73 lines
2.9 KiB
Python
73 lines
2.9 KiB
Python
# The MIT License (MIT)
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#
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# Copyright (c) 2018 Carter Nelson for Adafruit
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in
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# all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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# THE SOFTWARE.
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"""
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`analog_in`
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==============================
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AnalogIn for single-ended and
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differential ADC readings.
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* Author(s): Carter Nelson, adapted from MCP3xxx original by Brent Rubell
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"""
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# pylint: disable=bad-whitespace
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_ADS1X15_DIFF_CHANNELS = {(0, 1): 0, (0, 3): 1, (1, 3): 2, (2, 3): 3}
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_ADS1X15_PGA_RANGE = {2 / 3: 6.144, 1: 4.096, 2: 2.048, 4: 1.024, 8: 0.512, 16: 0.256}
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# pylint: enable=bad-whitespace
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class AnalogIn:
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"""AnalogIn Mock Implementation for ADC Reads."""
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def __init__(self, ads, positive_pin, negative_pin=None):
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"""AnalogIn
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:param ads: The ads object.
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:param ~digitalio.DigitalInOut positive_pin: Required pin for single-ended.
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:param ~digitalio.DigitalInOut negative_pin: Optional pin for differential reads.
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"""
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self._ads = ads
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self._pin_setting = positive_pin
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self._negative_pin = negative_pin
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self.is_differential = False
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if negative_pin is not None:
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pins = (self._pin_setting, self._negative_pin)
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if pins not in _ADS1X15_DIFF_CHANNELS:
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raise ValueError(
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"Differential channels must be one of: {}".format(
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list(_ADS1X15_DIFF_CHANNELS.keys())
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)
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)
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self._pin_setting = _ADS1X15_DIFF_CHANNELS[pins]
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self.is_differential = True
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@property
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def value(self):
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"""Returns the value of an ADC pin as an integer."""
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return self._ads.read(
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self._pin_setting, is_differential=self.is_differential
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) << (16 - self._ads.bits)
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@property
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def voltage(self):
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"""Returns the voltage from the ADC pin as a floating point value."""
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volts = self.value * _ADS1X15_PGA_RANGE[self._ads.gain] / 32767
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return volts
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