Exponential smoothing on expression pedal ADC (factor 8) to filter noise

include/expression_pedal.h

@@ -29,6 +29,7 @@ private:
     uint32_t last_read_time;
 
     uint16_t current_raw;
+    uint16_t smoothed_raw;
     uint16_t cal_min;
     uint16_t cal_max;
 

src/expression_pedal.cpp

@@ -10,6 +10,7 @@ ExpressionPedal::ExpressionPedal(uint8_t adc_pin)
     , midi_cc(4)
     , last_read_time(0)
     , current_raw(0)
+    , smoothed_raw(0)
     , cal_min(36)
     , cal_max(1180)
 {
@@ -21,7 +22,8 @@ void ExpressionPedal::begin() {
     pinMode(adc_pin, INPUT);
     delay(10);
     current_raw = analogRead(adc_pin);
-    current_value = adc_to_midi(current_raw);
+    smoothed_raw = current_raw;
+    current_value = adc_to_midi(smoothed_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);
@@ -34,7 +36,8 @@ void ExpressionPedal::update(UsbMidiTransport& midi) {
     last_read_time = now;
 
     current_raw = analogRead(adc_pin);
-    uint8_t new_value = adc_to_midi(current_raw);
+    smoothed_raw = (smoothed_raw * 7 + current_raw + 4) / 8;
+    uint8_t new_value = adc_to_midi(smoothed_raw);
 
     if (new_value > current_value + HYSTERESIS ||
         new_value + HYSTERESIS < current_value ||