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