class CurrentSensor:
    """
    Converts an analog current with a resistor to a scaled unit, which was read by an ADC.

    The maximum analog voltage is defined with the resistor.
    At 20mA, a voltage drop of 3.2V occurs across a 160 Ω resistor.

    The lower_unit and upper_unit is to scale the unit.

    The order of conversion:
      1) current out from sensor e.G: 4mA - 20mA
      2) resistor to have a voltage drop. U = R * I
      3) raw_value from ADC what the microcontroller reads
      4) calculatig the voltage from raw_value
      5) calculating the current from voltage
      6) normalized value 0-1 from current
      7) scaled unit from normalized value
    """

    def __init__(
        self,
        bits=12,
        lower_current=0.004,
        upper_current=0.02,
        ref_voltage=3.3,
        resistor=160,
        lower_unit=0,
        upper_unit=100,
    ):
        self.bits = bits
        self.lower_current = lower_current
        self.upper_current = upper_current
        self.ref_voltage = ref_voltage
        self.resistor = resistor
        self.lower_unit = lower_unit
        self.upper_unit = upper_unit

    @property
    def delta_current(self):
        return self.upper_current - self.lower_current

    @property
    def delta_unit(self):
        return self.upper_unit - self.lower_unit

    @property
    def increments(self):
        return 2**self.bits - 1

    def convert(self, raw_value) -> float:
        """
        Return a scaled unit
        """
        voltage = raw_value / self.increments * self.ref_voltage
        current = voltage / self.resistor
        norm = (current - self.lower_current) / self.delta_current
        return norm * self.delta_unit + self.lower_unit