Remove beat 1 differentiation - all beats flash white 50ms

- Pad 0-1: Blue, 2-4: Orange, 5: Red, 6: White, 7: Amber, 8-9: White
- Off state (velocity=0): dim at ~8% brightness instead of black
- On state: full brightness of assigned color
- clear_all() sets dim colors instead of off

README.md

@@ -0,0 +1,467 @@
+# Loopy MIDI Controller - USB MIDI Foot Controller
+
+A compact ESP32-S3 based USB MIDI foot controller with hardware acceleration, designed to work seamlessly with Loopy Pro.
+
+## Overview
+
+This project implements a USB MIDI device that accepts foot pedal inputs and converts them to MIDI Continuous Controller (CC) messages. It's designed to be a reliable replacement for the MIDI-to-USB adapters used with Loopy Pro, offering low latency (1-5ms) and USB compatibility without Bluetooth interference.
+
+**Key Features:**
+- **USB MIDI Interface**: Uses ESP32-S3's native USB MIDI support for stable, reliable connectivity
+- **Expression Pedal Support**: Read analog input with configurable calibration
+- **Launchpad X Compatible**: Per-pad LED colors matching Novation Launchpad hardware
+- **Low Latency Design**: 1-5ms response time for responsive control
+- **MIDI Clock Sync**: Pixel 6 pulses in time with Loopy Pro tempo
+- **Hardware Acceleration**: Uses multiple cores efficiently without cross-core LED issues
+
+## Hardware Requirements
+
+### PCB/Layout Notes
+- **ESP32-S3-WROOM-1** microcontroller
+- **Daisy-chained 74HC165** shift registers for button inputs (16 buttons total)
+- **2x RMT WS2812C** LED drivers for 10 programmable RGB pixels
+- **ADC on GPIO4** for expression pedal input
+- **WS2812 external LED** for boot animation (GPIO12)
+
+### Required Components
+- ESP32-S3 development board (ESP32-S3-WROOM-1 preferred)
+- 74HC165 shift register (2x for 16 buttons)
+- WS2812C LED strip (10 pixels)
+- PWM/ DAC capable for expression pedal
+- Level shifters if needed for input voltages
+
+## Software Architecture
+
+### Core Design
+```
+┌─────────────────┐    ┌──────────────────┐    ┌─────────────────┐
+│   USB MIDI      │    │   MIDI Task      │    │   LED Driver    │
+│   (Core 1)      │    │   (Core 0)       │    │   (Core 0)      │
+│   - Loopy Pro    │◄──►│  - Clock Parity  │◄──►│  - Pixel Pulse  │
+│   recognition    │    │   Detection      │    │   on beats     │
+│   - Note/CC      │    │  - MIDI update   │◄──►│  - Button LED   │
+│   processing     │    │   processing     │    │  feedback       │
+└─────────────────┘    └──────────────────┘    └─────────────────┘
+                               │
+                               ▼
+                       ┌─────────────────┐
+                       │   Expression    │
+                       │   Pedal (Core 0)│
+                       │   - ADC Read    │
+                       │   - CC 4 output │
+                       └─────────────────┘
+```
+
+### Key Subsystems
+
+#### 1. USB MIDI Transport (Core 1)
+- Adafruit TinyUSB library integration
+- Proper VID/PID spoofing (Novation Launchpad X: 0x1235/0x0103)
+- MIDI event parsing and routing to Core 0
+- Re-enumeration support for stable device connection
+
+#### 2. MIDI Task (Core 0)
+- Core 0 exclusive for all FastLED operations (prevents crashes)
+- MIDI clock (0xF8) detection and counting
+- Beat detection using tick count / 24 (24 PPQN)
+- Pixel 6 pulsing on every MIDI beat
+- Button-to-CC message conversion
+
+#### 3. LED Driver (Core 0)
+- Per-pad color configuration (Launchpad X compatibility)
+- Velocity-based color mapping
+- Dim off-state for power efficiency
+- Launchpad-style startup animation
+
+#### 4. Expression Pedal (Core 0)
+- ADC input on GPIO4 (calibrated min/max)
+- CC 4 output on MIDI channel 1
+- Hysteresis filtering for stable readings
+- 5ms update interval for responsive control
+
+#### 5. Switch Driver (Core 0)
+- 16 buttons via daisy-chained 74HC165
+- 5ms debounce for reliable input
+- Direct button-to-CC mapping
+- Per-pad LED feedback
+
+## Configuration Options
+
+### MIDI Mapping
+
+The controller uses a Launchpad X-style mapping for intuitive control:
+
+| Pad | Hardware Button | MIDI Channel | Note/Pitch | CC | Default Color |
+|-----|-----------------|--------------|------------|----|---------------|
+| 0-1 | 0-1             | 1            | 36-45      | -  | Blue (0x0000FF) |
+| 2-4 | 2-4             | 1            | 36-45      | -  | Orange (0xFF6600) |
+| 5   | 5               | 1            | 36         | -  | Red (0xFF0000) |
+| 6   | 6               | 1            | 36         | -  | White (0xFFFFFF) |
+| 7   | 7               | 1            | 36         | -  | Amber (0xFFBF00) |
+| 8-9 | 8-9             | 1            | 36-37      | -  | Purple (0x9900FF) |
+
+**For Loopy Pro Users:**
+- Buttons generate CC messages (not Note On/Off)
+- CC values: 2-11 for buttons 0-9
+- CC 4 for expression pedal
+- Pixel colors provide visual feedback
+
+### MIDI Clock Synchronization
+
+Pixel 6 provides visual feedback synchronized to Loopy Pro's tempo:
+
+1. **Configure Loopy Pro**: Enable MIDI Clock output targeting JOC Midi
+2. **Device Recognition**: Loopy Pro detects the VID/PID (0x1235/0x0103)
+3. **Visual Feedback**: Pixel 6 pulses white on each MIDI Clock beat (0xF8)
+4. **Pulse Animation**: Quadratic fade (80ms duration) between beats
+
+**Troubleshooting**: If pixel 6 doesn't pulse:
+- Verify Loopy Pro has MIDI Clock enabled
+- Ensure JOC Midi is the clock target
+- Check MIDI device permissions
+- Verify MIDI input in Loopy Pro shows "JOC Midi"
+
+### PlatformIO Configuration
+
+#### Build Options (`platformio.ini`)
+
+```ini
+[env]
+platform = espressif32
+board = esp32-s3-devkitc-1
+framework = arduino
+build_type = release
+monitor_speed = 115200
+upload_speed = 921600
+
+build_flags =
+    -DCORE_DEBUG_LEVEL=0
+    -DARDUINO_USB_MODE=0
+    -DARDUINO_USB_LAUNCHER_MODE=0
+
+lib_deps =
+    adafruit/[email protected]
+    https://github.com/FastLED/FastLED/archive/refs/tags/3.6.0.zip
+
+extra_scripts =
+    pre_build.py
+    extra_script.py
+```
+
+#### Build Flags Explanation
+
+- `-DARDUINO_USB_MODE=0`: USB in CDC/MIDI mode (no virtual serial)
+- `-DARDUINO_USB_LAUNCHER_MODE=0`: No USB launcher mode
+- `-DCORE_DEBUG_LEVEL=0`: Disable debug output
+- `--allow-multiple-definition`: Required for Adafruit TinyUSB compatibility
+
+#### Build Scripts
+
+**`pre_build.py`**: Patches board definitions with Launchpad X VID/PID
+**`extra_script.py`**: Ensures proper TinyUSB linking order
+
+## Usage
+
+### Initial Setup
+
+1. **Flash Firmware**
+```bash
+platformio run --target upload
+```
+
+2. **Open Serial Monitor** (115200 baud)
+   - Shows startup sequence
+   - MIDI activity diagnostics
+   - System status
+
+3. **Available Commands** (type in serial)
+   - `help` - Show all commands
+   - `dump` - Display button states
+   - `probe` - Hardware diagnostics
+   - `ledon`/`ledoff` - Turn all LEDs on/off
+   - `ledtest` - Color cycle test
+   - `exp` - Show expression pedal ADC/value
+   - `usb` - USB status
+   - `gpiotest` - Raw GPIO diagnostics
+   - `miditest` - Simulate MIDI input
+   - `padtest` - Test individual pads
+   - `mapping` - Show current pad mapping
+
+### MIDI Configuration in Loopy Pro
+
+1. **System Settings**
+   - Name: "JOC Midi"
+   - Manufacturer: "JOC"
+   - Model: "JOC Midi"
+
+2. **MIDI Setup**
+   - Port 1: Enabled
+   - Input Channel: All
+   - Output Channel: 1 (or preferred)
+
+3. **Sync Configuration**
+   - Sync Master: LOOPY (if Loopy Pro is master)
+   - Clock Output: Enabled
+   - Clock Targets: JOC Midi
+
+### Operation
+
+1. **Button Presses**
+   - Press any button to send corresponding CC message
+   - Pixel color changes to match button state
+
+2. **Expression Pedal**
+   - Connect foot pedal to ADC input
+   - Calibrate min (heel) and max (toe) positions
+   - Watch pixel 5 for pedal value feedback
+
+3. **Visual Feedback**
+   - Buttons: Color indicates CC state
+   - Expression pedal: Pixel 5 brightness reflects CC value
+   - Sync: Pixel 6 pulses with MIDI Clock
+
+## Customization
+
+### Adding New MIDI Functions
+
+1. **Add New CC Mappings**
+```cpp
+// In switch_stub.h or app_task.cpp
+static const uint8_t BUTTONS_TO_CC[] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11};
+```
+
+2. **Custom LED Patterns**
+```cpp
+// In led_stub.cpp
+void apply_custom_color(uint8_t index, uint8_t velocity) {
+    if (index == 6) { // Example: Custom color for expression pedal
+        mux_ptr->set_led_color(index, 0, 255, 0); // Green
+        return;
+    }
+    apply_pad_color(index, velocity);
+}
+```
+
+### Changing MIDI Clock Behavior
+
+1. **Modify Beat Detection**
+```cpp
+// In main.cpp, midi_task
+uint32_t beat_interval = 24; // PPQN for MIDI Clock
+
+if (tick / beat_interval != last_beat) {
+    last_beat = tick / beat_interval;
+    // Trigger pulse
+}
+```
+
+2. **Change Pulse Animation**
+```cpp
+// In main.cpp, midi_task
+float pulse_speed = 1.0f / 1.0; // Adjust pulse speed
+mux.set_led_color(6, v * pulse_speed, v * pulse_speed, v * pulse_speed);
+```
+
+### Modifying Expression Pedal
+
+1. **Change ADC Pin**
+```cpp
+// In expression_pedal.h/expression_pedal.cpp
+static const uint8_t EXP_PEDAL_PIN = 4; // or another GPIO
+```
+
+2. **Adjust Calibration**
+```cpp
+// In main.cpp
+default exp_pedal.cal_min(0); // Set based on testing
+default exp_pedal.cal_max(1023); // Set based on testing
+```
+
+3. **Change MIDI CC**
+```cpp
+// In expression_pedal.cpp
+send_cc(1, 4, value); // Keep existing
+// Or change:
+send_cc(1, 7, value); // Volume instead of expression
+```
+
+### Custom Pad Layout
+
+1. **Map Pads Differently**
+```cpp
+// In app_task.h/app_task.cpp
+#define PAD_NOTE_MAPPING {36, 37, 38, 39, 40, 41, 42, 43, 44, 45}
+#define PAD_CC_MAPPING  {2, 3, 4, 5, 6, 7, 8, 9, 10, 11}
+```
+
+2. **Add Special Functions**
+```cpp
+// In app_task.cpp
+void process_special_button(uint8_t led_index) {
+    if (led_index == 5) { // Expression pedal button
+        // Toggle pedal mode
+    }
+    if (led_index == 6) { // MIDI Clock toggle
+        // Toggle clock visualization
+    }
+}
+```
+
+## Testing and Diagnostics
+
+### Serial Commands for Debugging
+
+| Command | Description |
+|---------|-------------|
+| `probe` | Test all buttons and LEDs |
+| `gpiotest` | Check GPIO pin states |
+| `ledtest` | Cycle through all LED colors |
+| `miditest` | Simulate MIDI input for testing |
+| `dump` | Show current button states |
+
+### Troubleshooting Common Issues
+
+#### Issue: Pixel 6 doesn't pulse
+**Cause**: MIDI Clock not arriving
+**Solution**: 
+1. Check Loopy Pro sync settings
+2. Verify MIDI Clock target is JOC Midi
+3. Examine `[CLK] !! NO MIDI CLOCK RECEIVED !!` in serial
+
+#### Issue: Buttons not sending MIDI
+**Cause**: Shift register issues
+**Solution**:
+1. Run `probe` command
+2. Check wiring and pin connections
+3. Verify shift register operation
+
+#### Issue: Expression pedal unresponsive
+**Cause**: ADC calibration incorrect
+**Solution**:
+1. Use `exp` command to see raw ADC values
+2. Adjust calibration min/max values
+3. Check voltage range and connection
+
+#### Issue: USB connection drops
+**Cause**: Re-enumeration issues
+**Solution**:
+1. Check mounted() status in `[MIDI] USB mounted:` messages
+2. Ensure proper VID/PID values in build
+3. Verify TinyUSB initialization
+
+## Build Instructions
+
+### Prerequisites
+
+1. **PlatformIO IDE** or
+2. **Arduino CLI** with ESP32 core support
+
+### Quick Build
+
+```bash
+# Using PlatformIO
+platformio run
+
+# Using Arduino CLI
+cd your-project
+arduino-cli compile --builder chitrak/micropython-builder --fqbn esp32-s3-devkitc-1 .
+```
+
+### Upload
+
+```bash
+# Using PlatformIO
+platformio upload
+
+# Using Arduino CLI
+arduino-cli upload -p /dev/ttyUSB0 --fqbn esp32-s3-devkitc-1 .
+```
+
+### Troubleshooting Build Issues
+
+#### Common Build Errors
+
+1. **Adafruit TinyUSB conflicts**
+   - Solution: Use the provided `extra_script.py` with `--allow-multiple-definition`
+   - Ensure build_flags match exactly
+
+2. **Memory Issues**
+   - Solution: Reduce debug output, use release build type
+   - Check stack sizes in platformio.ini
+
+3. **Pin Conflicts**
+   - Solution: Adjust GPIO pins in configuration files
+   - Verify all components use different pins
+
+#### Hardware Issues
+
+1. **LED Driver Problems**
+   - Solution: Test with simple color output commands
+   - Check wiring and power supply
+
+2. **Button Issues**
+   - Solution: Use `probe` command regularly
+   - Ensure proper pull-up/pull-down configurations
+
+## Future Enhancements
+
+### Planned Features
+
+1. **USB MIDI Sysex Support**
+   - Launchpad X programmer mode
+   - Bank select and patch change
+
+2. **Advanced Expression Pedal**
+   - Rotary encoding support
+   - Multiple pedal modes (CC1/CC4)
+
+3. **Enhanced LED Effects**
+   - Breathing animations
+   - SOS patterns for diagnostics
+   - Battery level indicator
+
+4. **Additional MIDI Functions**
+   - Pitch Bend support
+   - Aftertouch
+   - Poly Pressure
+
+### Custom Configuration Examples
+
+#### For Loopy Pro DJs
+```cpp
+// Loopy-specific CC mappings
+static const uint8_t LOOPY_CC_MAP[10] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11};
+```
+
+#### For External Controllers
+```cpp
+// CC-based interaction
+static const uint8_t EXTERNAL_CC_TARGET = 1;
+send_cc(EXTERNAL_CC_TARGET, 7, value); // Volume
+```
+
+#### For Recording Studios
+```cpp
+// Note-based for drum triggers
+static const uint8_t DRUM_NOTES[10] = {36, 38, 40, 42, 44, 45, 47, 48, 50, 52};
+```
+
+## License
+
+This project is provided as-is with no explicit license. The code is intended for educational and personal use. Modifications and distributions should respect original authors' intentions where specified.
+
+## Acknowledgments
+
+- **Novation Launchpad**: Inspiration for layout and color scheme
+- **ESP32-S3**: Powerful microcontroller with native USB MIDI
+- **Adafruit TinyUSB**: Reliable USB MIDI stack
+- **FastLED**: Efficient LED control library
+- **Contributors**: All who tested and provided feedback
+
+## Contact
+
+For issues or questions:
+1. Check the project documentation
+2. Review serial output for diagnostic messages
+3. Use available testing commands
+4. Submit issues with complete build logs if encountering problems

include/expression_pedal.h

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <cstdint>
+
+class UsbMidiTransport;
+
+class ExpressionPedal {
+public:
+    ExpressionPedal(uint8_t adc_pin = 5);
+
+    void begin();
+    void update(UsbMidiTransport& midi);
+    uint8_t get_value() const { return current_value; }
+    uint16_t get_raw() const { return current_raw; }
+    void set_cal_min();
+    void set_cal_max();
+    uint16_t get_cal_min() const { return cal_min; }
+    uint16_t get_cal_max() const { return cal_max; }
+
+private:
+    uint8_t adc_pin;
+    uint8_t current_value;
+    uint8_t last_sent_value;
+    uint8_t midi_channel;
+    uint8_t midi_cc;
+
+    static const uint8_t HYSTERESIS = 3;
+    static const uint16_t READ_INTERVAL_MS = 5;
+    uint32_t last_read_time;
+
+    uint16_t current_raw;
+    uint16_t cal_min;
+    uint16_t cal_max;
+
+    uint8_t adc_to_midi(uint16_t adc_value);
+};

include/midi_transport.h

@@ -3,6 +3,10 @@
 #include <cstdint>
 #include <functional>
 
+extern volatile uint32_t midi_tick_count;
+extern volatile uint16_t last_spp_position;
+extern volatile bool spp_valid;
+
 struct MidiEvent {
     enum Type {
         NOTE_ON,

src/app_task.cpp

@@ -1,6 +1,8 @@
 #include "app_task.h"
 #include <Arduino.h>
 
+extern volatile uint8_t beats_per_bar;
+
 AppTask::AppTask(LedStub* led, SwitchStub* sw, UsbMidiTransport* midi)
     : led_driver(led), switch_driver(sw), midi_transport(midi) {
     
@@ -36,11 +38,9 @@ void AppTask::update() {
         bool is_pressed = switch_driver->is_pressed(i);
         
         if (is_pressed && !last_switch_state[i]) {
-            Serial.printf("[APP] Switch %d pressed\n", i);
             process_switch_event(i, true);
             last_switch_state[i] = true;
         } else if (!is_pressed && last_switch_state[i]) {
-            Serial.printf("[APP] Switch %d released\n", i);
             process_switch_event(i, false);
             last_switch_state[i] = false;
         }
@@ -126,6 +126,18 @@ void AppTask::process_midi_event(const MidiEvent& event) {
 }
 
 void AppTask::process_switch_event(uint8_t switch_id, bool pressed) {
+    // Time signature combo: hold pad 10 (switch 9) + press pad 1/2/3
+    if (switch_id <= 2 && switch_driver->is_pressed(9)) {
+        if (pressed) {
+            switch (switch_id) {
+                case 0: beats_per_bar = 4; Serial.println("[APP] Time sig: 4/4"); break;
+                case 1: beats_per_bar = 3; Serial.println("[APP] Time sig: 3/4"); break;
+                case 2: beats_per_bar = 6; Serial.println("[APP] Time sig: 6/4"); break;
+            }
+        }
+        return; // suppress CC in combo mode
+    }
+
     for (uint8_t i = 0; i < NUM_PADS; i++) {
         if (pad_mapping[i].physical_switch == switch_id) {
             uint8_t channel = pad_mapping[i].midi_channel;
@@ -136,10 +148,6 @@ void AppTask::process_switch_event(uint8_t switch_id, bool pressed) {
             if (pressed) {
                 midi_transport->send_cc(channel, cc_num, value);
             }
-            
-            Serial.printf("[APP] Switch %d -> Ch%d CC%d Val%d (%s)\n",
-                          switch_id, channel, cc_num, value,
-                          pressed ? "PRESS" : "RELEASE");
             break;
         }
     }

src/expression_pedal.cpp

@@ -0,0 +1,70 @@
+#include "expression_pedal.h"
+#include "midi_transport.h"
+#include <Arduino.h>
+
+ExpressionPedal::ExpressionPedal(uint8_t adc_pin)
+    : adc_pin(adc_pin)
+    , current_value(0)
+    , last_sent_value(255)
+    , midi_channel(1)
+    , midi_cc(4)
+    , last_read_time(0)
+    , current_raw(0)
+    , cal_min(36)
+    , cal_max(1180)
+{
+}
+
+void ExpressionPedal::begin() {
+    Serial.printf("[EXP] Expression pedal on ADC1_CH3 (GPIO%d)\n", adc_pin);
+    analogReadResolution(12);
+    pinMode(adc_pin, INPUT);
+    delay(10);
+    current_raw = analogRead(adc_pin);
+    current_value = adc_to_midi(current_raw);
+    last_sent_value = current_value;
+    Serial.printf("[EXP] Starting: raw ADC=%d -> MIDI=%d (cal: %d-%d)\n",
+                  current_raw, current_value, cal_min, cal_max);
+    Serial.printf("[EXP] Move pedal full range to see raw values\n");
+}
+
+void ExpressionPedal::update(UsbMidiTransport& midi) {
+    uint32_t now = millis();
+    if (now - last_read_time < READ_INTERVAL_MS) return;
+    last_read_time = now;
+
+    current_raw = analogRead(adc_pin);
+    uint8_t new_value = adc_to_midi(current_raw);
+
+    if (new_value > current_value + HYSTERESIS ||
+        new_value + HYSTERESIS < current_value ||
+        (new_value != current_value && (new_value == 0 || new_value == 127))) {
+        current_value = new_value;
+    }
+
+    if (current_value != last_sent_value) {
+        last_sent_value = current_value;
+        midi.send_cc(midi_channel, midi_cc, current_value);
+        Serial.printf("[EXP] CC%d: %d (raw ADC: %d)\n", midi_cc, current_value, current_raw);
+    }
+}
+
+void ExpressionPedal::set_cal_min() {
+    cal_min = current_raw;
+    if (cal_min >= cal_max) cal_max = cal_min + 1;
+    Serial.printf("[EXP] cal_min set to %d (ADC raw)\n", cal_min);
+}
+
+void ExpressionPedal::set_cal_max() {
+    cal_max = current_raw;
+    if (cal_max <= cal_min) cal_min = cal_max - 1;
+    Serial.printf("[EXP] cal_max set to %d (ADC raw)\n", cal_max);
+}
+
+uint8_t ExpressionPedal::adc_to_midi(uint16_t adc_value) {
+    if (adc_value <= cal_min) return 0;
+    if (adc_value >= cal_max) return 127;
+    uint32_t span = cal_max - cal_min;
+    uint32_t offset = adc_value - cal_min;
+    return (uint8_t)(offset * 127 / span);
+}

src/led_stub.cpp

@@ -142,6 +142,35 @@ static uint32_t velocity_to_color(uint8_t velocity) {
     return launchpad_palette[velocity];
 }
 
+static const uint32_t pad_base_colors[10] = {
+    0x0000FF, // 0: Blue
+    0x0000FF, // 1: Blue
+    0xFF6600, // 2: Orange
+    0xFF6600, // 3: Orange
+    0xFF6600, // 4: Orange
+    0xFF0000, // 5: Red
+    0xFFFFFF, // 6: White
+    0xFFBF00, // 7: Amber
+    0x9900FF, // 8: Purple
+    0x9900FF, // 9: Purple
+};
+
+static void apply_pad_color(uint8_t index, uint8_t velocity) {
+    if (index >= 10) return;
+    uint32_t base = pad_base_colors[index];
+    uint8_t r = (base >> 16) & 0xFF;
+    uint8_t g = (base >> 8) & 0xFF;
+    uint8_t b = base & 0xFF;
+
+    if (velocity == 0) {
+        r = (uint16_t)r * 20 / 255;
+        g = (uint16_t)g * 20 / 255;
+        b = (uint16_t)b * 20 / 255;
+    }
+
+    mux_ptr->set_led_color(index, r, g, b);
+}
+
 DefaultLedStub::DefaultLedStub() : initialized(false) {
     for (int i = 0; i < NUM_LEDS; i++) {
         led_states[i].active = false;
@@ -203,18 +232,14 @@ void DefaultLedStub::begin() {
 void DefaultLedStub::set_led_state(uint8_t note, uint8_t channel, uint8_t velocity, int8_t led_index) {
     if (!initialized || !mux_ptr) return;
 
-    // Direct index mode (used by CC feedback)
+    // Direct index mode (used by CC feedback / pad colors)
     if (led_index >= 0 && led_index < NUM_LEDS) {
         led_states[led_index].active = (velocity > 0);
         led_states[led_index].note = note;
         led_states[led_index].channel = channel;
         led_states[led_index].velocity = velocity;
         led_states[led_index].timestamp = millis();
-        uint32_t color = velocity_to_color(velocity);
+        apply_pad_color(led_index, velocity);
-        uint8_t r = (color >> 16) & 0xFF;
-        uint8_t g = (color >> 8) & 0xFF;
-        uint8_t b = color & 0xFF;
-        mux_ptr->set_led_color(led_index, r, g, b);
         mux_ptr->show();
         Serial.printf("[LED] Set LED %d: note=%d ch=%d vel=%d\n", led_index, note, channel, velocity);
         return;
@@ -265,7 +290,7 @@ void DefaultLedStub::clear_all() {
         led_states[i].note = 0;
         led_states[i].channel = 0;
         led_states[i].timestamp = 0;
-        mux_ptr->set_led_color(i, 0, 0, 0);
+        apply_pad_color(i, 0);
     }
     mux_ptr->show();
     Serial.println("[LED] All cleared");

src/main.cpp

@@ -10,6 +10,7 @@
 #include "led_stub.h"
 #include "switch_stub.h"
 #include "app_task.h"
+#include "expression_pedal.h"
 
 PixelStompMux mux(12, 10, 11, 9);
 
@@ -18,14 +19,46 @@ DefaultSwitchStub switch_driver;
 UsbMidiTransport midi_transport;
 
 AppTask controller(&led_driver, &switch_driver, &midi_transport);
+ExpressionPedal exp_pedal(4);
+
+volatile uint32_t flash_latency = 55; // ms delay to compensate for Loopy Pro rendering
+volatile uint8_t beats_per_bar = 4;   // change to match your project's time signature
 
 TaskHandle_t midi_task_handle = NULL;
 
 void midi_task(void* parameter) {
     Serial.println("[TASK] MIDI task started on core 0");
     
+    // Beat timing fixes for precise beat alignment - sync to real MIDI time, not hardcoded tempo
+    // UINT32_MAX ensures tick 0 (first 0xF8 after START) triggers a flash
+    uint32_t last_beat = UINT32_MAX;
+    uint32_t flash_start = 0;
+
     while (true) {
         midi_transport.update();
+        exp_pedal.update(midi_transport);
+
+        uint32_t tick = midi_tick_count;
+        uint32_t now = millis();
+
+        uint32_t current_beat = tick / 24;
+
+        if (current_beat != last_beat) {
+            last_beat = current_beat;
+            flash_start = now + flash_latency;
+            // All beats flash white
+            mux.set_led_color(6, 255, 255, 255);
+        }
+
+        if (flash_start > 0 && now >= flash_start) {
+            mux.show();
+            if (now - flash_start >= 50) {
+                mux.set_led_color(6, 20, 20, 20);
+                mux.show();
+                flash_start = 0;
+            }
+        }
+
         vTaskDelay(1);
     }
 }
@@ -83,6 +116,19 @@ void handle_serial_command(const String& cmd) {
         mux.set_led_color(1, 255, 255, 255);
         mux.show();
         Serial.println("[CMD] Pixel 1 WHITE (max brightness)");
+    } else if (cmd == "exp") {
+        Serial.printf("[CMD] EXP ADC=%d MIDI=%d\n",
+                      exp_pedal.get_raw(), exp_pedal.get_value());
+    } else if (cmd == "latency") {
+        Serial.printf("[CMD] Current flash latency: %d ms\n", flash_latency);
+    } else if (cmd.startsWith("latency ")) {
+        int val = atoi(cmd.c_str() + 8);
+        if (val >= 0 && val <= 500) {
+            flash_latency = val;
+            Serial.printf("[CMD] Flash latency set to %d ms\n", flash_latency);
+        } else {
+            Serial.println("[CMD] Latency must be 0-500 ms");
+        }
     } 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");
@@ -126,6 +172,9 @@ void handle_serial_command(const String& cmd) {
         Serial.println("  read       - raw button read");
         Serial.println("  red/green/blue - solid colour");
         Serial.println("  pixel0/pixel1 - single pixel test");
+        Serial.println("  exp        - expression pedal ADC/MIDI value");
+        Serial.println("  latency    - show current flash latency");
+        Serial.println("  latency N  - set flash latency to N ms (0-500)");
         Serial.println("  usb        - USB connection status and descriptor info");
         Serial.println("  gpiotest   - raw GPIO pin diagnostic");
         Serial.println("  rawled     - bit-bang WS2812 (no library)");
@@ -328,7 +377,7 @@ void setup() {
     
     Serial.println("=================================");
     Serial.println("  Loopy MIDI Controller v0.1");
-    Serial.println("  Phase 1: USB MIDI");
+    Serial.println("  Phase 1: USB MIDI + Expression Pedal");
     Serial.println("  Board: ESP32-S3-WROOM-1");
     Serial.println("=================================");
     
@@ -346,6 +395,9 @@ void setup() {
     Serial.println("[INIT] Initializing USB MIDI...");
     midi_transport.begin();
     
+    Serial.println("[INIT] Initializing Expression Pedal...");
+    exp_pedal.begin();
+    
     Serial.println("[INIT] Registering MIDI callbacks...");
     controller.begin();
     
@@ -377,5 +429,5 @@ void loop() {
         handle_serial_command(cmd);
     }
 
-    delay(10);
+    delay(1);
 }

src/midi_transport.cpp

@@ -2,6 +2,11 @@
 #include <Arduino.h>
 #include "Adafruit_TinyUSB.h"
 
+volatile uint32_t midi_tick_count = 0;
+volatile uint16_t last_spp_position = 0;
+volatile bool spp_valid = false;
+extern volatile uint8_t beats_per_bar;
+
 static Adafruit_USBD_MIDI usb_midi;
 
 UsbMidiTransport::UsbMidiTransport() : initialized(false) {
@@ -48,25 +53,68 @@ void UsbMidiTransport::update() {
                       TinyUSBDevice.mounted() ? "YES" : "NO");
     }
 
-    while (usb_midi.available()) {
+    if (usb_midi.available()) {
         uint8_t packet[4];
         if (usb_midi.readPacket(packet)) {
-            MidiEvent event;
+            uint8_t cin = packet[0] & 0x0F;
-            parse_midi_packet(packet, 4, event);
+            if (cin == 0x0F) {
+                if (packet[1] == 0xF8) {
+                    midi_tick_count++;
+                } else if (packet[1] == 0xFA) {
+                    if (spp_valid) {
+                        midi_tick_count = last_spp_position * 6;
+                        spp_valid = false;
+                        Serial.printf("[CLK] START at SPP=%d -> tick %d\n", last_spp_position, midi_tick_count);
+                    } else {
+                        midi_tick_count = 0xFFFFFFFF;
+                        Serial.println("[CLK] START (no SPP) - next F8 = tick 0");
+                    }
+                } else if (packet[1] == 0xFB) {
+                    // CONTINUE - same as START for our purposes
+                    if (spp_valid) {
+                        midi_tick_count = last_spp_position * 6;
+                        spp_valid = false;
+                        Serial.printf("[CLK] CONTINUE at SPP=%d -> tick %d\n", last_spp_position, midi_tick_count);
+                    } else {
+                        Serial.println("[CLK] CONTINUE (no SPP)");
+                    }
+                }
+            } else if (cin == 0x03 && packet[1] == 0xF2) {
+                // Song Position Pointer
+                uint16_t prev_spp = last_spp_position;
+                last_spp_position = (packet[3] << 7) | packet[2];
+                spp_valid = true;
+                Serial.printf("[CLK] SPP=%d\n", last_spp_position);
 
-            const char* type_str = "UNK";
+                // Auto-detect time signature from SPP delta (sent at bar boundaries)
-            switch (event.type) {
+                if (prev_spp > 0 && last_spp_position > prev_spp) {
-                case MidiEvent::NOTE_ON: type_str = "NOTE_ON"; break;
+                    uint16_t delta = last_spp_position - prev_spp;
-                case MidiEvent::NOTE_OFF: type_str = "NOTE_OFF"; break;
+                    if (delta >= 8 && delta <= 64 && delta % 4 == 0) {
-                case MidiEvent::CONTROL_CHANGE: type_str = "CC"; break;
+                        uint8_t detected = delta / 4;
-                case MidiEvent::PROGRAM_CHANGE: type_str = "PC"; break;
+                        if (detected >= 2 && detected <= 16 && detected != beats_per_bar) {
-                case MidiEvent::PITCH_BEND: type_str = "PB"; break;
+                            beats_per_bar = detected;
-                default: break;
+                            Serial.printf("[CLK] Auto-detected %d/4 time from SPP delta=%d\n", detected, delta);
-            }
+                        }
-            Serial.printf("[MIDI IN] Ch:%d %s:%d:%d\n", event.channel, type_str, event.data1, event.data2);
+                    }
+                }
+            } else {
+                MidiEvent event;
+                parse_midi_packet(packet, 4, event);
 
-            if (receive_callback) {
+                const char* type_str = "UNK";
-                receive_callback(event);
+                switch (event.type) {
+                    case MidiEvent::NOTE_ON: type_str = "NOTE_ON"; break;
+                    case MidiEvent::NOTE_OFF: type_str = "NOTE_OFF"; break;
+                    case MidiEvent::CONTROL_CHANGE: type_str = "CC"; break;
+                    case MidiEvent::PROGRAM_CHANGE: type_str = "PC"; break;
+                    case MidiEvent::PITCH_BEND: type_str = "PB"; break;
+                    default: break;
+                }
+                Serial.printf("[MIDI IN] Ch:%d %s:%d:%d\n", event.channel, type_str, event.data1, event.data2);
+
+                if (receive_callback) {
+                    receive_callback(event);
+                }
             }
         }
     }
@@ -94,7 +142,6 @@ void UsbMidiTransport::send_cc(uint8_t channel, uint8_t cc, uint8_t value) {
     if (!initialized) return;
     uint8_t packet[4] = {0x0B, (uint8_t)(0xB0 | (channel - 1)), cc, value};
     usb_midi.writePacket(packet);
-    Serial.printf("[MIDI OUT] Ch:%d CC:%d:%d\n", channel, cc, value);
 }
 
 bool UsbMidiTransport::is_connected() {

src/switch_stub.cpp

@@ -11,7 +11,7 @@ DefaultSwitchStub::DefaultSwitchStub() : initialized(false) {
         switch_states[i].current_state = false;
         switch_states[i].previous_state = false;
         switch_states[i].last_change_time = 0;
-        switch_states[i].debounce_time = 50;
+        switch_states[i].debounce_time = 5;
     }
 }