#include <Battery.h>

Battery battery(3400, 4200, A0,12); //(Battery voltage varies between 3.4V (empty) and 4.2V (full charge) in Li-ion/LiPo batteries.
//To convert raw ADC readings into actual battery percentage, the system needs a reference range (3400–4200 mV).
//The analog pin (A0) reads a voltage between 0V and 3.3V (scaled using a voltage divider).
//ADC resolution determines measurement accuracy (12-bit means values range from 0–4095).12 indicates the ADC Resolution bits for Glyph )
/**
 * 1 cell li-ion/li-poly battery wired to A0 before voltage booster, on demand sensing on pin 3, linear mapping function
 * https://github.com/rlogiacco/BatterySense#lesser-than-5v-with-voltage-booster
 **/

void setup() 
{
	Serial.begin(115200);
	while (!Serial);
	battery.begin(3300,1.585); //(voltage divider A voltage divider is a simple electrical circuit that reduces a higher voltage to a lower voltage. It is commonly used in battery voltage measurement to ensure that the ESP32 (or any microcontroller) receives a safe voltage within its ADC (Analog-to-Digital Converter range).
//1.585 → Voltage Divider Ratio
//Since batteries typically output voltages higher than ESP32’s ADC limit (3.3V max), a voltage divider is used to scale it down.
//If your board has a different resistor divider, this value must be changed.
//How to Change for Different Batteries?
//If you have a higher voltage battery (e.g., 7.4V or 12V), you need:
//Larger R1 to drop more voltage.
//A new voltage divider ratio in the battery.begin() function.)
}

void loop() 
{
   //Blinks the Onboard LED to indicate that the battery is connected and being measured.
	digitalWrite(1, HIGH);
	delay(500);
	digitalWrite(1, LOW);
	delay(500);

	Serial.print("Battery voltage is ");
	Serial.print(battery.voltage());
	Serial.print(" (");
	Serial.print(battery.level());
	Serial.println("%)");
}

const float CALIBRATION_FACTOR = 1.14;

// ADC configuration
#define BATTERY_PIN A0
const float VOLTAGE_DIVIDER_RATIO = 2.0;       // 200k:200k divider
const float ADC_REF_VOLTAGE = 3.3;             // ESP32 ADC reference
const float CALIBRATION_FACTOR = 1.14;
const float MIN_VOLTAGE = 3.2;                 // Battery empty
const float MAX_VOLTAGE = 4.2;                 // Battery full

// Read battery voltage and A0
float readBatteryVoltage(int& rawADC, float& v_adc) {
  rawADC = analogRead(BATTERY_PIN);
  v_adc = (rawADC / 4095.0) * ADC_REF_VOLTAGE * CALIBRATION_FACTOR;
  float batteryVoltage = v_adc * VOLTAGE_DIVIDER_RATIO;
  return batteryVoltage;
}

// Map float
float mapFloat(float x, float in_min, float in_max, float out_min, float out_max) {
  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

// Battery percentage
int calculateBatteryPercentage(float voltage) {
  voltage = constrain(voltage, MIN_VOLTAGE, MAX_VOLTAGE);
  float percent = mapFloat(voltage, MIN_VOLTAGE, MAX_VOLTAGE, 0, 100);
  return (int)percent;
}

void setup() {
  Serial.begin(115200);
  analogReadResolution(12);           // 12-bit ADC
  analogSetAttenuation(ADC_11db);     // Full-scale input ~3.3V
  pinMode(BATTERY_PIN, INPUT);
}

void loop() {
  int rawADC;
  float v_adc;
  float batteryVoltage = readBatteryVoltage(rawADC, v_adc);
  int batteryPercent = calculateBatteryPercentage(batteryVoltage);

  Serial.println("=== Battery Monitor ===");
  Serial.printf("Raw ADC Value: %d\n", rawADC);
  Serial.printf("Voltage at A0: %.3f V\n", v_adc);
  Serial.printf("Battery Voltage: %.3f V\n", batteryVoltage);
  Serial.printf("Battery Percentage: %d%%\n", batteryPercent);
  Serial.println();

  delay(2000); // Update every 2 seconds
}