Add MAX17048 lipo fuel gauge (#4851)

* Initial commit

* Update MAX17048Sensor.cpp

* Update EnvironmentTelemetry.cpp

---------

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

src/modules/Telemetry/Sensor/MAX17048Sensor.h

@@ -0,0 +1,110 @@
+#pragma once
+
+#ifndef MAX17048_SENSOR_H
+#define MAX17048_SENSOR_H
+
+#include "configuration.h"
+
+#if !MESHTASTIC_EXCLUDE_I2C && !defined(ARCH_PORTDUINO) && !defined(ARCH_STM32WL)
+
+// Samples to store in a buffer to determine if the battery is charging or discharging
+#define MAX17048_CHARGING_SAMPLES 3
+
+// Threshold to determine if the battery is on charge, in percent/hour
+#define MAX17048_CHARGING_MINIMUM_RATE 1.0f
+
+// Threshold to determine if the board has bus power
+#define MAX17048_BUS_POWER_VOLTS 4.195f
+
+#include "../mesh/generated/meshtastic/telemetry.pb.h"
+#include "TelemetrySensor.h"
+#include "VoltageSensor.h"
+
+#include "meshUtils.h"
+#include <Adafruit_MAX1704X.h>
+#include <queue>
+
+struct MAX17048ChargeSample {
+    float cellPercent;
+    float chargeRate;
+};
+
+enum MAX17048ChargeState { IDLE, EXPORT, IMPORT };
+
+// Singleton wrapper for the Adafruit_MAX17048 class
+class MAX17048Singleton : public Adafruit_MAX17048
+{
+  private:
+    static MAX17048Singleton *pinstance;
+    bool initialized = false;
+    std::queue<MAX17048ChargeSample> chargeSamples;
+    MAX17048ChargeState chargeState = IDLE;
+    const String chargeLabels[3] = {F("idle"), F("export"), F("import")};
+
+  protected:
+    MAX17048Singleton();
+    ~MAX17048Singleton();
+
+  public:
+    // Create a singleton instance (not thread safe)
+    static MAX17048Singleton *GetInstance();
+
+    // Singletons should not be cloneable.
+    MAX17048Singleton(MAX17048Singleton &other) = delete;
+
+    // Singletons should not be assignable.
+    void operator=(const MAX17048Singleton &) = delete;
+
+    // Initialise the sensor (not thread safe)
+    virtual bool runOnce(TwoWire *theWire = &Wire);
+
+    // Get the current bus voltage
+    uint16_t getBusVoltageMv();
+
+    // Get the state of charge in percent 0 to 100
+    uint8_t getBusBatteryPercent();
+
+    // Calculate the seconds to charge/discharge
+    uint16_t getTimeToGoSecs();
+
+    // Returns true if the battery sensor has started
+    inline virtual bool isInitialised() { return initialized; };
+
+    // Returns true if the battery is currently on charge (not thread safe)
+    bool isBatteryCharging();
+
+    // Returns true if a battery is actually connected
+    bool isBatteryConnected();
+
+    // Returns true if there is bus or external power connected
+    bool isExternallyPowered();
+};
+
+#if (HAS_TELEMETRY && (!MESHTASTIC_EXCLUDE_ENVIRONMENTAL_SENSOR || !MESHTASTIC_EXCLUDE_POWER_TELEMETRY))
+
+class MAX17048Sensor : public TelemetrySensor, VoltageSensor
+{
+  private:
+    MAX17048Singleton *max17048 = nullptr;
+
+  protected:
+    virtual void setup() override;
+
+  public:
+    MAX17048Sensor();
+
+    // Initialise the sensor
+    virtual int32_t runOnce() override;
+
+    // Get the current bus voltage and state of charge
+    virtual bool getMetrics(meshtastic_Telemetry *measurement) override;
+
+    // Get the current bus voltage
+    virtual uint16_t getBusVoltageMv() override;
+};
+
+#endif
+
+#endif
+
+#endif