Playing notes over I2S

AudioThread.cpp

@@ -0,0 +1,67 @@
+#include "AudioThread.h"
+#include "SharedState.h"
+#include <I2S.h>
+#include <math.h>
+
+// I2S Pin definitions
+// You may need to change these to match your hardware setup (e.g., for a specific DAC).
+const int I2S_BCLK_PIN = 9;  // Bit Clock (GP9)
+const int I2S_LRC_PIN  = 10; // Left-Right Clock (GP10)
+const int I2S_DOUT_PIN = 11; // Data Out (GP11)
+
+// Audio parameters
+const int SAMPLE_RATE = 44100;
+const int16_t AMPLITUDE = 16383; // Use a lower amplitude to avoid clipping (max is 32767 for 16-bit)
+
+// Create an I2S output object
+I2S i2s(OUTPUT);
+
+// --- Synthesizer State ---
+// Frequencies for a C-Major scale to pick from
+const float NOTE_FREQUENCIES[] = {
+  261.63, 293.66, 329.63, 349.23, 392.00, 440.00, 493.88, 523.25
+};
+const int NUM_NOTES = sizeof(NOTE_FREQUENCIES) / sizeof(NOTE_FREQUENCIES[0]);
+
+float currentFrequency = 440.0f;
+double phase = 0.0;
+unsigned long lastNoteChangeTime = 0;
+// ---
+
+void setupAudio() {
+  // Configure I2S pins
+  i2s.setBCLK(I2S_BCLK_PIN);
+  i2s.setDATA(I2S_DOUT_PIN);
+
+  // Set the sample rate and start I2S communication
+  i2s.setFrequency(SAMPLE_RATE);
+  if (!i2s.begin()) {
+    Serial.println("Failed to initialize I2S!");
+    while (1); // Halt on error
+  }
+
+  // Seed the random number generator from an unconnected analog pin
+  randomSeed(analogRead(A0));
+}
+
+void loopAudio() {
+  unsigned long now = millis();
+
+  // Every 500ms, pick a new random note to play
+  if (now - lastNoteChangeTime > 500) {
+    lastNoteChangeTime = now;
+    int noteIndex = random(0, NUM_NOTES);
+    currentFrequency = NOTE_FREQUENCIES[noteIndex];
+    Serial.println("Playing note: " + String(currentFrequency) + " Hz");
+  }
+
+  // Generate the sine wave sample
+  double phaseIncrement = 2.0 * M_PI * currentFrequency / SAMPLE_RATE;
+  phase = fmod(phase + phaseIncrement, 2.0 * M_PI);
+  int16_t sample = static_cast<int16_t>(AMPLITUDE * sin(phase));
+
+  // Write the same sample to both left and right channels (mono audio).
+  // This call is blocking and will wait until there is space in the DMA buffer.
+  i2s.write(sample);
+  i2s.write(sample);
+}

AudioThread.h

@@ -0,0 +1,7 @@
+#ifndef AUDIOTHREAD_H
+#define AUDIOTHREAD_H
+
+void setupAudio();
+void loopAudio();
+
+#endif // AUDIOTHREAD_H

README.md

@@ -24,23 +24,41 @@ This guide provides the blueprint for building your own.
 | **Power**              | 3.7V LiPo Battery and a 5V booster/charger board (e.g., Adafruit PowerBoost).  |
 | **MIDI Circuit Parts** | 6N138 or 6N137 Optocoupler, 1N4148 Diode, various resistors (see diagram).     |
 
-## Powering Your Synth (Battery Operation)
+## Powering Your Synth
 
-To make the synth truly portable, we'll use a LiPo battery and a booster board. This is critical for providing stable power to all components.
+You can power the synth either from a portable LiPo battery or directly from USB.
+
+### Battery Operation (Portable)
+
+To make the synth truly portable, use a LiPo battery and a 5V booster/charger board. This provides stable power to all components.
 
 > **LIPO BATTERY WARNING**: LiPo batteries are powerful but require careful handling.
 > *   **Never** use a LiPo battery without a dedicated protection and charging circuit like the PowerBoost.
 > *   Do not puncture, bend, or short-circuit a LiPo battery.
 
-### Wiring for Power:
-
 1.  Connect the **LiPo battery** to the JST connector on the **PowerBoost board**.
 2.  Connect the **PowerBoost's 5V output** to the **Pico's VBUS pin (Pin 40)**. This powers the Pico.
 3.  Connect the **PowerBoost's 5V output** to the **VCC/VIN pin of your I2S Audio Module**.
-4.  Connect the **PowerBoost's GND** to one of the **Pico's GND pins**.
+4.  Connect the **PowerBoost's GND** to one of the **Pico's GND pins**. This creates a common ground.
-5.  Connect this **common ground** to the **GND pins of all other components** (OLED, I2S Module, Encoder, Potentiometer, MIDI circuit).
 
-This setup ensures everything shares a common ground and that the power-hungry components get the stable 5V they need, while the Pico's onboard regulator provides 3.3V for the lower-power parts.
+### USB Operation
+
+If you don't need battery power, you can run the synth from a USB source (like a computer or wall adapter). The wiring is simpler.
+
+There are two ways to power the components:
+
+**Option 1 (Simplest): Power everything from 3.3V**
+The PCM5102A DAC chip runs natively on 3.3V. This is the easiest and safest wiring method for USB operation.
+1.  Power the Pico by connecting its **micro-USB port** to a USB power source.
+2.  Connect the Pico's **3V3(OUT) pin (Pin 36)** to the VCC/VIN pins of **all** components: the I2S Module, OLED, Rotary Encoder, Potentiometer, and MIDI circuit.
+3.  Ensure all components share a **common ground** with one of the Pico's GND pins.
+
+**Option 2: Power I2S Module from 5V (with protection)**
+If you prefer to give the audio module a separate 5V supply from USB. For good measure, adding a Schottky diode (e.g., 1N5817) is recommended to protect against any potential reverse voltage.
+1.  Power the Pico via its **micro-USB port**.
+2.  Connect the Pico's **VBUS pin (Pin 40)** to the **anode (+)** of a Schottky diode. Connect the **cathode (-)** of the diode to the **VCC/VIN pin of your I2S Audio Module**.
+3.  Connect the Pico's **3V3(OUT) pin (Pin 36)** to power the OLED, Encoder, Potentiometer, and MIDI circuit.
+4.  Ensure all components share a **common ground**.
 
 ## Wiring & Connections
 
@@ -49,11 +67,12 @@ Establish a **common ground** by connecting the ground from your PowerBoost boar
 | Component          | Pico Pin           | Description                                    |
 | ------------------ | ------------------ | ---------------------------------------------- |
 | **I2S Audio Module** |                    |                                                |
-| VCC                | 5V from PowerBoost | Power for the amplifier                        |
+| VCC                | 3.3V or 5V Source (see Power section) | Power for the amplifier                        |
 | GND                | Common GND         | Ground                                         |
 | DIN (Data)         | GP11 (Pin 15)      | I2S Data Out                                   |
 | BCLK (Bit Clock)   | GP9 (Pin 12)       | I2S Bit Clock                                  |
 | LRCK (Word Clock)  | GP10 (Pin 14)      | I2S Left/Right Clock                           |
+| SCK (System Clock) | GND                | **PCM5102 Only**: Connect to GND for internal PLL |
 | **SSD1306 OLED**   |                    |                                                |
 | VCC                | 3V3 (OUT) (Pin 36) | 3.3V Power                                     |
 | GND                | Common GND         | Ground                                         |

RP2040_NoiceSynth.ino

@@ -1,275 +1,45 @@
-/**
+#include "SharedState.h"
- * NoiceSynth - A Compact RP2040 Synthesizer
+#include "UIThread.h"
- *
+#include "AudioThread.h"
- * This sketch provides the foundational code for a portable MIDI synthesizer
- * based on the Raspberry Pi Pico (RP2040).
- *
- * Features implemented:
- * - I2S audio output for a simple sawtooth oscillator.
- * - MIDI input handling (Note On/Off) via TRS jack to control the oscillator.
- * - OLED display for visual feedback (current note, volume).
- * - Analog volume control via a potentiometer.
- * - Basic rotary encoder reading (framework for future parameter control).
- *
- * Libraries Required (Install via Arduino Library Manager):
- * - Adafruit GFX Library
- * - Adafruit SSD1306
- * - MIDI Library (by Forty Seven Effects)
- *
- * The I2S library by Earle F. Philhower, III is included with the RP2040 board core.
- */
-
-#include <I2S.h>
-#include <Wire.h>
-#include <Adafruit_GFX.h>
-#include <Adafruit_SSD1306.h>
-#include <MIDI.h>
-
-// --- Pin Definitions (as per README.md) ---
-// I2S Audio
-#define I2S_BCLK_PIN 9
-#define I2S_LRCK_PIN 10
-#define I2S_DATA_PIN 11
-
-// I2C OLED Display
-#define OLED_SDA_PIN 4
-#define OLED_SCL_PIN 5
-
-// Controls
-#define ENCODER_CLK_PIN 12
-#define ENCODER_DT_PIN  13
-#define ENCODER_SW_PIN  14
-#define VOL_POT_PIN     26 // ADC0
-
-// MIDI Input
-#define MIDI_RX_PIN 1 // UART0 RX
-
-// --- Constants ---
-#define SCREEN_WIDTH 128
-#define SCREEN_HEIGHT 64
-#define OLED_RESET    -1 // Reset pin # (or -1 if sharing Arduino reset pin)
-
-#define SAMPLE_RATE 44100
-#define BITS_PER_SAMPLE 16
-
-// --- Global Objects ---
-I2S i2s;
-Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
-
-// Create a MIDI object listening on Serial1 (GP0/GP1)
-MIDI_CREATE_INSTANCE(HardwareSerial, Serial1, MIDI);
-
-// --- Synthesizer State Variables ---
-volatile float g_note_frequency = 0.0;
-volatile bool g_note_on = false;
-volatile float g_volume = 0.5;
-
-#ifdef TEST_OUT
-// C Natural Minor Scale notes (C3 to C5) for testing
-const byte c_minor_scale_notes[] = {
-  48, 50, 51, 53, 55, 56, 58, // C3 octave
-  60, 62, 63, 65, 67, 68, 70, // C4 octave
-  72                          // C5
-};
-#endif
-
-// Oscillator phase
-float g_phase = 0.0;
-
-// Rotary encoder state
-int g_encoder_value = 0;
-int g_last_clk_state;
-
-// --- Audio Generation Callback ---
-// This function is called by the I2S library on the second core (by default)
-// to fill the audio buffer. It must be fast and should not do any allocations.
-void fill_audio_buffer(int16_t* buffer, size_t buffer_size) {
-  if (!g_note_on || g_note_frequency <= 0.0) {
-    // If no note is playing, fill the buffer with silence.
-    for (size_t i = 0; i < buffer_size; i++) {
-      buffer[i] = 0;
-    }
-    return;
-  }
-
-  // Calculate how much to increment the phase for each sample to get the desired frequency.
-  float phase_increment = (2.0 * PI * g_note_frequency) / SAMPLE_RATE;
-
-  // The maximum amplitude for a 16-bit signed integer.
-  const int16_t max_amplitude = 32767;
-
-  for (size_t i = 0; i < buffer_size; i += 2) { // Process in stereo pairs
-    // Generate a sawtooth wave sample (-1.0 to 1.0)
-    float sample = (g_phase / PI) - 1.0;
-
-    // Increment and wrap the phase
-    g_phase += phase_increment;
-    if (g_phase >= 2.0 * PI) {
-      g_phase -= 2.0 * PI;
-    }
-
-    // Apply volume and scale to 16-bit integer range
-    int16_t final_sample = static_cast<int16_t>(sample * max_amplitude * g_volume);
-
-    // Write the same sample to both left and right channels
-    buffer[i] = final_sample;     // Left channel
-    buffer[i + 1] = final_sample; // Right channel
-  }
-}
-
-// --- MIDI Callback Functions ---
-void handleNoteOn(byte channel, byte note, byte velocity) {
-  // Convert MIDI note number to frequency
-  g_note_frequency = 440.0 * pow(2.0, (note - 69.0) / 12.0);
-  g_note_on = true;
-  g_phase = 0.0; // Reset phase for a clean attack
-}
-
-void handleNoteOff(byte channel, byte note, byte velocity) {
-  g_note_on = false;
-  g_note_frequency = 0.0;
-}
-
-// --- Helper Functions ---
-void updateDisplay() {
-  display.clearDisplay();
-  display.setCursor(0, 0);
-
-  display.println(F("    NoiceSynth"));
-  display.println(F("--------------------"));
-
-  if (g_note_on) {
-    display.print(F("Note Freq: "));
-    display.print(g_note_frequency, 2);
-    display.println(F(" Hz"));
-  } else {
-    display.println(F("Note: Off"));
-  }
-
-  display.print(F("Volume: "));
-  display.print(static_cast<int>(g_volume * 100));
-  display.println(F("%"));
-
-  display.print(F("Encoder: "));
-  display.println(g_encoder_value);
-
-  display.display();
-}
-
-void readEncoder() {
-  int new_clk_state = digitalRead(ENCODER_CLK_PIN);
-  // Check for a change on the CLK pin (a "tick" of the encoder)
-  if (new_clk_state != g_last_clk_state && new_clk_state == LOW) {
-    // Read the DT pin to determine direction
-    if (digitalRead(ENCODER_DT_PIN) == LOW) {
-      g_encoder_value++; // Clockwise
-    } else {
-      g_encoder_value--; // Counter-clockwise
-    }
-  }
-  g_last_clk_state = new_clk_state;
-}
-
 
 void setup() {
   Serial.begin(115200);
+  delay(2000); // Wait for serial monitor
+  Serial.println(F("Starting NoiceSynth..."));
 
-  // --- Initialize I2C and Display ---
+  setupUI();
-  Wire.setSDA(OLED_SDA_PIN);
+  setupAudio();
-  Wire.setSCL(OLED_SCL_PIN);
-  Wire.begin();
 
-  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3C for 128x64
+  Serial.println(F("Started."));
-    Serial.println(F("SSD1306 allocation failed"));
+
-    for (;;); // Don't proceed, loop forever
+  // Enable Watchdog
+  lastLoop0Time = millis();
+  lastLoop1Time = millis();
+  watchdogActive = true;
 }
-  display.clearDisplay();
-  display.setTextColor(SSD1306_WHITE);
-  display.setTextSize(1);
-  display.println("NoiceSynth Booting...");
-  display.display();
-  delay(1000);
 
-  // --- Initialize Controls ---
+void loop1() {
-  pinMode(ENCODER_CLK_PIN, INPUT_PULLUP);
+  if (!watchdogActive) {
-  pinMode(ENCODER_DT_PIN, INPUT_PULLUP);
+    delay(100);
-  pinMode(ENCODER_SW_PIN, INPUT_PULLUP);
+    return;
-  g_last_clk_state = digitalRead(ENCODER_CLK_PIN);
-
-#ifndef TEST_OUT
-  // --- Initialize MIDI ---
-  // The optocoupler circuit inverts the signal, so we must enable inverse logic.
-  Serial1.setRX(MIDI_RX_PIN);
-  Serial1.setTX(0); // Not using TX
-  Serial1.begin(31250);
-  Serial1.setRXInverse(true);
-
-  MIDI.setHandleNoteOn(handleNoteOn);
-  MIDI.setHandleNoteOff(handleNoteOff);
-  MIDI.begin(MIDI_CHANNEL_OMNI);
-  Serial.println("MIDI Initialized.");
-#else
-  Serial.println("TEST_OUT mode enabled. Playing random C minor notes.");
-  // Seed random from noise on the volume pot ADC pin
-  randomSeed(analogRead(VOL_POT_PIN));
-#endif
-  // --- Initialize I2S Audio ---
-  i2s.setBCLK(I2S_BCLK_PIN);
-  i2s.setLRCK(I2S_LRCK_PIN);
-  i2s.setDATA(I2S_DATA_PIN);
-
-  // Set the audio callback function
-  i2s.setBufferCallback(fill_audio_buffer);
-
-  if (!i2s.begin(I2S_STEREO, SAMPLE_RATE, BITS_PER_SAMPLE)) {
-    Serial.println("Failed to initialize I2S!");
-    while (1); // Stop forever
   }
-  Serial.println("I2S Initialized.");
+  unsigned long now = millis();
+  lastLoop1Time = now;
+  if (watchdogActive && (now - lastLoop0Time > 1000)) {
+    Serial.println(F("Core 0 Freeze detected! Rebooting..."));
+    rp2040.reboot();
+  }
+
+  loopAudio();
 }
 
 void loop() {
-#ifdef TEST_OUT
+  unsigned long now = millis();
-  static uint32_t last_note_event = 0;
+  lastLoop0Time = now;
-  static bool is_playing_test_note = false;
+  if (watchdogActive && (now - lastLoop1Time > 1000)) {
-  const uint16_t note_duration = 250; // ms
+    Serial.println(F("Core 1 Freeze detected! Rebooting..."));
-  const uint16_t note_gap = 50;       // ms
+    rp2040.reboot();
-
-  // Check if it's time to turn off the current note
-  if (is_playing_test_note && (millis() - last_note_event > note_duration)) {
-    handleNoteOff(1, 0, 0); // Turn note off
-    is_playing_test_note = false;
-    last_note_event = millis(); // Reset timer for the gap
   }
 
-  // Check if it's time to play a new note
+  loopUI();
-  if (!is_playing_test_note && (millis() - last_note_event > note_gap)) {
-    // Pick a random note from the scale
-    int note_index = random(sizeof(c_minor_scale_notes) / sizeof(c_minor_scale_notes[0]));
-    byte midi_note = c_minor_scale_notes[note_index];
-
-    // Call NoteOn to set frequency and state
-    handleNoteOn(1, midi_note, 127); // Channel and velocity don't matter here
-    is_playing_test_note = true;
-    last_note_event = millis(); // Reset timer for the duration
-  }
-#else
-  // Listen for incoming MIDI messages
-  MIDI.read();
-#endif
-
-  // Read the volume potentiometer (Pico ADC is 12-bit, 0-4095)
-  // We use a bit of filtering by averaging with the old value to reduce noise.
-  float new_volume = analogRead(VOL_POT_PIN) / 4095.0f;
-  g_volume = (g_volume * 0.95) + (new_volume * 0.05);
-
-  // Read the rotary encoder
-  readEncoder();
-
-  // Update the display periodically
-  static uint32_t last_display_update = 0;
-  if (millis() - last_display_update > 100) { // Update 10 times/sec
-    last_display_update = millis();
-    updateDisplay();
-  }
 }

SharedState.cpp

@@ -0,0 +1,5 @@
+#include "SharedState.h"
+
+volatile unsigned long lastLoop0Time = 0;
+volatile unsigned long lastLoop1Time = 0;
+volatile bool watchdogActive = false;

SharedState.h

@@ -0,0 +1,10 @@
+#ifndef SHAREDSTATE_H
+#define SHAREDSTATE_H
+
+#include <Arduino.h>
+
+extern volatile unsigned long lastLoop0Time;
+extern volatile unsigned long lastLoop1Time;
+extern volatile bool watchdogActive;
+
+#endif // SHAREDSTATE_H

UIThread.cpp

@@ -0,0 +1,12 @@
+#include "UIThread.h"
+#include "SharedState.h"
+#include <Arduino.h>
+
+void setupUI() {
+  // This is the UI thread, running on core 0. For this example, we do nothing here.
+}
+
+void loopUI() {
+  // The loop on core 0 is responsible for updating the UI. In this simple example, it does nothing.
+  delay(100);
+}

UIThread.h

@@ -0,0 +1,7 @@
+#ifndef UITHREAD_H
+#define UITHREAD_H
+
+void setupUI();
+void loopUI();
+
+#endif // UITHREAD_H