1. ECE 477 DESIGN REVIEW PART 2 Team 14

2. Outline Schematic PCB layout Theory of Operation
Software design/development status
Questions / discussion

3. Schematic/Theory of Operation
OVERALL

4. Schematic/Theory of Operation
LCD
Audio Input Signal is a

5. Schematic/Theory of Operation
POWER

6. Schematic/Theory of Operation
AUDIO INPUT

7. Schematic/Theory of Operation
SRAM

8. Silkscreen Top

9. Top Routing

10. Bottom Routing

11. PCB Flooded Top

12. PCB Flooded Bottom

13. Frequency Spectrum of window
Theory of Operation
Split the signal into windows with 1024 samples each. Use a hamming window function on the time domain signal for each 1024 samples. FFT each window separately.
Frequency Spectrum of window
Audio Signal

14. Theory of Operation Extract Peaks from the Spectrum.
Discard Peaks with amplitude less that the minimum value.
Peaks from Window

15. Theory of Operation
Match each frequency with the closest matching note frequency. (this makes up for tuning/off key notes)
For Example: if a 218 is detected, the two closest possibilities are 220 and 207. Therefore the note is matched to 220.

16. Theory of Operation
Check which of the frequencies are multiples of others in order to determine which frequencies are fundamentals.
Example:
Freqs in window:
Amps of freqs:
We figure out that is a multiple of Also is a
multiple of and
The algorithm extracts , , and as the fund freqs.

17. Theory of Operation
Remove harmonics from old notes in successive windows.
Detect Strums using amplitude.
Example:
Prev Window:
Next Window:
Amplitude of jumped meaning that the note has been strummed again.

18. Theory of Operation Convert Frequencies to Tabs and MIDI.
In the case of Tabs, the algorithm tries to pick a fret between 0-5 for the note if possible. If the string is used for a different string, use a different string.
In the case of MIDI, the frequencies are used to generate the file.

19. Sample Output Wav file produced: Matches the Tab played.
Matches the Tab played.

20. Issues
The fundamental frequency doesn’t always have the most dominant amplitude.
One reason for that is: 2 different notes are generating that harmonic (easy to handle).
Example:
is produced from 2 different strings therefore its amplitude can be
expected to be higher.
This also happens for unknown reasons with only 1 string generating the harmonic (problematic).
Therefore the decision of whether both notes are played or
the amplitude is just higher can’t be made easily (this
makes chords that include notes of different octaves hard
to match exactly as a Tab, depending on how we handle this determines if the
chord will lake some notes or not.)

21. Issues
Missing fundamental or phantom fundamental when overtones suggest a fundamental frequency but the sound lacks a component at the fundamental frequency itself.
It is now widely accepted that the brain processes the information present in the overtones to calculate the fundamental frequency. The precise way in which it does so is still a matter of debate, but the processing seems to be based on an autocorrelation involving the timing of neural impulses in the auditory nerve. (wiki)

22. Issues
A chords notes can be spread on multiple windows (since the window size is small). That would make it look like each note is played separately on the Tab.

23. Flowchart/Pseudo-code for Main Program
RAM, FLASH, ADC, LCD, SD Card

24. Hierarchical Block Diagram of Code Organization

25. QUESTIONS / DISCUSSION