The beauty of electronics lies in its versatility. With the blend of software, its domain expands to an infinite set. This project aims at building a Keyboard Synthesizer workstation which is a multi- instrument keyboard that can record several different synthesized instruments and playback the track simultaneously. While a commercial, high-end synthesizer may cost you approximately USD 3000, you can design your own keyboard synthesizer in no more than USD seventy five. Besides, you gain a healthy hands-on experience.
The significant hardware interfaces for this project includes a keyboard to play a range of notes from various musical instruments, a user interface which is a phone-style keypad (16-key-8-pin) for command input, LCD for user feedback that displays the various modes/operations the keyboard supports. Using the help menu on the LCD (16×2), user may learn the function of each key on the keypad and switch the current instrument between a piano, drum, guitar, and clarinet; record a track with that instrument; etc. Atmega644 is used as the microcontroller.
The logic flow for the synthesizer is designed as follows:
1. Instrument synthesis through a PWM output running at 62.5 kHz
2. Reading commands from a keypad
3. Reading keyboard input from a keyboard/keypad
4. Storing notes for each track
5. Printing to an LCD
6. Managing the state machine that would control the keyboard
7. Reading input/calculating output on time
The frequency synthesis is done through a table of PWM samples for one cycle of frequency modulated sine wave. The frequency of the note heard is changed by how fast we run through the PWM samples. The PWM output runs at 62.5 KHz.
Most transitions in state are triggered by commands. Every key on the keyboard is associated with a function which when pressed is called. These functions are controlled by a state machine. Writing the state machine for transition control is another milestone in this project and also forms a major portion of the software accomplishments here.
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