This repo contains our code for our the second coursework of the Embedded Systems module (ELEC 96018).

The folder Code/synth contains our code for the synth module. It has these files:

• LUTs.h - Header file containing lookup tables used in the main code. These help with generation of waveforms and effects.
• knob.h - Defines a knob class that is used to encapsulate the properties and functionality of knobs e.g. the update of values in response to received waveforms.
• synth.ino - The main code for the firmware of the synth. Contains implementation of threads and interrupt routines responsible for the different tasks.
• synth.bin - An executable binary compiled from the above code files. Same as our submission for the coursework.

In order to upload the synth implementation to the board, open Arduino, Sketch>Upload.

Alternatively use the compiled binary found in Code/synth/

https://youtu.be/3AHNhz73ujM

We have implemented the functional functional features asked for in the Coursework specification:

• Serial input/output of messages, according to the desired protocol.
• Playing sawtooth waves of correct note frequency without perceptible delay from note press.
• Volume control with exactly 8 increments
• OLED display of volume and notes played.

Additionally, the following advanced features are implemented

• Sine, square, exponential and triangle waveforms.
• Smoothing filter (can be applied on any waveforms)
• Polyphony for sawtooth and triangle waveforms. Note: This is implemented for concurrent key presses, but there is no support for concurrent processing of input serial messages - this is done sequentially (one-by-one) through the queue buffer.
• Vibrato for sawtooth and triangle waveforms.
• Echo for sine waveform.
• Tremolo for all waveforms.
• Superimposition of features configurable from different knobs (see next section on Using the Synth).
• Presence/absence of the effects are indicated on the OLED display with imperceptible lag between turning of knob and change of the display.

All of this is demonstrated in the video linked in the above section.

For visual examples of using the synth, refer to the video linked above.

The knobs are used to adjust different aspects of the sound played. The knob values are adjusted by rotating them clockwise or anticlockwise.

• Knob 0: Choose Filter: 0 - No filtering, 1 - Smoothing filter.
• Knob 1: Change Effect: 0 - No effect, 1 - Vibrato/Echo (if available), 2 - Tremolo.
• Knob 2: Change Waveform: 0 - Saw, 1 - Sine, 2 - Square, 3 - Exponential, 4 - Triangle.
• Knob 3: Change volume: 0 to 16 in increments of 2

The joystick currently does not have any functionality assigned to it. It was found to be too sensitive for any practical usage that we could implement. A possible future extension to our software could be to create a functionality that is controlled by joystick inputs. However for now, moving the joystick will have no effect.

This configuration corresponds to the functional (non-advanced) requirements in the coursework specification. It plays a sawtooth waveform without any advanced features.

The knob configuration must be set so that the following display is seen on the OLED:

The effects created by the different knobs (see section on Knobs) can be combined with each other in any manner without interference. An example can be seen at the end of the linked video.

• Anushka Kulkarni

• Rishil Patel

• Aaman Rebello

• Victor Florea