FacePlant/src/sensors/BatterySensor.cpp

#include "BatterySensor.h"

void BatterySensor::begin() {
  pinMode(PIN_BATTERY_ADC, INPUT);
  pinMode(PIN_LBO, INPUT);
  pinMode(PIN_CHG, INPUT_PULLUP);  // CHG is LOW when charging

  analogReadResolution(12);  // 12-bit ADC (0-4095)

  Serial.println("[Battery] Initialized");
  Serial.println("[Battery] ADC on GPIO 2, LBO on GPIO 5, CHG on GPIO 4");

  // Initial reading
  _voltage = readBatteryVoltage();
  _percent = voltageToPercent(_voltage);
  _isLow = (_voltage < VOLTAGE_LOW);

  Serial.print("[Battery] Initial voltage: ");
  Serial.print(_voltage);
  Serial.print("V, ");
  Serial.print(_percent);
  Serial.println("%");
}

void BatterySensor::loop() {
  unsigned long now = millis();
  if (now - _lastCheckMs < CHECK_INTERVAL_MS) return;
  _lastCheckMs = now;

  float prevVoltage = _voltage;
  int prevPercent = _percent;
  bool wasLow = _isLow;
  bool wasCharging = _isCharging;

  // Read battery voltage via ADC
  _voltage = readBatteryVoltage();
  _percent = voltageToPercent(_voltage);

  // Check CHG pin (LOW when charging)
  bool chgLow = !digitalRead(PIN_CHG);
  _isCharging = chgLow;

  // Check LBO pin as backup confirmation
  bool lboHigh = digitalRead(PIN_LBO);
  bool lboIndicatesLow = !lboHigh;

  // Battery is low if either voltage is low OR LBO pin indicates low (and not charging)
  _isLow = ((_voltage < VOLTAGE_LOW) || lboIndicatesLow) && !_isCharging;

  // Log significant changes
  if (abs(_percent - prevPercent) >= 5 || _isLow != wasLow || _isCharging != wasCharging) {
    Serial.print("[Battery] Voltage: ");
    Serial.print(_voltage, 2);
    Serial.print("V (");
    Serial.print(_percent);
    Serial.print("%) ");

    if (_isCharging) {
      Serial.print("CHARGING ");
    }

    Serial.print("LBO: ");
    Serial.println(lboHigh ? "OK" : "LOW");

    if (_isLow && !wasLow && !_isCharging) {
      Serial.println("[Battery] ⚠️  LOW BATTERY WARNING - Please recharge!");
    }

    if (_isCharging && !wasCharging) {
      Serial.println("[Battery] 🔌 Charging started");
    } else if (!_isCharging && wasCharging) {
      Serial.println("[Battery] ✓ Charging complete or disconnected");
    }
  }
}

float BatterySensor::readBatteryVoltage() {
  // Take multiple samples and average them for stability
  long sum = 0;
  for (int i = 0; i < SAMPLES; i++) {
    sum += analogRead(PIN_BATTERY_ADC);
    delay(5);
  }
  int avgRaw = sum / SAMPLES;

  // Convert ADC value to voltage at the pin
  // ESP32-C3 ADC: 12-bit (0-4095) maps to 0-3.3V
  float adcVoltage = (avgRaw / 4095.0) * 3.3;

  // Multiply by divider ratio to get actual battery voltage
  float batteryVoltage = adcVoltage * DIVIDER_RATIO;

  return batteryVoltage;
}

int BatterySensor::voltageToPercent(float voltage) {
  // Clamp voltage to valid range
  if (voltage >= VOLTAGE_MAX) return 100;
  if (voltage <= VOLTAGE_MIN) return 0;

  // Linear mapping from voltage to percentage
  // This is a simplified model; LiPo discharge curves are non-linear
  // For better accuracy, you could use a lookup table
  float percent = ((voltage - VOLTAGE_MIN) / (VOLTAGE_MAX - VOLTAGE_MIN)) * 100.0;

  return constrain((int)percent, 0, 100);
}

bool BatterySensor::shouldBlink() const {
  // Blink every 500ms when battery is low (< 20%)
  return (_percent < 20) && ((millis() / 500) % 2 == 0);
}

int BatterySensor::iconFillWidth(int maxWidth) const {
  // Calculate fill width for battery icon
  // Returns 0 to maxWidth based on percentage
  return (_percent * maxWidth) / 100;
}