Digisax

STARLITE

Description

STARLITE is a minimalist Digital Saxophone (Digisax) controlled by ESP32-S3.

Inspiration

This project is intended to be a cost effective, customisable alternative to commercially available wind synths. STARLITE can be used for both performance and silent practice. It weds my two favorite hobbies: music and tinkering.

Features:

• realistic ergonomics
• UI in the form of an OLED display and rotary encoder, to control master volume and timbre
• differential pressure sensor for responsive breath control
• pressure tube and bleed tube to simulate realistic resistance to blowing
• audio synthesised locally
• 3x7 key matrix featuring MX Black switches
• power via 5V barrel jack
• DAC with headphone output

The neck can be blown into directly, but an alto saxophone mouthpiece is recommended. (Not included in this project.)

OnShape link: https://cad.onshape.com/documents/a64dba8dfd86a5efa1851173/w/8b62b2d00aa632cf961d9b4c/e/8ecfcb79b78c17c244b3f0aa

Schematic and PCB

A pdf version can be found under pcb/unconnected_pcb.

PCB front

PCB back

NOTE: Kicad project contatining an unconnected, partially routed pcb can be found under pcb/unconnected_pcb. A fully routed, panelised pcb can be found under pcb/panelised_pcb. Gerber files were generated from the latter.

Assembly

1. All parts can be handsoldered. I recommend soldering the key-switches last.
2. 3D printed parts to contain M3 heatset inserts.
3. Cut two lengths of food grade silicone tubing, 70mm (pressure tube) and 240mm (bleed tube) in length.
4. All plumbing is a push fit. Connect the pressure tube between the neck and pressure sensor. Bleed tube carries condensation from the neck to the bottom of the instrument. Holes in the right-hand-pinky-keys can hold the bleed tube in place.
5. All keycaps are a push fit. See images at bottom of page for correct placement.
6. Wrap cork around the neck to ensure an airtight fit with the mouthpiece.

3D printed parts:

BOM

Code

Firmware is written in C++.

Column pins use the ESP-32's internal pullup, and all row pins are set to high. I implemented a loop where all the rows are pulled high by default, and any column which is detected as low is matched with the key's corresponding row.

At the moment the code detects simultaneous key presses and prints the note which the current fingering corresponds to. Matrix and fingering mappings can be found in the code/ directory.

Note synthesis and volume control via the rotary encoder will be implemented once the project is built.

#include <Arduino.h>
#include <map>
#include <initializer_list>

// =====================
// MATRIX PINS
// =====================

int Rows[] = {7, 15, 16, 17, 18, 8, 9};
int Columns[] = {10, 11, 12};

// =====================
// KEY NAMES
// =====================

const char* saxKey[7][3] =
{
    {"Octave1","L1","Ls1"},
    {"fork1","Bf1","Ls2"},
    {"Rs1","L2","Ls3"},
    {"Rs2","L3","Gsh1"},
    {"Rs3","R1","Csh1"},
    {"Dsh1","R2","LB1"},
    {"C1","R3","LBf1"}

More images

Acknowledgements <3

Massive thank you to Rehan for sacrificing his sleep to write the firmware.

Also to Sua for designing a BANGING zine.