Replace MIDI clock with internal BPM timer for pixel 6 pulse

Revert:
- Remove midi_clock.h/cpp (was causing cross-core crash)
- Remove real-time MIDI message parsing from midi_transport.cpp

New approach:
- Pixel 6 (and all active LEDs) pulse to internal BPM timer
- Default 120 BPM (500ms beat interval)
- 'bpm <n>' serial command to change tempo (20-300)
- Only calls FastLED.show() when actively pulsing (avoids USB/WS2812 interference)
- 33ms update rate (30fps)
- Inactive LEDs left untouched (no unnecessary show() calls)

include/led_stub.h

@@ -33,6 +33,7 @@ private:
     static const uint8_t NUM_LEDS = 10;
     LedState led_states[NUM_LEDS];
     bool initialized;
+    uint32_t beat_interval_ms = 500;
     
 public:
     DefaultLedStub();
@@ -44,4 +45,5 @@ public:
     void update() override;
 
     void set_mux(PixelStompMux* mux);
+    void set_bpm(uint16_t bpm);
 };

include/midi_clock.h

@@ -1,19 +0,0 @@
-#pragma once
-#include <cstdint>
-
-class MidiClock {
-public:
-    static void tick();
-    static void start();
-    static void stop();
-    static float get_phase();
-    static float get_pulse();
-    static bool is_running();
-
-private:
-    static uint32_t last_tick_time;
-    static uint32_t tick_count;
-    static float tick_interval_ms;
-    static bool running;
-    static const uint8_t TICKS_PER_BEAT = 24;
-};

src/led_stub.cpp

@@ -1,7 +1,7 @@
 #include "led_stub.h"
 #include "pixel_stomp_mux.h"
-#include "midi_clock.h"
 #include <Arduino.h>
+#include <math.h>
 
 static PixelStompMux* mux_ptr = nullptr;
 
@@ -300,40 +300,46 @@ void DefaultLedStub::flash_activity() {
     // LED feedback is handled directly by set_led_state().
 }
 
+void DefaultLedStub::set_bpm(uint16_t bpm) {
+    if (bpm == 0) bpm = 120;
+    beat_interval_ms = 60000 / bpm;
+    Serial.printf("[LED] Pulse BPM set to %d (%dms)\n", bpm, beat_interval_ms);
+}
+
 void DefaultLedStub::update() {
     if (!initialized || !mux_ptr) return;
 
     uint32_t now = millis();
     static uint32_t last_pulse_update = 0;
 
-    if (now - last_pulse_update < 20) return;
+    if (now - last_pulse_update < 33) return;
     last_pulse_update = now;
 
-    bool clock_running = MidiClock::is_running();
+    float phase = (now % beat_interval_ms) / (float)beat_interval_ms;
-    float pulse = 1.0f;
+    float pulse = sinf(M_PI * phase);
-    if (clock_running) {
-        pulse = MidiClock::get_pulse();
-    }
 
+    bool active = false;
     for (int i = 0; i < NUM_LEDS; i++) {
         if (led_states[i].active) {
-            float brightness = clock_running ? (0.5f + 0.5f * pulse) : 1.0f;
+            active = true;
+            float brightness = 0.5f + 0.5f * pulse;
             uint32_t base = pad_base_colors[i];
             uint8_t r = (uint8_t)(((base >> 16) & 0xFF) * brightness);
             uint8_t g = (uint8_t)(((base >> 8) & 0xFF) * brightness);
             uint8_t b = (uint8_t)((base & 0xFF) * brightness);
             mux_ptr->set_led_color(i, r, g, b);
-        } else if (clock_running && i == 6) {
+        } else if (i == 6) {
+            active = true;
             float brightness = 0.3f + 0.7f * pulse;
             uint32_t base = pad_base_colors[6];
             uint8_t r = (uint8_t)(((base >> 16) & 0xFF) * brightness);
             uint8_t g = (uint8_t)(((base >> 8) & 0xFF) * brightness);
             uint8_t b = (uint8_t)((base & 0xFF) * brightness);
             mux_ptr->set_led_color(6, r, g, b);
-        } else {
-            apply_pad_color(i, 0);
         }
     }
 
+    if (active) {
         mux_ptr->show();
+    }
 }

src/main.cpp

@@ -89,6 +89,13 @@ void handle_serial_command(const String& cmd) {
     } else if (cmd == "exp") {
         Serial.printf("[CMD] EXP ADC=%d MIDI=%d\n",
                       exp_pedal.get_raw(), exp_pedal.get_value());
+    } else if (cmd.startsWith("bpm ")) {
+        uint16_t bpm = cmd.substring(4).toInt();
+        if (bpm >= 20 && bpm <= 300) {
+            led_driver.set_bpm(bpm);
+        } else {
+            Serial.println("[CMD] BPM must be 20-300");
+        }
     } else if (cmd == "usb") {
         Serial.printf("[CMD] USB mounted: %s\n", TinyUSBDevice.mounted() ? "YES" : "NO");
         Serial.printf("[CMD] USB ready: %s\n", TinyUSBDevice.ready() ? "YES" : "NO");
@@ -133,6 +140,7 @@ void handle_serial_command(const String& cmd) {
         Serial.println("  red/green/blue - solid colour");
         Serial.println("  pixel0/pixel1 - single pixel test");
         Serial.println("  exp        - expression pedal ADC/MIDI value");
+        Serial.println("  bpm <n>    - set LED pulse tempo (20-300, default 120)");
         Serial.println("  usb        - USB connection status and descriptor info");
         Serial.println("  gpiotest   - raw GPIO pin diagnostic");
         Serial.println("  rawled     - bit-bang WS2812 (no library)");
@@ -356,6 +364,9 @@ void setup() {
     Serial.println("[INIT] Initializing Expression Pedal...");
     exp_pedal.begin();
     
+    Serial.println("[INIT] Setting LED pulse tempo...");
+    led_driver.set_bpm(120);
+
     Serial.println("[INIT] Registering MIDI callbacks...");
     controller.begin();
     

src/midi_clock.cpp

@@ -1,51 +0,0 @@
-#include "midi_clock.h"
-#include <Arduino.h>
-#include <math.h>
-
-uint32_t MidiClock::last_tick_time = 0;
-uint32_t MidiClock::tick_count = 0;
-float MidiClock::tick_interval_ms = 0;
-bool MidiClock::running = false;
-
-void MidiClock::tick() {
-    uint32_t now = millis();
-    if (last_tick_time != 0) {
-        float interval = now - last_tick_time;
-        if (tick_interval_ms == 0) {
-            tick_interval_ms = interval;
-        } else {
-            tick_interval_ms = tick_interval_ms * 0.9f + interval * 0.1f;
-        }
-    }
-    last_tick_time = now;
-    tick_count++;
-    running = true;
-}
-
-void MidiClock::start() {
-    tick_count = 0;
-    last_tick_time = 0;
-    tick_interval_ms = 0;
-    running = true;
-}
-
-void MidiClock::stop() {
-    running = false;
-}
-
-float MidiClock::get_phase() {
-    if (!running || tick_interval_ms == 0) return 0;
-    uint32_t now = millis();
-    float time_since_tick = now - last_tick_time;
-    float sub_phase = time_since_tick / tick_interval_ms;
-    if (sub_phase > 1.0f) sub_phase = 1.0f;
-    return ((tick_count % TICKS_PER_BEAT) + sub_phase) / (float)TICKS_PER_BEAT;
-}
-
-float MidiClock::get_pulse() {
-    return sinf(M_PI * get_phase());
-}
-
-bool MidiClock::is_running() {
-    return running;
-}

src/midi_transport.cpp

@@ -1,5 +1,4 @@
 #include "midi_transport.h"
-#include "midi_clock.h"
 #include <Arduino.h>
 #include "Adafruit_TinyUSB.h"
 
@@ -52,20 +51,6 @@ void UsbMidiTransport::update() {
     while (usb_midi.available()) {
         uint8_t packet[4];
         if (usb_midi.readPacket(packet)) {
-            uint8_t cin = packet[0] & 0x0F;
-
-            if (cin == 0x0F) {
-                uint8_t rt = packet[1];
-                if (rt == 0xF8) {
-                    MidiClock::tick();
-                } else if (rt == 0xFA || rt == 0xFB) {
-                    MidiClock::start();
-                } else if (rt == 0xFC) {
-                    MidiClock::stop();
-                }
-                continue;
-            }
-
             MidiEvent event;
             parse_midi_packet(packet, 4, event);