151 lines
6.2 KiB
Python
151 lines
6.2 KiB
Python
# The MIT License (MIT)
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#
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# Copyright (c) 2017 Carter Nelson for Adafruit Industries
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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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`adafruit_ads1x15.differential`
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====================================================
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Differential driver for ADS1015/1115 ADCs.
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* Author(s): Carter Nelson
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"""
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__version__ = "0.0.0-auto.0"
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__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_ADS1x15.git"
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from .adafruit_ads1x15 import ADS1x15, ADS1X15_DIFF_CHANNELS
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from .adafruit_ads1x15 import ADS1X15_CONFIG_MODE_SINGLE, ADS1X15_CONFIG_MODE_CONTINUOUS
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from .adafruit_ads1x15 import ADS1X15_PGA_RANGE, ADS1015_CONFIG_DR, ADS1115_CONFIG_DR
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# pylint: disable=abstract-method
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class ADS1x15_Differential(ADS1x15):
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"""Base functionality for ADS1x15 analog to digital converters operating
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in differential mode."""
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def __getitem__(self, key):
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return self._channels[ADS1X15_DIFF_CHANNELS[key]]
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def read_adc_difference(self, differential, gain=1, data_rate=None):
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"""Read the difference between two ADC channels and return the ADC value
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as a signed integer result. Differential must be one of:
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- 0 = Channel 0 minus channel 1
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- 1 = Channel 0 minus channel 3
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- 2 = Channel 1 minus channel 3
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- 3 = Channel 2 minus channel 3
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"""
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if not 0 <= differential <= 3:
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raise ValueError('Differential must be a value within 0-3!')
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# Perform a single shot read using the provided differential value
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# as the mux value (which will enable differential mode).
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return self._read(differential, gain, data_rate, ADS1X15_CONFIG_MODE_SINGLE)
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def read_volts_difference(self, differential, gain=1, data_rate=None):
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"""Read the difference between two ADC channels and return the voltage value
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as a floating point result. Differential must be one of:
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- 0 = Channel 0 minus channel 1
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- 1 = Channel 0 minus channel 3
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- 2 = Channel 1 minus channel 3
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- 3 = Channel 2 minus channel 3
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"""
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if not 0 <= differential <= 3:
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raise ValueError('Differential must be a value within 0-3!')
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raw = self.read_adc_difference(differential, gain, data_rate)
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volts = raw * (ADS1X15_PGA_RANGE[gain] / (2**(self.bits-1) - 1))
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return volts
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def start_adc_difference(self, differential, gain=1, data_rate=None):
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"""Start continuous ADC conversions between two ADC channels. Differential
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must be one of:
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- 0 = Channel 0 minus channel 1
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- 1 = Channel 0 minus channel 3
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- 2 = Channel 1 minus channel 3
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- 3 = Channel 2 minus channel 3
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Will return an initial conversion result, then call the get_last_result()
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function continuously to read the most recent conversion result. Call
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stop_adc() to stop conversions.
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"""
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if not 0 <= differential <= 3:
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raise ValueError('Differential must be a value within 0-3!')
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# Perform a single shot read using the provided differential value
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# as the mux value (which will enable differential mode).
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return self._read(differential, gain, data_rate, ADS1X15_CONFIG_MODE_CONTINUOUS)
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# pylint: enable=abstract-method
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class ADS1015(ADS1x15_Differential):
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"""ADS1015 12-bit differential analog to digital converter instance."""
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def __init__(self, *args, **kwargs):
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super(ADS1015, self).__init__(*args, **kwargs)
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self.bits = 12
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def _data_rate_default(self):
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# Default from datasheet page 19, config register DR bit default.
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return 1600
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def _data_rate_config(self, data_rate):
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if data_rate not in ADS1015_CONFIG_DR:
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raise ValueError('Data rate must be one of: 128, 250, 490, 920, 1600, 2400, 3300')
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return ADS1015_CONFIG_DR[data_rate]
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def _conversion_value(self, low, high):
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# Convert to 12-bit signed value.
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value = ((high & 0xFF) << 4) | ((low & 0xFF) >> 4)
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# Check for sign bit and turn into a negative value if set.
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if value & 0x800 != 0:
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value -= 1 << 12
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return value
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def _read_channel(self, channel):
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return self.read_adc_difference(channel)
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def _read_channel_volts(self, channel):
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return self.read_volts_difference(channel)
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class ADS1115(ADS1x15_Differential):
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"""ADS1115 16-bit differential analog to digital converter instance."""
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def __init__(self, *args, **kwargs):
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super(ADS1115, self).__init__(*args, **kwargs)
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self.bits = 16
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def _data_rate_default(self):
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# Default from datasheet page 16, config register DR bit default.
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return 128
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def _data_rate_config(self, data_rate):
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if data_rate not in ADS1115_CONFIG_DR:
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raise ValueError('Data rate must be one of: 8, 16, 32, 64, 128, 250, 475, 860')
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return ADS1115_CONFIG_DR[data_rate]
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def _conversion_value(self, low, high):
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# Convert to 16-bit signed value.
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value = ((high & 0xFF) << 8) | (low & 0xFF)
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# Check for sign bit and turn into a negative value if set.
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if value & 0x8000 != 0:
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value -= 1 << 16
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return value
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def _read_channel(self, channel):
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return self.read_adc_difference(channel)
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def _read_channel_volts(self, channel):
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return self.read_volts_difference(channel)
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