# The MIT License (MIT)
#
# Copyright (c) 2018 Carter Nelson for Adafruit Industries
#
# 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
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
"""
`ads1x15`
====================================================
CircuitPython base class driver for ADS1015/1115 ADCs.
* Author(s): Carter Nelson
"""
__version__ = "0.0.0-auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_ADS1x15.git"
import time
from micropython import const
from adafruit_bus_device.i2c_device import I2CDevice
# pylint: disable=bad-whitespace
_ADS1X15_DEFAULT_ADDRESS = const(0x48)
_ADS1X15_POINTER_CONVERSION = const(0x00)
_ADS1X15_POINTER_CONFIG = const(0x01)
_ADS1X15_CONFIG_OS_SINGLE = const(0x8000)
_ADS1X15_CONFIG_MUX_OFFSET = const(12)
_ADS1X15_CONFIG_COMP_QUE_DISABLE = const(0x0003)
_ADS1X15_CONFIG_GAIN = {
2/3: 0x0000,
1: 0x0200,
2: 0x0400,
4: 0x0600,
8: 0x0800,
16: 0x0A00
}
# pylint: enable=bad-whitespace
[docs]class Mode:
"""An enum-like class representing possible ADC operating modes."""
# See datasheet "Operating Modes" section
# values here are masks for setting MODE bit in Config Register
#pylint: disable=too-few-public-methods
CONTINUOUS = 0x0000
SINGLE = 0x0100
[docs]class ADS1x15(object):
"""Base functionality for ADS1x15 analog to digital converters."""
def __init__(self, i2c, gain=1, data_rate=None, mode=Mode.SINGLE,
address=_ADS1X15_DEFAULT_ADDRESS):
#pylint: disable=too-many-arguments
self.buf = bytearray(3)
self._data_rate = self._gain = self._mode = None
self.gain = gain
self.data_rate = self._data_rate_default() if data_rate is None else data_rate
self.mode = mode
self.i2c_device = I2CDevice(i2c, address)
@property
def data_rate(self):
"""The data rate for ADC conversion in samples per second."""
return self._data_rate
@data_rate.setter
def data_rate(self, rate):
possible_rates = self.rates
if rate not in possible_rates:
raise ValueError("Data rate must be one of: {}".format(possible_rates))
self._data_rate = rate
@property
def rates(self):
"""Possible data rate settings."""
raise NotImplementedError('Subclass must implement rates property.')
@property
def rate_config(self):
"""Rate configuration masks."""
raise NotImplementedError('Subclass must implement rate_config property.')
@property
def gain(self):
"""The ADC gain."""
return self._gain
@gain.setter
def gain(self, gain):
possible_gains = self.gains
if gain not in possible_gains:
raise ValueError("Gain must be one of: {}".format(possible_gains))
self._gain = gain
@property
def gains(self):
"""Possible gain settings."""
g = list(_ADS1X15_CONFIG_GAIN.keys())
g.sort()
return g
@property
def mode(self):
"""The ADC conversion mode."""
return self._mode
@mode.setter
def mode(self, mode):
if mode != Mode.CONTINUOUS and mode != Mode.SINGLE:
raise ValueError("Unsupported mode.")
self._mode = mode
[docs] def read(self, pin, is_differential=False):
"""I2C Interface for ADS1x15-based ADCs reads.
params:
:param pin: individual or differential pin.
:param bool is_differential: single-ended or differential read.
"""
pin = pin if is_differential else pin + 0x04
return self._read(pin)
def _data_rate_default(self):
"""Retrieve the default data rate for this ADC (in samples per second).
Should be implemented by subclasses.
"""
raise NotImplementedError('Subclasses must implement _data_rate_default!')
def _conversion_value(self, raw_adc):
"""Subclasses should override this function that takes the 16 raw ADC
values of a conversion result and returns a signed integer value.
"""
raise NotImplementedError('Subclass must implement _conversion_value function!')
def _read(self, pin):
"""Perform an ADC read. Returns the signed integer result of the read."""
config = _ADS1X15_CONFIG_OS_SINGLE
config |= (pin & 0x07) << _ADS1X15_CONFIG_MUX_OFFSET
config |= _ADS1X15_CONFIG_GAIN[self.gain]
config |= self.mode
config |= self.rate_config[self.data_rate]
config |= _ADS1X15_CONFIG_COMP_QUE_DISABLE
self._write_register(_ADS1X15_POINTER_CONFIG, config)
while not self._conversion_complete():
time.sleep(0.01)
return self.get_last_result()
def _conversion_complete(self):
"""Return status of ADC conversion."""
# OS is bit 15
# OS = 0: Device is currently performing a conversion
# OS = 1: Device is not currently performing a conversion
return self._read_register(_ADS1X15_POINTER_CONFIG) & 0x8000
[docs] def get_last_result(self):
"""Read the last conversion result when in continuous conversion mode.
Will return a signed integer value.
"""
return self._conversion_value(self._read_register(_ADS1X15_POINTER_CONVERSION))
def _write_register(self, reg, value):
"""Write 16 bit value to register."""
self.buf[0] = reg
self.buf[1] = (value >> 8) & 0xFF
self.buf[2] = value & 0xFF
with self.i2c_device as i2c:
i2c.write(self.buf)
def _read_register(self, reg):
"""Read 16 bit register value."""
self.buf[0] = reg
with self.i2c_device as i2c:
i2c.write(self.buf, end=1, stop=False)
i2c.readinto(self.buf, end=2)
return self.buf[0] << 8 | self.buf[1]