Custom battery monitoring using calibrated ADC values instead of pangodream library

platformio.ini

@@ -16,7 +16,6 @@ board_build.partitions = default_16MB.csv
 ; Libraries
 lib_deps =
     zinggjm/GxEPD2@^1.5.9
-    https://github.com/pangodream/18650CL
 
 ; Build flags
 build_flags = 

src/BatteryMonitor.cpp

@@ -0,0 +1,54 @@
+// BatteryMonitor.cpp
+#include "BatteryMonitor.h"
+#include "esp_adc_cal.h"
+
+BatteryMonitor::BatteryMonitor(uint8_t adcPin, float dividerMultiplier)
+  : _adcPin(adcPin), _dividerMultiplier(dividerMultiplier)
+{
+}
+
+uint16_t BatteryMonitor::readPercentage() const
+{
+  return percentageFromMillivolts(readMillivolts());
+}
+
+uint16_t BatteryMonitor::readMillivolts() const
+{
+  const uint16_t raw = readRawMillivolts();
+  const uint32_t mv = millivoltsFromRawAdc(raw);
+  return static_cast<uint32_t>(mv * _dividerMultiplier);
+}
+
+uint16_t BatteryMonitor::readRawMillivolts() const
+{
+  const uint16_t raw = analogRead(_adcPin);
+  return raw;
+}
+
+double BatteryMonitor::readVolts() const
+{
+  return static_cast<double>(readMillivolts()) / 1000.0;
+}
+
+uint16_t BatteryMonitor::percentageFromMillivolts(uint16_t millivolts)
+{
+  double volts = millivolts / 1000.0;
+  // Polynomial derived from LiPo samples
+  double y = -144.9390 * volts * volts * volts +
+             1655.8629 * volts * volts -
+             6158.8520 * volts +
+             7501.3202;
+
+  // Clamp to [0,100] and round
+  y = max(y, 0.0);
+  y = min(y, 100.0);
+  y = round(y);
+  return static_cast<int>(y);
+}
+
+uint16_t BatteryMonitor::millivoltsFromRawAdc(uint16_t adc_raw)
+{
+  esp_adc_cal_characteristics_t adc_chars;
+  esp_adc_cal_characterize(ADC_UNIT_1, ADC_ATTEN_DB_12, ADC_WIDTH_BIT_12, 1100, &adc_chars);
+  return esp_adc_cal_raw_to_voltage(adc_raw, &adc_chars);
+}

src/BatteryMonitor.h

@@ -0,0 +1,33 @@
+// BatteryMonitor.h
+#pragma once
+
+#include <Arduino.h>
+
+class BatteryMonitor
+{
+public:
+  // Optional divider multiplier parameter defaults to 2.0
+  explicit BatteryMonitor(uint8_t adcPin, float dividerMultiplier = 2.0f);
+
+  // Read voltage and return percentage (0-100)
+  uint16_t readPercentage() const;
+
+  // Read the battery voltage in millivolts (accounts for divider)
+  uint16_t readMillivolts() const;
+  
+  // Read raw millivolts from ADC (doesn't account for divider)
+  uint16_t readRawMillivolts() const;
+
+  // Read the battery voltage in volts (accounts for divider)
+  double readVolts() const;
+
+  // Percentage (0-100) from a millivolt value
+  static uint16_t percentageFromMillivolts(uint16_t millivolts);
+
+  // Calibrate a raw ADC reading and return millivolts
+  static uint16_t millivoltsFromRawAdc(uint16_t adc_raw);
+
+private:
+  uint8_t _adcPin;
+  float _dividerMultiplier;
+};

src/main.cpp

@@ -4,7 +4,7 @@
 #include <GxEPD2_BW.h>
 #include <SPI.h>
 #include "image.h"
-#include "Pangodream_18650_CL.h"
+#include "BatteryMonitor.h"
 
 // Display SPI pins (custom pins for XteinkX4, not hardware SPI defaults)
 #define EPD_SCLK 8  // SPI Clock
@@ -20,12 +20,9 @@
 #define BTN_GPIO3 3 // Power button (digital)
 
 #define UART0_RXD 20 // Used for USB connection detection
-
 #define BAT_GPIO0 0 // Battery voltage
-#define READS 10
-#define CONV_FACTOR 1.5176
 
-Pangodream_18650_CL BL(BAT_GPIO0, CONV_FACTOR, READS);
+static BatteryMonitor g_battery(BAT_GPIO0);
 
 static int rawBat = 0;
 
@@ -44,7 +41,7 @@ volatile DisplayCommand displayCommand = DISPLAY_NONE;
 // GxEPD2 display - Using GxEPD2_426_GDEQ0426T82
 // Note: XteinkX4 has 4.26" 800x480 display
 GxEPD2_BW<GxEPD2_426_GDEQ0426T82, GxEPD2_426_GDEQ0426T82::HEIGHT> display(
-    GxEPD2_426_GDEQ0426T82(EPD_CS, EPD_DC, EPD_RST, EPD_BUSY));
+  GxEPD2_426_GDEQ0426T82(EPD_CS, EPD_DC, EPD_RST, EPD_BUSY));
 
 // FreeRTOS task for non-blocking display updates
 TaskHandle_t displayTaskHandle = NULL;
@@ -78,6 +75,7 @@ volatile Button currentPressedButton = NONE;
 const unsigned long POWER_BUTTON_WAKEUP_MS = 1000; // Time required to confirm boot from sleep
 const unsigned long POWER_BUTTON_SLEEP_MS = 1000;  // Time required to enter sleep mode
 
+
 // Get button name as string
 const char *getButtonName(Button btn)
 {
@@ -163,11 +161,11 @@ void drawBatteryInfo()
   display.printf("Power: %s", charging ? "Charging" : "Battery");
 
   display.setCursor(40, 200);
-  display.printf("Raw: %i", rawBat);
+  display.printf("Raw: %i", g_battery.readRawMillivolts());
   display.setCursor(40, 240);
-  display.printf("Volts: %.2f V", BL.getBatteryVolts());
+  display.printf("Volts: %.2f V", g_battery.readVolts());
   display.setCursor(40, 280);
-  display.printf("Charge: %i%%", BL.getBatteryChargeLevel());
+  display.printf("Charge: %i%%", g_battery.readPercentage());
 }
 
 // Display update task running on separate core
@@ -410,14 +408,14 @@ void loop()
 
     Serial.println("");
 
-    Serial.print("Value from pin: ");
-    Serial.println(rawBat);
-    Serial.print("Average value from pin: ");
-    Serial.println(BL.pinRead());
+    Serial.print("Value from pin (raw/calibrated): ");
+    Serial.print(rawBat);
+    Serial.print(" / ");
+    Serial.println(BatteryMonitor::millivoltsFromRawAdc(rawBat));
     Serial.print("Volts: ");
-    Serial.println(BL.getBatteryVolts());
+    Serial.println(g_battery.readVolts());
     Serial.print("Charge level: ");
-    Serial.println(BL.getBatteryChargeLevel());
+    Serial.println(g_battery.readPercentage());
     Serial.println("");
     lastLogMs = now;
   }