289 lines
9.9 KiB
Python
289 lines
9.9 KiB
Python
# The MIT License (MIT)
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#
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# Copyright (c) 2018 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_bmp3xx`
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====================================================
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CircuitPython driver from BMP3XX Temperature and Barometic Pressure sensor.
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* Author(s): Carter Nelson
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Implementation Notes
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--------------------
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**Hardware:**
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* `Adafruit BMP388 <https://www.adafruit.com/product/3966>`_
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**Software and Dependencies:**
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* Adafruit CircuitPython firmware for the supported boards:
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https://github.com/adafruit/circuitpython/releases
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# * Adafruit's Bus Device library: https://github.com/adafruit/Adafruit_CircuitPython_BusDevice
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"""
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import time
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try:
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import struct
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except ImportError:
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import ustruct as struct
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from micropython import const
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__version__ = "0.0.0-auto.0"
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__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_BMP3XX.git"
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_CHIP_ID = const(0x50)
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# pylint: disable=import-outside-toplevel
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_REGISTER_CHIPID = const(0x00)
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_REGISTER_STATUS = const(0x03)
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_REGISTER_PRESSUREDATA = const(0x04)
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_REGISTER_TEMPDATA = const(0x07)
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_REGISTER_CONTROL = const(0x1B)
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_REGISTER_OSR = const(0x1C)
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_REGISTER_ODR = const(0x1D)
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_REGISTER_CONFIG = const(0x1F)
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_REGISTER_CAL_DATA = const(0x31)
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_REGISTER_CMD = const(0x7E)
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# pylint: enable=bad-whitespace
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_OSR_SETTINGS = (1, 2, 4, 8, 16, 32) # pressure and temperature oversampling settings
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_IIR_SETTINGS = (0, 2, 4, 8, 16, 32, 64, 128) # IIR filter coefficients
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class BMP3XX:
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"""Base class for BMP3XX sensor."""
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def __init__(self):
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chip_id = self._read_byte(_REGISTER_CHIPID)
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if _CHIP_ID != chip_id:
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raise RuntimeError("Failed to find BMP3XX! Chip ID 0x%x" % chip_id)
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self._read_coefficients()
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self.reset()
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self.sea_level_pressure = 1013.25
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"""Sea level pressure in hPa."""
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@property
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def pressure(self):
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"""The pressure in hPa."""
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return self._read()[0] / 100
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@property
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def temperature(self):
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"""The temperature in deg C."""
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return self._read()[1]
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@property
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def altitude(self):
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"""The altitude in meters based on the currently set sea level pressure."""
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# see https://www.weather.gov/media/epz/wxcalc/pressureAltitude.pdf
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return 44307.7 * (1 - (self.pressure / self.sea_level_pressure) ** 0.190284)
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@property
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def pressure_oversampling(self):
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"""The pressure oversampling setting."""
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return _OSR_SETTINGS[self._read_byte(_REGISTER_OSR) & 0x07]
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@pressure_oversampling.setter
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def pressure_oversampling(self, oversample):
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if oversample not in _OSR_SETTINGS:
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raise ValueError("Oversampling must be one of: {}".format(_OSR_SETTINGS))
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new_setting = self._read_byte(_REGISTER_OSR) & 0xF8 | _OSR_SETTINGS.index(
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oversample
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)
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self._write_register_byte(_REGISTER_OSR, new_setting)
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@property
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def temperature_oversampling(self):
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"""The temperature oversampling setting."""
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return _OSR_SETTINGS[self._read_byte(_REGISTER_OSR) >> 3 & 0x07]
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@temperature_oversampling.setter
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def temperature_oversampling(self, oversample):
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if oversample not in _OSR_SETTINGS:
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raise ValueError("Oversampling must be one of: {}".format(_OSR_SETTINGS))
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new_setting = (
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self._read_byte(_REGISTER_OSR) & 0xC7 | _OSR_SETTINGS.index(oversample) << 3
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)
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self._write_register_byte(_REGISTER_OSR, new_setting)
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@property
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def filter_coefficient(self):
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"""The IIR filter coefficient."""
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return _IIR_SETTINGS[self._read_byte(_REGISTER_CONFIG) >> 1 & 0x07]
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@filter_coefficient.setter
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def filter_coefficient(self, coef):
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if coef not in _IIR_SETTINGS:
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raise ValueError(
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"Filter coefficient must be one of: {}".format(_IIR_SETTINGS)
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)
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self._write_register_byte(_REGISTER_CONFIG, _IIR_SETTINGS.index(coef) << 1)
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def reset(self):
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"""Perform a power on reset. All user configuration settings are overwritten
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with their default state.
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"""
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self._write_register_byte(_REGISTER_CMD, 0xB6)
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def _read(self):
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"""Returns a tuple for temperature and pressure."""
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# OK, pylint. This one is all kinds of stuff you shouldn't worry about.
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# pylint: disable=bad-whitespace, invalid-name, too-many-locals
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# Perform one measurement in forced mode
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self._write_register_byte(_REGISTER_CONTROL, 0x13)
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# Wait for *both* conversions to complete
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while self._read_byte(_REGISTER_STATUS) & 0x60 != 0x60:
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time.sleep(0.002)
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# Get ADC values
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data = self._read_register(_REGISTER_PRESSUREDATA, 6)
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adc_p = data[2] << 16 | data[1] << 8 | data[0]
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adc_t = data[5] << 16 | data[4] << 8 | data[3]
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# datasheet, sec 9.2 Temperature compensation
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T1, T2, T3 = self._temp_calib
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pd1 = adc_t - T1
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pd2 = pd1 * T2
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temperature = pd2 + (pd1 * pd1) * T3
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# datasheet, sec 9.3 Pressure compensation
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P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, P11 = self._pressure_calib
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pd1 = P6 * temperature
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pd2 = P7 * temperature ** 2.0
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pd3 = P8 * temperature ** 3.0
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po1 = P5 + pd1 + pd2 + pd3
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pd1 = P2 * temperature
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pd2 = P3 * temperature ** 2.0
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pd3 = P4 * temperature ** 3.0
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po2 = adc_p * (P1 + pd1 + pd2 + pd3)
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pd1 = adc_p ** 2.0
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pd2 = P9 + P10 * temperature
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pd3 = pd1 * pd2
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pd4 = pd3 + P11 * adc_p ** 3.0
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pressure = po1 + po2 + pd4
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# pressure in Pa, temperature in deg C
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return pressure, temperature
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def _read_coefficients(self):
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# pylint: disable=bad-whitespace, bad-continuation
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"""Read & save the calibration coefficients"""
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coeff = self._read_register(_REGISTER_CAL_DATA, 21)
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# See datasheet, pg. 27, table 22
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coeff = struct.unpack("<HHbhhbbHHbbhbb", coeff)
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# See datasheet, sec 9.1
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# Note: forcing float math to prevent issues with boards that
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# do not support long ints for 2**<large int>
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self._temp_calib = (
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coeff[0] / 2 ** -8.0, # T1
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coeff[1] / 2 ** 30.0, # T2
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coeff[2] / 2 ** 48.0,
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) # T3
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self._pressure_calib = (
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(coeff[3] - 2 ** 14.0) / 2 ** 20.0, # P1
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(coeff[4] - 2 ** 14.0) / 2 ** 29.0, # P2
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coeff[5] / 2 ** 32.0, # P3
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coeff[6] / 2 ** 37.0, # P4
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coeff[7] / 2 ** -3.0, # P5
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coeff[8] / 2 ** 6.0, # P6
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coeff[9] / 2 ** 8.0, # P7
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coeff[10] / 2 ** 15.0, # P8
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coeff[11] / 2 ** 48.0, # P9
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coeff[12] / 2 ** 48.0, # P10
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coeff[13] / 2 ** 65.0,
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) # P11
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def _read_byte(self, register):
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"""Read a byte register value and return it"""
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return self._read_register(register, 1)[0]
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def _read_register(self, register, length):
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"""Low level register reading, not implemented in base class"""
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raise NotImplementedError()
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def _write_register_byte(self, register, value):
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"""Low level register writing, not implemented in base class"""
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raise NotImplementedError()
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class BMP3XX_I2C(BMP3XX):
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"""Driver for I2C connected BMP3XX. Default address is 0x77 but another address can be passed
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in as an argument"""
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def __init__(self, i2c, address=0x77):
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import adafruit_bus_device.i2c_device as i2c_device
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self._i2c = i2c_device.I2CDevice(i2c, address)
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super().__init__()
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def _read_register(self, register, length):
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"""Low level register reading over I2C, returns a list of values"""
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result = bytearray(length)
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with self._i2c as i2c:
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i2c.write(bytes([register & 0xFF]))
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i2c.readinto(result)
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return result
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def _write_register_byte(self, register, value):
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"""Low level register writing over I2C, writes one 8-bit value"""
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with self._i2c as i2c:
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i2c.write(bytes((register & 0xFF, value & 0xFF)))
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class BMP3XX_SPI(BMP3XX):
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"""Driver for SPI connected BMP3XX."""
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def __init__(self, spi, cs):
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import adafruit_bus_device.spi_device as spi_device
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self._spi = spi_device.SPIDevice(spi, cs)
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# toggle CS low/high to put BMP3XX in SPI mode
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with self._spi:
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time.sleep(0.001)
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super().__init__()
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def _read_register(self, register, length):
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"""Low level register reading over SPI, returns a list of values"""
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result = bytearray(length)
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with self._spi as spi:
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# pylint: disable=no-member
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spi.write(bytes((0x80 | register, 0x00)))
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spi.readinto(result)
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return result
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def _write_register_byte(self, register, value):
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"""Low level register writing over SPI, writes one 8-bit value"""
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with self._spi as spi:
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# pylint: disable=no-member
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spi.write(bytes((register & 0x7F, value & 0xFF)))
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