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332 lines
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<title>MIDI Breadboard Instrument (Desk Rave & 16-Track Symphony) — Projects — Ertunç Özbay</title>
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<meta name="description" content="Project documentation, Python RLE MIDI-to-C compiler code, ESP-IDF C99 firmware, and downloads for the 16-Track MIDI Breadboard Instrument by Ertunç Özbay.">
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<span class="brand-mark" aria-hidden="true">EÖ</span>
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Ertunç Özbay
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<span class="brand-subtitle">embedded // hardware // open-source</span>
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<article>
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<header class="workshop-hero">
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<div class="card-meta">
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<span class="badge badge-experimental">Status: Active Breadboard Prototype</span>
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<span>Project 02 // ESP32 Dual-Core • ESP-IDF C99 • FreeRTOS • Python RLE</span>
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</div>
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<h1><span class="gradient-title">MIDI Breadboard Instrument — Desk Rave & 16-Track Symphony</span></h1>
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<p class="hero-lead">
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A standalone, dual-core ESP32 MIDI synthesizer, drum sequencer, and 30 FPS SPI OLED visualizer written in ESP-IDF v5.2.2 (C99 / FreeRTOS), powered by a custom Run-Length Encoding (RLE) Python MIDI-to-C compiler.
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</p>
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<p class="reading-width">
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What started as making a passive piezo buzzer squeak evolved into a full 16-track embedded music box with live kick/hi-hat drum transients, hardware PCNT quadrature rotary controls for real-time tempo and volume scaling, and dual-core FreeRTOS task isolation.
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</p>
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<div class="button-row">
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<a class="btn btn-primary" href="http://34.57.151.250:3000/ertunc-ozbay/midi-breadboard-instrument" rel="noopener noreferrer">💻 View GitHub Repo</a>
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<a class="btn btn-emerald" href="../assets/downloads/desk_rave_16track_esp32.c" download="mmcontroller.c">⬇ Download 16-Track C Firmware (.c)</a>
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<a class="btn btn-cyan" href="../assets/downloads/midi_to_c.py" download="midi_to_c.py">🐍 Download midi_to_c.py</a>
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<a class="btn btn-secondary" href="/assets/downloads/midi-breadboard-instrument.zip">📦 Repo (.zip)</a>
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<a class="btn btn-youtube" href="#poc-video">🎬 Watch PoC Video Slot</a>
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</div>
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</header>
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<!-- YouTube Proof-of-Concept Video Placeholder -->
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<section id="poc-video" class="poc-video-section" aria-labelledby="midi-video-heading">
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<div class="poc-video-card">
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<span class="section-label">🎬 Proof of Concept // YouTube Video Showcase</span>
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<h2 id="midi-video-heading">YouTube Proof-of-Concept Demonstration</h2>
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<div class="poc-video-screen" role="region" aria-label="YouTube Proof of Concept Video Placeholder">
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<div class="poc-play-badge" aria-hidden="true">
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<div class="poc-play-triangle"></div>
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</div>
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<span class="poc-status-pill">🎥 YouTube PoC Video — Recording / Coming Soon</span>
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<div class="poc-video-title">Desk Rave 16-Track ESP32 MIDI Synthesizer — Live Audio & 30 FPS OLED Demo</div>
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<p class="poc-video-desc">
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Upcoming YouTube video showcasing live playback across the 16-track flash playlist (Careless Whisper, Rondo Alla Turca, Seven Nation Army +2 octave transpose), real-time rotary speed/volume tweaking, and synchronized kick/hi-hat buzzers + LEDs.
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</p>
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</div>
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</div>
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</section>
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<figure class="schematic-frame" aria-label="MIDI Breadboard Instrument Component Diagram">
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<img class="zoomable-img" src="../assets/images/midi-breadboard-layout.svg" alt="Block diagram of the MIDI Breadboard Instrument showing the MIDI conversion script producing C code for the breadboard system" width="760" height="320">
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<figcaption class="schematic-caption">
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Software-to-hardware pipeline: Python RLE MIDI compiler (<code>midi_to_c.py</code>) generating flash-resident <code>SequenceStep</code> struct arrays for the dual-core ESP32 breadboard synthesizer.
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</figcaption>
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</figure>
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<section class="section-block" aria-labelledby="p3-gallery">
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<span class="section-label">01 // Hardware Build Gallery</span>
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<h2 id="p3-gallery">Breadboard Prototype Photos (Click to Zoom)</h2>
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<div class="card-grid">
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<figure class="card card-synth" style="margin:0;">
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<img class="zoomable-img" src="../assets/images/MIDI_FIRST.jpg" alt="Full dual-breadboard overview of the ESP32 MIDI Breadboard Instrument" style="width:100%; height:auto; border-radius:8px; margin-bottom:0.75rem;">
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<figcaption>
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<strong>Full Breadboard Layout:</strong> Dual-breadboard build featuring the ESP32 DevKit, 1.3" 7-pin SPI OLED display, KY-040 rotary encoder, tactile buttons, passive melody piezo, and dual active drum buzzers.
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</figcaption>
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</figure>
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<figure class="card card-synth" style="margin:0;">
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<img class="zoomable-img" src="../assets/images/MIDI_SECOND.jpg" alt="Active 1.3-inch SPI OLED visualizer running at 30 FPS on the breadboard" style="width:100%; height:auto; border-radius:8px; margin-bottom:0.75rem;">
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<figcaption>
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<strong>30 FPS Live OLED Visualizer:</strong> Custom 5×7 font renderer displaying track code (<code>WHISP</code>), rotary mode (<code>SPD</code> / <code>VOL</code>), kick/hi-hat drum boxes, and dynamic frequency bars.
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</figcaption>
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</figure>
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<figure class="card card-synth" style="margin:0;">
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<img class="zoomable-img" src="../assets/images/MIDI_THIRD.jpg" alt="Close-up of the rotary encoder, tactile buttons, LEDs, and three buzzers" style="width:100%; height:auto; border-radius:8px; margin-bottom:0.75rem;">
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<figcaption>
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<strong>Controls & Acoustic Stage:</strong> Close-up of the rotary encoder, Play/Pause and Next Track buttons, green/red drum LEDs, and the 3-buzzer audio stage.
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</figcaption>
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</figure>
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</div>
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</section>
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<!-- Terminal Commands & Source Code Section -->
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<section class="section-block" aria-labelledby="p3-code">
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<span class="section-label">02 // Terminal Commands, Python RLE Compiler & C99 Firmware</span>
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<h2 id="p3-code">Build, Flash & MIDI Conversion Commands</h2>
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<p class="reading-width">
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Clone the repository, convert any `.mid` file into an RLE-compressed C struct array using `scripts/midi_to_c.py`, and flash the 16-track firmware to an ESP32:
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</p>
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<div class="code-window">
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<div class="code-window-header">
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<span class="code-window-title">
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<span class="code-dots"><span class="code-dot red"></span><span class="code-dot amber"></span><span class="code-dot green"></span></span>
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bash — Convert MIDI to C & Flash ESP32 Firmware (ESP-IDF v5.2.2)
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</span>
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<button type="button" class="copy-code-btn" data-copy-code>📋 Copy Commands</button>
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</div>
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<pre><code># 1. Clone the repository
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git clone http://34.57.151.250:3000/ertunc-ozbay/midi-breadboard-instrument.git
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cd midi-breadboard-instrument
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# 2. (Optional) Convert a custom .mid file into an RLE-compressed C struct array
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pip install mido
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python3 scripts/midi_to_c.py scripts/midillis/Alla_Turca/Alla_Turca.mid > my_track.h
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# 3. Build and flash the 16-track firmware to ESP32
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source ~/esp/esp-idf/export.sh
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idf.py build
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idf.py -p /dev/ttyUSB0 flash monitor</code></pre>
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</div>
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<h3>Python RLE MIDI-to-C Compiler (<code>scripts/midi_to_c.py</code>)</h3>
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<p class="reading-width">
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To prevent fragmented MIDI delta-times from strobing the LEDs/OLED at 30+ Hz and exhausting flash memory, <code>midi_to_c.py</code> merges contiguous identical states via Run-Length Encoding and routes Channel 10 + bass notes (`< MIDI 50`) to hardware percussion buzzers:
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</p>
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<div class="code-window">
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<div class="code-window-header">
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<span class="code-window-title">
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<span class="code-dots"><span class="code-dot red"></span><span class="code-dot amber"></span><span class="code-dot green"></span></span>
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python3 — scripts/midi_to_c.py (RLE Compression & Drum Routing Engine)
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</span>
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<button type="button" class="copy-code-btn" data-copy-code>📋 Copy Code</button>
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</div>
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<pre><code>#!/usr/bin/env python3
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import sys, mido
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def convert_midi_to_c(midi_filename):
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mid = mido.MidiFile(midi_filename)
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safe_name = midi_filename.split('/')[-1].replace('.mid', '').replace('-', '_')
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print(f"const SequenceStep midi_{safe_name}[] = {{")
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active_melody_notes = set()
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time_accum = 0.0
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trigger_kick = trigger_hat = False
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rle_freq, rle_dur, rle_kick, rle_hat = -1, 0, False, False
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for msg in mid:
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time_accum += msg.time
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if msg.type in ['note_on', 'note_off'] and time_accum > 0.01:
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duration_ms = int(time_accum * 1000)
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freq = int(440.0 * (2.0 ** ((max(active_melody_notes) - 69) / 12.0))) if active_melody_notes else 0
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# RLE Engine: coalesce contiguous identical frequency & drum states
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if freq == rle_freq and trigger_kick == rle_kick and trigger_hat == rle_hat:
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rle_dur += duration_ms
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else:
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if rle_dur > 0:
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print(f" {{{rle_freq}, {rle_dur}, {str(rle_kick).lower()}, {str(rle_hat).lower()}}},")
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rle_freq, rle_dur, rle_kick, rle_hat = freq, duration_ms, trigger_kick, trigger_hat
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time_accum, trigger_kick, trigger_hat = 0.0, False, False</code></pre>
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</div>
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<h3>Dual-Core FreeRTOS Music & Visualizer Architecture (<code>main/mmcontroller.c</code>)</h3>
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<div class="code-window">
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<div class="code-window-header">
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<span class="code-window-title">
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<span class="code-dots"><span class="code-dot red"></span><span class="code-dot amber"></span><span class="code-dot green"></span></span>
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c99 — main/mmcontroller.c (SequenceStep Struct & Dual-Core Task Pinning)
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</span>
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<button type="button" class="copy-code-btn" data-copy-code>📋 Copy Code</button>
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</div>
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<pre><code>typedef struct {
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uint16_t frequency; // Melody pitch in Hz (driven by 13-bit LEDC PWM on GPIO 25)
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uint16_t duration; // Step duration in ms (scaled live by PCNT rotary speed)
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bool kick_drum; // Triggers Active Buzzer 1 (GPIO 26) + Kick LED (GPIO 21)
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bool hi_hat; // Triggers Active Buzzer 2 (GPIO 27) + Hat LED (GPIO 22)
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} SequenceStep;
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void app_main(void) {
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printf("Desk Rave: 16-Track Symphony Edition Initializing...\n");
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init_hardware();
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// Core 0: 30 FPS SPI OLED Framebuffer Visualizer & 50ms Button Polling
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xTaskCreatePinnedToCore(oled_visualizer_task, "oled_task", 4096, NULL, 4, NULL, 0);
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xTaskCreatePinnedToCore(button_task, "btn_task", 4096, NULL, 5, NULL, 0);
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// Core 1: Dedicated Real-Time Audio Synthesizer & PCNT Rotary Scaling
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xTaskCreatePinnedToCore(buzzer_sequence_task, "music_task", 4096, NULL, 5, NULL, 1);
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}</code></pre>
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</div>
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</section>
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<section class="section-block reading-width" aria-labelledby="p3-components">
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<span class="section-label">03 // Confirmed Hardware & Pinout</span>
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<h2 id="p3-components">ESP32 Pinout & Architecture Specifications</h2>
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<table class="spec-table">
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<thead>
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<tr>
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<th scope="col">Component / Peripheral</th>
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<th scope="col">ESP32 Pin / Interface</th>
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<th scope="col">Function</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td><strong>Microcontroller</strong></td>
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<td>ESP32 (Dual-Core Xtensa @ 160 MHz)</td>
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<td>ESP-IDF v5.2.2 + FreeRTOS dual-core execution</td>
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</tr>
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<tr>
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<td><strong>Rotary Encoder CLK / DT</strong></td>
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<td><code>GPIO 32</code> / <code>GPIO 33</code></td>
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<td>Hardware PCNT quadrature tracking (1000 ns glitch filter)</td>
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</tr>
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<tr>
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<td><strong>Rotary Encoder SW</strong></td>
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<td><code>GPIO 16</code> (Active Low)</td>
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<td>Toggles knob & OLED HUD between Speed (<code>0.2x–3.0x</code>) and Volume (<code>0%–100%</code>)</td>
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</tr>
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<tr>
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<td><strong>Pause / Next Buttons</strong></td>
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<td><code>GPIO 13</code> / <code>GPIO 14</code> (Active Low)</td>
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<td>Play/Pause toggle and 16-track playlist cycling</td>
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</tr>
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<tr>
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<td><strong>Passive Buzzer (Melody)</strong></td>
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<td><code>GPIO 25</code> (LEDC 13-bit PWM)</td>
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<td>Main melody synthesizer driven by hardware LEDC Timer 0</td>
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</tr>
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<tr>
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<td><strong>Active Buzzer 1 & 2 (Drums)</strong></td>
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<td><code>GPIO 26</code> (Kick) / <code>GPIO 27</code> (Hi-Hat)</td>
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<td>Physical percussion transients on drum steps</td>
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</tr>
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<tr>
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<td><strong>Kick & Hi-Hat LEDs</strong></td>
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<td><code>GPIO 21</code> (Kick) / <code>GPIO 22</code> (Hi-Hat)</td>
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<td>Visual beat indicators synchronized to drum hits</td>
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</tr>
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<tr>
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<td><strong>1.3" 7-Pin SPI OLED</strong></td>
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<td><code>CS: 5, DC: 2, RES: 4, MOSI: 23, SCK: 18</code></td>
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<td>10 MHz SPI2 display running custom 30 FPS visualizer on Core 0</td>
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</tr>
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</tbody>
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</table>
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</section>
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<section class="section-block reading-width" aria-labelledby="p3-playlist">
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<span class="section-label">04 // Flash Memory Playlist</span>
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<h2 id="p3-playlist">The 16-Track Symphony</h2>
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<ol>
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<li><strong>Careless Whisper</strong> (Extended Club Edit)</li>
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<li><strong>Take On Me</strong> (EDM Build-up Edition)</li>
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<li><strong>Never Gonna Give You Up / Rickroll</strong> (Double Chorus)</li>
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<li><strong>Can't Help Falling In Love</strong> (Wedding Mix)</li>
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<li><strong>Gimme! Gimme! Gimme!</strong> (Midnight Rave)</li>
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<li><strong>Für Elise</strong> (Beethoven Trance)</li>
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<li><strong>Symphony No. 40</strong> (Mozart Intense Strings)</li>
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<li><strong>Super Mario Bros.</strong> (Main Theme)</li>
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<li><strong>Pirates of the Caribbean 1</strong> (He's a Pirate)</li>
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<li><strong>Pirates of the Caribbean 2</strong> (The Black Pearl)</li>
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<li><strong>Rondo Alla Turca</strong> (Mozart)</li>
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<li><strong>Tetris</strong> (Korobeiniki)</li>
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<li><strong>Sonic the Hedgehog</strong> (Green Hill Zone)</li>
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<li><strong>Castlevania</strong> (Vampire Killer)</li>
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<li><strong>Seven Nation Army</strong> (Transposed +2 Octaves for piezo resonance)</li>
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<li><strong>Mega Man 2</strong> (Dr. Wily Stage)</li>
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</ol>
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||
</section>
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<strong>Ertunç Özbay</strong> — Electrical & Electronics Engineering Student • <a href="mailto:ertunc.ozbay@outlook.com">ertunc.ozbay@outlook.com</a>
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