Tweak cal_max: 1239 -> 1220

Raw ADC observed range: heel=36, toe=1239.
Maps full pedal travel to MIDI 0-127.

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);
+};

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(1220)
+{
+}
+
+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/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);
 
@@ -18,6 +19,7 @@ DefaultSwitchStub switch_driver;
 UsbMidiTransport midi_transport;
 
 AppTask controller(&led_driver, &switch_driver, &midi_transport);
+ExpressionPedal exp_pedal(4);
 
 TaskHandle_t midi_task_handle = NULL;
 
@@ -26,6 +28,7 @@ void midi_task(void* parameter) {
     
     while (true) {
         midi_transport.update();
+        exp_pedal.update(midi_transport);
         vTaskDelay(1);
     }
 }
@@ -83,6 +86,9 @@ 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 == "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 +132,7 @@ 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("  usb        - USB connection status and descriptor info");
         Serial.println("  gpiotest   - raw GPIO pin diagnostic");
         Serial.println("  rawled     - bit-bang WS2812 (no library)");
@@ -328,7 +335,7 @@ 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 +353,9 @@ 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();