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