/*
   STM32F103C6 - Dual Accurate VU Meter (dBu scale)
   Input DC max ~2.0V from envelope follower
   Output 5 LEDs per channel
   Accurate 300ms time constant + dBu mapping
*/

const int chL = PA2;
const int chR = PA3;

// LED Left
int ledL[5] = {PB0, PB1, PB10, PB11, PB12};
// LED Right
int ledR[5] = {PB13, PB14, PB15, PA8, PA9};

// ADC voltage reference
const float VREF = 3.3;

// Max envelope voltage for +5 dBu
const float VMAX = 2.0;

// dBu mapping range
const float dBuMin = -20.0;
const float dBuMax = +5.0;

// smoothing (VU 300ms)
float smoothL = 0;
float smoothR = 0;
const float alpha = 0.003; // ~300ms at ~1kHz loop

// LED thresholds in dBu
float vuLevel[5] = {
  -14.0,   // LED1
  -7.0,    // LED2
  -2.0,    // LED3
   0.0,    // LED4
  +3.0     // LED5
};

void setup() {
  analogReadResolution(12);

  for(int i=0; i<5; i++){
    pinMode(ledL[i], OUTPUT);
    pinMode(ledR[i], OUTPUT);
  }
}

void loop() {
  // -------------------------
  // 1. Read ADC
  // -------------------------
  float vL = analogRead(chL) * (VREF / 4095.0);
  float vR = analogRead(chR) * (VREF / 4095.0);

  if(vL > VMAX) vL = VMAX;
  if(vR > VMAX) vR = VMAX;

  // -------------------------
  // 2. Smooth 300ms (accurate VU behavior)
  // -------------------------
  smoothL += alpha * (vL - smoothL);
  smoothR += alpha * (vR - smoothR);

  // -------------------------
  // 3. Convert to dBu scale
  // -------------------------
  float dBuL = dBuMin + (smoothL / VMAX) * (dBuMax - dBuMin);
  float dBuR = dBuMin + (smoothR / VMAX) * (dBuMax - dBuMin);

  // -------------------------
  // 4. Update LEDs
  // -------------------------
  showVU(ledL, dBuL);
  showVU(ledR, dBuR);

  delayMicroseconds(900); // ~1 kHz loop for correct smoothing
}

// ------------------------------------
// LED Control based on dBu thresholds
// ------------------------------------
void showVU(int *led, float dBu){
  for(int i=0; i<5; i++){
    if(dBu >= vuLevel[i]) digitalWrite(led[i], HIGH);
    else                   digitalWrite(led[i], LOW);
  }
}