be loaded and run directly on the
C6713 processor.
Text Editor Compiler Assembler linker

10. Theory
Fig: Block Diagram for the detection of a voice signal from
a microphone and playback of that signal in the reverse direction
Block diagram:

11. Cont…
• Two circular buffers are used:
• An input buffer to hold 80,000 samples (10 seconds of data)
continuously being updated.
• An output buffer to play back the input voice signal in the reverse
direction.
• The signal level is monitored, and its envelope is tracked to
determine whether or not a voice signal is present.
• When a voice signal appears and subsequently dies out, the
signal - level monitor sends a command to start the playback
of the accumulated voice signal, specifying the duration of the
signal in samples.

12. Cont…
• The stored data are transferred from the input buffer to the
output buffer for playback.
• Playback stops when one reaches the end of the entire signal
detected.
Signal Level Monitor:
• It includes rectification and filtering (using a simple first order
IIR filter).

13. Cont…
DC Blocking first order IIR High pass filter:

14. Conclusions
• We can detect voice and playback it reversely using DSP
kit.
• Here we are learning code composer studio software.
• Here we are using TMS320C6713 dsp kit also.

15. References
• Digital Signal Processing and Applications with the
TMS320C6713 and TMS320C6416 DSK by
Rulph Chassaing and Donald Reay.