Summary of Digital Music Synthesizer Using Atmel 90s8515 chip
This ECE 476 project is a digital music synthesizer mimicking piano and clarinet sounds using Direct Digital Synthesis. It covers one octave (C4 to C5) with 20 kHz sampling to prevent aliasing, storing 6-bit sine wave data in flash memory. The device supports playing chords and simple melodies like "Jingle Bells."
Parts used in the Digital Music Synthesizer:
- 1 Atmel 90s8515 chip
- 1 STK 500 board
- 2 four-key push buttons
- 2 three-key push buttons
- 1 DAC0808
- 1 LF353 Op-Amp
- 14 10k pull-up resistors
- 2 5.1k resistors
- 1 0.1 uF capacitor
- 1 Amplified speaker
- 1 Power supply
Introduction:
Our ECE 476 Spring 2002 final project is a musical synthesizer that mimics the sounds produced by a piano and a clarinet. We wanted to create a device that could produce different musical signals by direct digital synthesis. Using Fourier analysis of the signals, we were able to imitate the sounds from different musical instruments. In addition, we wanted to give our keyboard users the ability to play multiple note chords to create more interesting music patterns. Working on this project gave us a lot of insight into the nature of sound and how high-end keyboard synthesizers actually operate.
The best part about our project was that once we had finished debugging and assembled our final project, we were able to play simple melodies using our Digital Music Synthesizer. Some of these songs included simple tunes like ‘Jingle Bells’ as well as more complex tunes like ‘Chop Sticks’ which requires more than one note to be played at one time (chords).
High-Level Design:
Sine Wave Generation
The range of the synthesizer covers from middle C (lowest note, C4) to an octave above middle C (highest note, C5) and includes all 11 notes in between including all the sharps and flats. This encompasses an entire octave on a musical scale. The sampling frequency of our synthesizer is 20 kHz which is many times the Nyquist frequency of our highest note (C5 523 Hz) so we avoid the possibility of aliasing. We stored the sine table values for each note into flash memory. Each value in the sine table is 6 bits in resolution. C4, at 262 Hz, has a period of 3.81 ms, so at a sampling rate of 20 kHz, we need 77 samples to represent a single C4 wave. A4, at 440 Hz, has a period of 2.27 ms, so we need 46 samples to create a single A4 wave. Since the period of each note is different and we are using a 20 kHz sample rate, each note has a sine table of a different size. Below is a picture of the piano keys (one full octave) that we implemented and a listing of their corresponding frequencies.
The range of the synthesizer covers from middle C (lowest note, C4) to an octave above middle C (highest note, C5) and includes all 11 notes in between including all the sharps and flats. This encompasses an entire octave on a musical scale. The sampling frequency of our synthesizer is 20 kHz which is many times the Nyquist frequency of our highest note (C5 523 Hz) so we avoid the possibility of aliasing. We stored the sine table values for each note into flash memory. Each value in the sine table is 6 bits in resolution. C4, at 262 Hz, has a period of 3.81 ms, so at a sampling rate of 20 kHz, we need 77 samples to represent a single C4 wave. A4, at 440 Hz, has a period of 2.27 ms, so we need 46 samples to create a single A4 wave. Since the period of each note is different and we are using a 20 kHz sample rate, each note has a sine table of a different size.
Parts List:
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Parts List
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For more detail: Digital Music Synthesizer
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What musical range does the synthesizer cover?
The synthesizer covers from middle C (C4) to an octave above middle C (C5), including all sharps and flats. -
How does the project avoid aliasing?
It uses a 20 kHz sampling frequency, which is many times higher than the Nyquist frequency of the highest note. -
Where are the sine table values stored?
The sine table values for each note are stored into flash memory. -
What resolution do the sine table values have?
Each value in the sine table has a 6-bit resolution. -
Can users play chords with this device?
Yes, the keyboard allows users to play multiple note chords to create interesting music patterns. -
Which songs were successfully played on the final device?
Simple tunes like Jingle Bells and complex tunes requiring chords like Chop Sticks were played.
