Battery voltage level back measurement

battery_level.cpp

#include <stdint.h>
#include <stdlib.h>

enum BatteryLevel {
  BATTERY_LEVEL_VERY_LOW = 0,
  BATTERY_LEVEL_LOW = 1,
  BATTERY_LEVEL_MEDIUM = 2,
  BATTERY_LEVEL_HIGH = 3,
  BATTERY_LEVEL_VERY_HIGH = 4,
  BATTERY_LEVEL_END = 5
};

BatteryLevel GetBatteryLevel(BatteryLevel previous_level,
                             int current_voltage_percent) {
  if (current_voltage_percent > 99)
    current_voltage_percent = 99;
  else if (current_voltage_percent < 0)
    current_voltage_percent = 0;

  uint8_t percent_of_each_level = 100 / BATTERY_LEVEL_END;
  uint8_t current_level = current_voltage_percent / percent_of_each_level;

  // Get the median of each level, such as
  // the median of 0 to 19 is 10
  // the median of 20 to 39 is 30...
  uint8_t median_of_previous_level =
      previous_level * percent_of_each_level + (percent_of_each_level / 2);
  if (abs(current_voltage_percent - median_of_previous_level) < percent_of_each_level)
    return (BatteryLevel)previous_level;
  else
    return (BatteryLevel)current_level;
}

BatteryLevel GetBatteryLevel(int current_voltage_percent) {
  static BatteryLevel previous_level = BATTERY_LEVEL_VERY_LOW;
  return previous_level = GetBatteryLevel(previous_level, current_voltage_percent);
}