# SPDX-FileCopyrightText: 2018 Carter Nelson for Adafruit Industries
#
# SPDX-License-Identifier: MIT
"""
`analog_in`
==============================
AnalogIn for single-ended and
differential ADC readings.
* Author(s): Carter Nelson, adapted from MCP3xxx original by Brent Rubell
"""
try:
from typing import Optional
from .ads1x15 import ADS1x15
except ImportError:
pass
_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}
[docs]
class AnalogIn:
"""AnalogIn Mock Implementation for ADC Reads.
:param ADS1x15 ads: The ads object.
:param int positive_pin: Required pin for single-ended.
:param int negative_pin: Optional pin for differential reads.
"""
def __init__(self, ads: ADS1x15, positive_pin: int, negative_pin: Optional[int] = None):
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(
f"Differential channels must be one of: {list(_ADS1X15_DIFF_CHANNELS.keys())}"
)
self._pin_setting = _ADS1X15_DIFF_CHANNELS[pins]
self.is_differential = True
@property
def value(self) -> int:
"""The value on the analog pin between 0 and 65535
inclusive (16-bit). (read-only)
Even if the underlying analog to digital converter (ADC) is
lower resolution, the value is 16-bit.
"""
pin = self._pin_setting if self.is_differential else self._pin_setting + 0x04
return self._ads.read(pin)
@property
def voltage(self) -> float:
"""Returns the voltage from the ADC pin as a floating point value."""
volts = self.convert_to_voltage(self.value)
return volts
[docs]
def convert_to_value(self, volts: float) -> int:
"""Calculates a standard 16-bit integer value for a given voltage"""
lsb = _ADS1X15_PGA_RANGE[self._ads.gain] / (1 << (self._ads.bits - 1))
value = int(volts / lsb)
# Need to bit shift if value is only 12-bits
value <<= 16 - self._ads.bits
return value
[docs]
def convert_to_voltage(self, value_int: int) -> float:
"""Calculates voltage from 16-bit ADC reading"""
lsb = _ADS1X15_PGA_RANGE[self._ads.gain] / (1 << (self._ads.bits - 1))
# Need to bit shift if value is only 12-bits
value_int >>= 16 - self._ads.bits
volts = value_int * lsb
return volts