Merge pull request #13 from jraber/master

Adopt changes from the BME280 library

Author: makermelissa

adafruit_bmp280.py

@@ -20,20 +20,19 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 # THE SOFTWARE.
 """
-`adafruit_bmp280`
-====================================================
+`adafruit_bmp280` - Adafruit BMP280 - Temperature & Barometic Pressure Sensor
+===============================================================================
 
 CircuitPython driver from BMP280 Temperature and Barometic Pressure sensor
 
 * Author(s): ladyada
 """
 import math
-import time
+from time import sleep
 try:
     import struct
 except ImportError:
     import ustruct as struct
-
 from micropython import const
 
 __version__ = "0.0.0-auto.0"
@@ -45,24 +44,61 @@
 
 _REGISTER_CHIPID = const(0xD0)
 _REGISTER_DIG_T1 = const(0x88)
-# _REGISTER_DIG_T2 = const(0x8A)
-# _REGISTER_DIG_T3 = const(0x8C)
-# _REGISTER_DIG_P1 = const(0x8E)
-# _REGISTER_DIG_P2 = const(0x90)
-# _REGISTER_DIG_P3 = const(0x92)
-# _REGISTER_DIG_P4 = const(0x94)
-# _REGISTER_DIG_P5 = const(0x96)
-# _REGISTER_DIG_P6 = const(0x98)
-# _REGISTER_DIG_P7 = const(0x9A)
-# _REGISTER_DIG_P8 = const(0x9C)
-# _REGISTER_DIG_P9 = const(0x9E)
 _REGISTER_SOFTRESET = const(0xE0)
 _REGISTER_STATUS = const(0xF3)
-_REGISTER_CONTROL = const(0xF4)
+_REGISTER_CTRL_MEAS = const(0xF4)
 _REGISTER_CONFIG = const(0xF5)
 _REGISTER_PRESSUREDATA = const(0xF7)
 _REGISTER_TEMPDATA = const(0xFA)
 
+_BMP280_PRESSURE_MIN_HPA = const(300)
+_BMP280_PRESSURE_MAX_HPA = const(1100)
+
+
+"""iir_filter values"""
+IIR_FILTER_DISABLE = const(0)
+IIR_FILTER_X2 = const(0x01)
+IIR_FILTER_X4 = const(0x02)
+IIR_FILTER_X8 = const(0x03)
+IIR_FILTER_X16 = const(0x04)
+
+_BMP280_IIR_FILTERS = frozenset((IIR_FILTER_DISABLE, IIR_FILTER_X2,
+                                 IIR_FILTER_X4, IIR_FILTER_X8, IIR_FILTER_X16))
+
+"""overscan values for temperature, pressure, and humidity"""
+OVERSCAN_DISABLE = const(0x00)
+OVERSCAN_X1 = const(0x01)
+OVERSCAN_X2 = const(0x02)
+OVERSCAN_X4 = const(0x03)
+OVERSCAN_X8 = const(0x04)
+OVERSCAN_X16 = const(0x05)
+
+_BMP280_OVERSCANS = {OVERSCAN_DISABLE:0, OVERSCAN_X1:1, OVERSCAN_X2:2,
+                     OVERSCAN_X4:4, OVERSCAN_X8:8, OVERSCAN_X16:16}
+
+"""mode values"""
+MODE_SLEEP = const(0x00)
+MODE_FORCE = const(0x01)
+MODE_NORMAL = const(0x03)
+
+_BMP280_MODES = frozenset((MODE_SLEEP, MODE_FORCE, MODE_NORMAL))
+"""
+standby timeconstant values
+TC_X[_Y] where X=milliseconds and Y=tenths of a millisecond
+"""
+STANDBY_TC_0_5 = const(0x00)    #0.5ms
+STANDBY_TC_10 = const(0x06)     #10ms
+STANDBY_TC_20 = const(0x07)     #20ms
+STANDBY_TC_62_5 = const(0x01)   #62.5ms
+STANDBY_TC_125 = const(0x02)    #125ms
+STANDBY_TC_250 = const(0x03)    #250ms
+STANDBY_TC_500 = const(0x04)    #500ms
+STANDBY_TC_1000 = const(0x05)   #1000ms
+
+_BMP280_STANDBY_TCS = frozenset((STANDBY_TC_0_5, STANDBY_TC_10, STANDBY_TC_20,
+                                 STANDBY_TC_62_5, STANDBY_TC_125, STANDBY_TC_250,
+                                 STANDBY_TC_500, STANDBY_TC_1000))
+
 class Adafruit_BMP280: # pylint: disable=invalid-name
     """Base BMP280 object. Use `Adafruit_BMP280_I2C` or `Adafruit_BMP280_SPI` instead of this. This
        checks the BMP280 was found, reads the coefficients and enables the sensor for continuous
@@ -72,56 +108,221 @@ def __init__(self):
         chip_id = self._read_byte(_REGISTER_CHIPID)
         if _CHIP_ID != chip_id:
             raise RuntimeError('Failed to find BMP280! Chip ID 0x%x' % chip_id)
+        #Set some reasonable defaults.
+        self._iir_filter = IIR_FILTER_DISABLE
+        self._overscan_temperature = OVERSCAN_X2
+        self._overscan_pressure = OVERSCAN_X16
+        self._t_standby = STANDBY_TC_0_5
+        self._mode = MODE_SLEEP
+        self._reset()
         self._read_coefficients()
+        self._write_ctrl_meas()
+        self._write_config()
         self.sea_level_pressure = 1013.25
         """Pressure in hectoPascals at sea level. Used to calibrate `altitude`."""
+        self._t_fine = None
 
-    def _read(self):
-        """Returns a tuple for temperature and pressure."""
-        # perform one measurement in high res, forced mode
-        self._write_register_byte(_REGISTER_CONTROL, 0xFE)
-
-        # Wait for conversion to complete
-        while self._read_byte(_REGISTER_STATUS) & 0x08:
-            time.sleep(0.002)
-        # lowest 4 bits get dropped
-        UT = self._read24(_REGISTER_TEMPDATA) / 16
+    def _read_temperature(self):
+        # perform one measurement
+        if self.mode != MODE_NORMAL:
+            self.mode = MODE_FORCE
+            # Wait for conversion to complete
+            while self._get_status() & 0x08:
+                sleep(0.002)
+        raw_temperature = self._read24(_REGISTER_TEMPDATA) / 16 # lowest 4 bits get dropped
         #print("raw temp: ", UT)
+        var1 = (raw_temperature / 16384.0 - self._temp_calib[0] / 1024.0) * self._temp_calib[1]
+        #print(var1)
+        var2 = ((raw_temperature / 131072.0 - self._temp_calib[0] / 8192.0) * (
+            raw_temperature / 131072.0 - self._temp_calib[0] / 8192.0)) * self._temp_calib[2]
+        #print(var2)
 
-        var1 = (UT / 16384.0 - self._temp_calib[0] / 1024.0) * self._temp_calib[1]
-        var2 = ((UT / 131072.0 - self._temp_calib[0] / 8192.0) * (
-            UT / 131072.0 - self._temp_calib[0] / 8192.0)) * self._temp_calib[2]
+        self._t_fine = int(var1 + var2)
         #print("t_fine: ", self.t_fine)
-        t_fine = int(var1 + var2)
-        temperature = t_fine / 5120.0
 
-        adc = self._read24(_REGISTER_PRESSUREDATA) / 16
-        var1 = float(t_fine) / 2.0 - 64000.0
-        var2 = var1 * var1 * self._pressure_calib[5] / 32768.0
-        var2 = var2 + var1 * self._pressure_calib[4] * 2.0
-        var2 = var2 / 4.0 + self._pressure_calib[3] * 65536.0
-        var1 = (self._pressure_calib[2] * var1 * var1 / 524288.0 +
-                self._pressure_calib[1] * var1) / 524288.0
-        var1 = (1.0 + var1 / 32768.0) * self._pressure_calib[0]
-        if var1 == 0:
-            return 0
-        p = 1048576.0 - adc
-        p = ((p - var2 / 4096.0) * 6250.0) / var1
-        var1 = self._pressure_calib[8] * p * p / 2147483648.0
-        var2 = p * self._pressure_calib[7] / 32768.0
-        p = p + (var1 + var2 + self._pressure_calib[6]) / 16.0
-        pressure = p / 100
-        return (temperature, pressure)
+    def _reset(self):
+        """Soft reset the sensor"""
+        self._write_register_byte(_REGISTER_SOFTRESET, 0xB6)
+        sleep(0.004)  #Datasheet says 2ms.  Using 4ms just to be safe
+
+    def _write_ctrl_meas(self):
+        """
+        Write the values to the ctrl_meas register in the device
+        ctrl_meas sets the pressure and temperature data acquistion options
+        """
+        self._write_register_byte(_REGISTER_CTRL_MEAS, self._ctrl_meas)
+
+    def _get_status(self):
+        """Get the value from the status register in the device """
+        return self._read_byte(_REGISTER_STATUS)
+
+    def _read_config(self):
+        """Read the value from the config register in the device """
+        return self._read_byte(_REGISTER_CONFIG)
+
+    def _write_config(self):
+        """Write the value to the config register in the device """
+        normal_flag = False
+        if self._mode == MODE_NORMAL:
+            #Writes to the config register may be ignored while in Normal mode
+            normal_flag = True
+            self.mode = MODE_SLEEP #So we switch to Sleep mode first
+        self._write_register_byte(_REGISTER_CONFIG, self._config)
+        if normal_flag:
+            self.mode = MODE_NORMAL
+
+    @property
+    def mode(self):
+        """
+        Operation mode
+        Allowed values are set in the MODE enum class
+        """
+        return self._mode
+
+    @mode.setter
+    def mode(self, value):
+        if not value in _BMP280_MODES:
+            raise ValueError('Mode \'%s\' not supported' % (value))
+        self._mode = value
+        self._write_ctrl_meas()
+
+    @property
+    def standby_period(self):
+        """
+        Control the inactive period when in Normal mode
+        Allowed standby periods are set the STANDBY enum class
+        """
+        return self._t_standby
+
+    @standby_period.setter
+    def standby_period(self, value):
+        if not value in _BMP280_STANDBY_TCS:
+            raise ValueError('Standby Period \'%s\' not supported' % (value))
+        if self._t_standby == value:
+            return
+        self._t_standby = value
+        self._write_config()
+
+    @property
+    def overscan_temperature(self):
+        """
+        Temperature Oversampling
+        Allowed values are set in the OVERSCAN enum class
+        """
+        return self._overscan_temperature
+
+    @overscan_temperature.setter
+    def overscan_temperature(self, value):
+        if not value in _BMP280_OVERSCANS:
+            raise ValueError('Overscan value \'%s\' not supported' % (value))
+        self._overscan_temperature = value
+        self._write_ctrl_meas()
+
+    @property
+    def overscan_pressure(self):
+        """
+        Pressure Oversampling
+        Allowed values are set in the OVERSCAN enum class
+        """
+        return self._overscan_pressure
+
+    @overscan_pressure.setter
+    def overscan_pressure(self, value):
+        if not value in _BMP280_OVERSCANS:
+            raise ValueError('Overscan value \'%s\' not supported' % (value))
+        self._overscan_pressure = value
+        self._write_ctrl_meas()
+
+    @property
+    def iir_filter(self):
+        """
+        Controls the time constant of the IIR filter
+        Allowed values are set in the IIR_FILTER enum class
+        """
+        return self._iir_filter
+
+    @iir_filter.setter
+    def iir_filter(self, value):
+        if not value in _BMP280_IIR_FILTERS:
+            raise ValueError('IIR Filter \'%s\' not supported' % (value))
+        self._iir_filter = value
+        self._write_config()
+
+    @property
+    def _config(self):
+        """Value to be written to the device's config register """
+        config = 0
+        if self.mode == MODE_NORMAL:
+            config += (self._t_standby << 5)
+        if self._iir_filter:
+            config += (self._iir_filter << 2)
+        return config
+
+    @property
+    def _ctrl_meas(self):
+        """Value to be written to the device's ctrl_meas register """
+        ctrl_meas = (self.overscan_temperature << 5)
+        ctrl_meas += (self.overscan_pressure << 2)
+        ctrl_meas += self.mode
+        return ctrl_meas
+
+    @property
+    def measurement_time_typical(self):
+        """Typical time in milliseconds required to complete a measurement in normal mode"""
+        meas_time_ms = 1
+        if self.overscan_temperature != OVERSCAN_DISABLE:
+            meas_time_ms += (2 * _BMP280_OVERSCANS.get(self.overscan_temperature))
+        if self.overscan_pressure != OVERSCAN_DISABLE:
+            meas_time_ms += (2 * _BMP280_OVERSCANS.get(self.overscan_pressure) + 0.5)
+        return meas_time_ms
+
+    @property
+    def measurement_time_max(self):
+        """Maximum time in milliseconds required to complete a measurement in normal mode"""
+        meas_time_ms = 1.25
+        if self.overscan_temperature != OVERSCAN_DISABLE:
+            meas_time_ms += (2.3 * _BMP280_OVERSCANS.get(self.overscan_temperature))
+        if self.overscan_pressure != OVERSCAN_DISABLE:
+            meas_time_ms += (2.3 * _BMP280_OVERSCANS.get(self.overscan_pressure) + 0.575)
+        return meas_time_ms
 
     @property
     def temperature(self):
         """The compensated temperature in degrees celsius."""
-        return self._read()[0]
+        self._read_temperature()
+        return self._t_fine / 5120.0
 
     @property
     def pressure(self):
-        """The compensated pressure in hectoPascals."""
-        return self._read()[1]
+        """
+        The compensated pressure in hectoPascals.
+        returns None if pressure measurement is disabled
+        """
+        self._read_temperature()
+
+        # Algorithm from the BMP280 driver
+        # https://github.com/BoschSensortec/BMP280_driver/blob/master/bmp280.c
+        adc = self._read24(_REGISTER_PRESSUREDATA) / 16  # lowest 4 bits get dropped
+        var1 = float(self._t_fine) / 2.0 - 64000.0
+        var2 = var1 * var1 * self._pressure_calib[5] / 32768.0
+        var2 = var2 + var1 * self._pressure_calib[4] * 2.0
+        var2 = var2 / 4.0 + self._pressure_calib[3] * 65536.0
+        var3 = self._pressure_calib[2] * var1 * var1 / 524288.0
+        var1 = (var3 + self._pressure_calib[1] * var1) / 524288.0
+        var1 = (1.0 + var1 / 32768.0) * self._pressure_calib[0]
+        if not var1:
+            return _BMP280_PRESSURE_MIN_HPA
+        pressure = 1048576.0 - adc
+        pressure = ((pressure - var2 / 4096.0) * 6250.0) / var1
+        var1 = self._pressure_calib[8] * pressure * pressure / 2147483648.0
+        var2 = pressure * self._pressure_calib[7] / 32768.0
+        pressure = pressure + (var1 + var2 + self._pressure_calib[6]) / 16.0
+        pressure /= 100
+        if pressure < _BMP280_PRESSURE_MIN_HPA:
+            return _BMP280_PRESSURE_MIN_HPA
+        if pressure > _BMP280_PRESSURE_MAX_HPA:
+            return _BMP280_PRESSURE_MAX_HPA
+        return pressure
 
     @property
     def altitude(self):

examples/bmp280_normal_mode.py

@@ -0,0 +1,35 @@
+"""
+Example showing how the BMP280 library can be used to set the various
+parameters supported by the sensor.
+Refer to the BMP280 datasheet to understand what these parameters do
+"""
+import time
+
+import board
+import busio
+import adafruit_bmp280
+
+# Create library object using our Bus I2C port
+i2c = busio.I2C(board.SCL, board.SDA)
+bmp280 = adafruit_bmp280.Adafruit_BMP280_I2C(i2c)
+
+# OR create library object using our Bus SPI port
+#spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
+#bmp_cs = digitalio.DigitalInOut(board.D10)
+#bmp280 = adafruit_bmp280.Adafruit_BMP280_SPI(spi, bmp_cs)
+
+# change this to match the location's pressure (hPa) at sea level
+bmp280.sea_level_pressure = 1013.25
+bmp280.mode = adafruit_bmp280.MODE_NORMAL
+bmp280.standby_period = adafruit_bmp280.STANDBY_TC_500
+bmp280.iir_filter = adafruit_bmp280.IIR_FILTER_X16
+bmp280.overscan_pressure = adafruit_bmp280.OVERSCAN_X16
+bmp280.overscan_temperature = adafruit_bmp280.OVERSCAN_X2
+#The sensor will need a moment to gather inital readings
+time.sleep(1)
+
+while True:
+    print("\nTemperature: %0.1f C" % bmp280.temperature)
+    print("Pressure: %0.1f hPa" % bmp280.pressure)
+    print("Altitude = %0.2f meters" % bmp280.altitude)
+    time.sleep(2)