InfiniTime/src/components/battery/BatteryController.h

#pragma once
#include <cstdint>
#include <drivers/include/nrfx_saadc.h>
#include <array>
#include <numeric>

namespace Pinetime {
  namespace Controllers {

    /** A simple circular buffer that can be used to average 
     out the sensor values. The total capacity of the CircBuffer  
    is given as the template parameter N.
    */ 
    template <int N> 
    class CircBuffer {
    public:
      CircBuffer() : arr{}, sz{}, cap{N}, head{} {}
      /**
     insert member function overwrites the next data to the current 
    HEAD and moves the HEAD to the newly inserted value.
    */ 
      void insert(const int num) {
        head %= cap;
        arr[head++] = num;
        if (sz != cap) {
          sz++;
        }
      }

      int GetAverage() const {
        int sum = std::accumulate(arr.begin(), arr.end(), 0);
        return (sum / sz);
      }

    private:
      std::array<int, N> arr; /**< internal array used to store the values*/
      uint8_t sz; /**< The current size of the array.*/
      uint8_t cap; /**< Total capacity of the CircBuffer.*/
      uint8_t head; /**< The current head of the CircBuffer*/
    };

    class Battery {
      public:

        Battery();

        void Init();
        void Update();
        
        int PercentRemaining() const { return percentRemainingBuffer.GetAverage(); }

        float Voltage() const { return voltage; }

        bool IsCharging() const { return isCharging; }
        bool IsPowerPresent() const { return isPowerPresent; }        

      private:
        static Battery *instance;
        nrf_saadc_value_t  saadc_value;
        
        static constexpr uint8_t percentRemainingSamples = 5;
        CircBuffer<percentRemainingSamples> percentRemainingBuffer {};

        static constexpr uint32_t chargingPin = 12;
        static constexpr uint32_t powerPresentPin = 19;
        static constexpr nrf_saadc_input_t batteryVoltageAdcInput = NRF_SAADC_INPUT_AIN7;
        float voltage = 0.0f;
        int percentRemaining = -1;

        bool isCharging = false;
        bool isPowerPresent = false;
        
        void SaadcInit();

        void SaadcEventHandler(nrfx_saadc_evt_t const * p_event);
        static void adcCallbackStatic(nrfx_saadc_evt_t const *event);

        bool isReading = false;
        uint8_t samples = 0;
    };
  }
}