140 line
3.7 KiB
Python
140 line
3.7 KiB
Python
import time
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from . import logger, background_task
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try:
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import smbus
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except ImportError:
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logger.warning("Could not import smbus. DEBUG set to True.")
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DEBUG = True
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else:
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from . import DEBUG
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class bmp_180(background_task):
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RUN_SLEEP_TIME = 0.5
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SMBUS_DELAY = 0.5
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MIN_REFRESH_RATE = RUN_SLEEP_TIME + 3 * SMBUS_DELAY
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KEY_TEMPERATURE = 'temperature'
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KEY_PRESSURE = 'pressure'
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KEY_TIME = 'time'
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def __init__(self, data_callback=None):
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self.__data_callback__ = data_callback
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# Initialise background_task
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background_task.__init__(self)
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def __run__(self):
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data = self.__bmp_data_transmission__()
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if data is not None:
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logger.debug('BMP-Communication: Successfully: %s', repr(data))
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if self.__data_callback__ is not None:
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self.__data_callback__(**data)
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def __bmp_data_transmission__(self):
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if not DEBUG:
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rv = {}
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# Get I2C bus
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bus = smbus.SMBus(1)
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# BMP180 address, 0x77(119)
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# Read data back from 0xAA(170), 22 bytes
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data = bus.read_i2c_block_data(0x77, 0xAA, 22)
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# Convert the data
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AC1 = data[0] * 256 + data[1]
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if AC1 > 32767 :
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AC1 -= 65535
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AC2 = data[2] * 256 + data[3]
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if AC2 > 32767 :
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AC2 -= 65535
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AC3 = data[4] * 256 + data[5]
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if AC3 > 32767 :
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AC3 -= 65535
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AC4 = data[6] * 256 + data[7]
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AC5 = data[8] * 256 + data[9]
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AC6 = data[10] * 256 + data[11]
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B1 = data[12] * 256 + data[13]
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if B1 > 32767 :
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B1 -= 65535
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B2 = data[14] * 256 + data[15]
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if B2 > 32767 :
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B2 -= 65535
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MB = data[16] * 256 + data[17]
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if MB > 32767 :
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MB -= 65535
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MC = data[18] * 256 + data[19]
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if MC > 32767 :
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MC -= 65535
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MD = data[20] * 256 + data[21]
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if MD > 32767 :
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MD -= 65535
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time.sleep(self.SMBUS_DELAY)
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# BMP180 address, 0x77(119)
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# Select measurement control register, 0xF4(244)
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# 0x2E(46) Enable temperature measurement
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bus.write_byte_data(0x77, 0xF4, 0x2E)
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time.sleep(self.SMBUS_DELAY)
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# BMP180 address, 0x77(119)
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# Read data back from 0xF6(246), 2 bytes
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# temp MSB, temp LSB
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data = bus.read_i2c_block_data(0x77, 0xF6, 2)
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# Convert the data
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temp = data[0] * 256 + data[1]
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# BMP180 address, 0x77(119)
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# Select measurement control register, 0xF4(244)
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# 0x74(116) Enable pressure measurement, OSS = 1
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bus.write_byte_data(0x77, 0xF4, 0x74)
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time.sleep(self.SMBUS_DELAY)
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# BMP180 address, 0x77(119)
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# Read data back from 0xF6(246), 3 bytes
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# pres MSB1, pres MSB, pres LSB
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data = bus.read_i2c_block_data(0x77, 0xF6, 3)
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rv[self.KEY_TIME] = int(time.time())
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# Convert the data
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pres = ((data[0] * 65536) + (data[1] * 256) + data[2]) / 128
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# Callibration for Temperature
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X1 = (temp - AC6) * AC5 / 32768.0
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X2 = (MC * 2048.0) / (X1 + MD)
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B5 = X1 + X2
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rv[self.KEY_TEMPERATURE] = ((B5 + 8.0) / 16.0) / 10.0
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# Calibration for Pressure
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B6 = B5 - 4000
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X1 = (B2 * (B6 * B6 / 4096.0)) / 2048.0
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X2 = AC2 * B6 / 2048.0
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X3 = X1 + X2
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B3 = (((AC1 * 4 + X3) * 2) + 2) / 4.0
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X1 = AC3 * B6 / 8192.0
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X2 = (B1 * (B6 * B6 / 2048.0)) / 65536.0
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X3 = ((X1 + X2) + 2) / 4.0
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B4 = AC4 * (X3 + 32768) / 32768.0
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B7 = ((pres - B3) * (25000.0))
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pressure = 0.0
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if B7 < 2147483648:
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pressure = (B7 * 2) / B4
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else :
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pressure = (B7 / B4) * 2
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X1 = (pressure / 256.0) * (pressure / 256.0)
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X1 = (X1 * 3038.0) / 65536.0
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X2 = ((-7357) * pressure) / 65536.0
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rv[self.KEY_PRESSURE] = (pressure + (X1 + X2 + 3791) / 16.0) / 100
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return rv
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else:
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time.sleep(3 * self.SMBUS_DELAY)
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return {
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self.KEY_PRESSURE: 1717.,
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self.KEY_TEMPERATURE: 17.17,
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self.KEY_TIME: int(time.time())
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}
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