1  # SPDX-FileCopyrightText: Copyright (c) 2020 Bryan Siepert for Adafruit Industries
 2  #
 3  # SPDX-License-Identifier: MIT
 4  
 5  # Permission is hereby granted, free of charge, to any person obtaining a copy
 6  # of this software and associated documentation files (the "Software"), to deal
 7  # in the Software without restriction, including without limitation the rights
 8  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 9  # copies of the Software, and to permit persons to whom the Software is
10  # furnished to do so, subject to the following conditions:
11  #
12  # The above copyright notice and this permission notice shall be included in
13  # all copies or substantial portions of the Software.
14  #
15  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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21  # THE SOFTWARE.
22  """
23  `analog_in`
24  ==============================
25  AnalogIn for ADC readings.
26  
27  * Author(s): Bryan Siepert, adpted from ADS1x15 by Carter Nelson
28  """
29  
30  
31  class AnalogIn:
32      """AnalogIn Mock Implementation for ADC Reads."""
33  
34      def __init__(self, pcf, pin):
35          """AnalogIn
36  
37          :param ads: The PCF8591 object.
38          :param ~digitalio.DigitalInOut pin: Required ADC channel pin.
39  
40          """
41          self._pcf = pcf
42          self._channel_number = pin
43  
44      @property
45      def voltage(self):
46          """Returns the value of an ADC channel in volts as compared to the reference voltage."""
47  
48          if not self._pcf:
49              raise RuntimeError(
50                  "Underlying ADC does not exist, likely due to callint `deinit`"
51              )
52          raw_reading = self._pcf.read(self._channel_number)
53          return ((raw_reading << 8) / 65535) * self._pcf.reference_voltage
54  
55      @property
56      def value(self):
57          """Returns the value of an ADC channel.
58          The value is scaled to a 16-bit integer from the native 8-bit value."""
59  
60          if not self._pcf:
61              raise RuntimeError(
62                  "Underlying ADC does not exist, likely due to callint `deinit`"
63              )
64  
65          return self._pcf.read(self._channel_number) << 8
66  
67      @property
68      def reference_voltage(self):
69          """The maximum voltage measurable (also known as the reference voltage) as a float in
70          Volts. Assumed to be 3.3V but can be overridden using the `PCF8591` constructor"""
71          if not self._pcf:
72              raise RuntimeError(
73                  "Underlying ADC does not exist, likely due to callint `deinit`"
74              )
75          return self._pcf.reference_voltage
76  
77      def deinit(self):
78          """Release the reference to the PCF8591. Create a new AnalogIn to use it again."""
79          self._pcf = None