1. “TMS320C5505 USB Stick Teaching Materials”
Texas Instruments University Programme
Teaching Materials

2. Introduction

3. TMS320C5505 USB Stick A very low-cost $49 – student price
Microphone / line in and headphones out for learning audio Digital Signal Processing (DSP)
Upgrade path to C5515 ($75) and DSKs ($400).

4. About the TMS320C5505 The TMS320C5505 is a 16-bit fixed-point DSP
It has been optimised for low-power operation e.g. for battery operated portable devices.

5. Code Composer Studio (CCS)
Each TMS320C5505 USB Stick is provided with a CD containing Code Composer Studio Integrated Development Environment (IDE).

6. Using CCS With CCS you can: Write programs
Download programs to the hardware
Run the programs on the hardware
Debug the programs.

7. Teaching Materials

8. Teaching Material Consists of 20 hands-on audio applications
Focus is on practical experiments rather than pure theory
Fully functioning high-level C code provided for each application
Emphasis on real-time and low-power operation.

9. Target Audience This teaching material is aimed at beginners to DSP
It can be used either in class or for self-study
Some basic knowledge of C programming is required
As the lessons progress, more knowledge of DSP is required. It is therefore recommended that the student reads some of the material given in the reference sections.

10. Other Equipment Required
Microphone or output from MP4 player
Headphones or computer speakers
A frequency meter or multi-meter is useful.

11. Format of a Typical Application

12. Format of Each Application
Each of the 20 applications contain:
A Powerpoint presentation
A working C code example to run on the TMS320C5505 USB Stick
A brief outline of a typical application now follows.

13. Echo – Step 1 - Description
Echo is audible because the speed of sound is relatively slow, about 400 meters per second
Click on icon to listen to echo.

14. Echo – Step 2 - Block Diagram
Output = Input + Delayed Input
Because of losses in the delayed path, Gain < 1.

15. Echo – Step 3 – Derive Equation

16. Echo – Step 4 - Matlab Model
The frequency response of echo can be calculated using the following Matlab .m file.
Simulink models are used on many examples. For reverberation using the above .m file, simply interchange variables a and b.

17. Echo – Step 5 – System Response

18. Step 6 – C Code Full C code is provided for each application
Uses the Texas Instruments Code Support Library (CSL) to simplify the design process.

19. Echo – Step 7 – Run code on USB Stick
USB to PC
Microphone
Headphones

20. Echo – Step 8 – Experiments
How code can be improved and expanded on by the student
Main points and critical issues e.g. echo is always stable
How this simple principle can used in other more complex DSP applications. Echo is an example of a Finite Impulse Response (FIR) filter.

21. Echo – Step 9 - Questions Self-test questions on key points
Answers are to be found in the presentation.

22. Some Other Applications

23. Reverberation

24. Reverberation
Reverberation is similar to echo, but uses a slightly different configuration
Click on the icon to hear reverberation.

25. Reverberation on Stage
Sound reaches the microphone from both the performer and the the loudspeakers.

26. Reverberation Frequency Response

27. Important Points about Reverberation
The output is derived from both the input and the previous output
Can become unstable (the poles lie on the unit circle)
Reverberation is an example of an Infinite Impulse Response (IIR) filter.

28. Alien Voices

29. Alien Voices
Multiply audio input by a sine wave. This is known as “ring modulation”
Output contains sum and difference frequencies, but not those you started with
To listen to ring modulation, click on the icon below.

30. Waveforms of Ring Modulation

31. Dual Tone Multi Frequency Generation (DTMF)

32. Touch Pad Telephone
A standard touch pad phone generates the following tones:

33. Dual Tone Multi Frequency (DTMF)
Each tone in fact consists of pairs of defined single tones
Every time a button is pressed, a dual tone is generated.

34. Goertzel Algorithm

35. Piano Player with Perfect Pitch
If you sing a note, a musician with perfect pitch can tell you exactly what note you sang – “you sang the note B-flat”.

36. Goertzel Algorithm
The Goertzel Algorithm is the musician with perfect pitch in DSP form
It listens to the DTMF tones from the touch phone
Filters out pairs of individual tones
Determines which button was pressed.

37. Guitar Effects

38. Guitar Effects Can play an electric guitar through the USB Stick.
Enhance the sound using:
Fuzz
Valve / Tube sound
Reverberation
Flanging / Phasing

39. USB Stick Setup for Guitar
USB to PC
Headphones
Electric Guitar
The normal output from a guitar is a ¼” (6.25mm) jack plug. It will be necessary to use an adapter to 1/8” (3.5mm)

40. Adaptive Noise Reduction

41. Adaptive Noise Reduction
Used in headphones for pilots to remove aircraft noise
Based on Least Mean Squares (LMS) algorithm.

42. Graphic Equaliser Analogy
An adaptive filter can be thought of as a self-adjusting graphic equaliser:
Input
Output
Would be very hard to do with discrete components!
Automatic slider adjustment based on the error

43. Effect of Noise Reduction
Input
Output

44. Speech Compression

45. Voice Recorder Speak into the microphone and record the sound
Play back the sound – can store up to 5 seconds of speech
Implement another version, this time using some form of speech compression algorithm e.g. G.711
Play back the sound – this time can store up to 10 seconds of speech.

46. Wavelets

47. Wavelet Analysis
Analyse audio signal by breaking it down into discrete packets known as “wavelets”.
Narrow Frequency Band
Wide Frequency Band

48. Wavelet Decomposition - Example
Note that a1 and a2 are further decomposed, so they are not required to characterize the signal.

49. Summary

50. Summary of Applications
Applications have been chosen to illustrate a range of DSP techniques
Emphasis on hands-on rather than just theory
Working real-time C code supplied as a starting point for laboratories.

51. Next Steps Find an application you like from those provided.
Load the project onto the TMS320C5505 USB Stick.
Run the project and experiment with it!