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bme280.py
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bme280.py
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from microbit import *
BME280_I2C_ADDR = 0x76
class BME280():
def __init__(self):
"""基本描述
BME280温度, 湿度, 气压传感器
Returns:
temperature 摄氏温度 humidity 湿度 0-100 pressure 气压 hPa altitude 海拔高度 M 根据气压换算
"""
self._T1 = self.__g2r(0x88)
self._T2 = self.__short(self.__g2r(0x8A))
self._T3 = self.__short(self.__g2r(0x8C))
self._P1 = self.__g2r(0x8E)
self._P2 = self.__short(self.__g2r(0x90))
self._P3 = self.__short(self.__g2r(0x92))
self._P4 = self.__short(self.__g2r(0x94))
self._P5 = self.__short(self.__g2r(0x96))
self._P6 = self.__short(self.__g2r(0x98))
self._P7 = self.__short(self.__g2r(0x9A))
self._P8 = self.__short(self.__g2r(0x9C))
self._P9 = self.__short(self.__g2r(0x9E))
self._H1 = self.__gr(0xA1)
self._H2 = self.__short(self.__g2r(0xE1))
self._H3 = self.__gr(0xE3)
a = self.__gr(0xE5)
self._H4 = (self.__gr(0xE4) << 4) + (a % 16)
self._H5 = (self.__gr(0xE6) << 4) + (a >> 4)
self._H6 = self.__gr(0xE7)
if self._H6 > 127:
self._H6 -= 256
self.__sr(0xF2, 0x04)
self.__sr(0xF4, 0x2F)
self.__sr(0xF5, 0x0C)
self.__T = 0
self.__P = 0
self._H = 0
def __short(self, dat):
if dat > 32767:
return dat - 65536
else:
return dat
# set reg
def __sr(self, reg, dat):
i2c.write(BME280_I2C_ADDR, bytearray([reg, dat]))
# __get reg
def __gr(self, reg):
i2c.write(BME280_I2C_ADDR, bytearray([reg]))
t = i2c.read(BME280_I2C_ADDR, 1)
return t[0]
# __get two reg
def __g2r(self, reg):
i2c.write(BME280_I2C_ADDR, bytearray([reg]))
t = i2c.read(BME280_I2C_ADDR, 2)
return t[0] + t[1] * 256
def __get(self):
adc_T = (self.__gr(0xFA) << 12) + (self.__gr(0xFB) << 4) + \
(self.__gr(0xFC) >> 4)
var1 = (((adc_T >> 3) - (self._T1 << 1)) * self._T2) >> 11
var2 = (((((adc_T >> 4) - self._T1) * ((adc_T >> 4) - self._T1)) >> 12)
* self._T3) >> 14
t = var1 + var2
self.__T = ((t * 5 + 128) >> 8) / 100
var1 = (t >> 1) - 64000
var2 = (((var1 >> 2) * (var1 >> 2)) >> 11) * self._P6
var2 = var2 + ((var1 * self._P5) << 1)
var2 = (var2 >> 2) + (self._P4 << 16)
var1 = (((self._P3 * ((var1 >> 2) * (var1 >> 2)) >> 13) >> 3) +
(((self._P2) * var1) >> 1)) >> 18
var1 = ((32768 + var1) * self._P1) >> 15
if var1 == 0:
return # avoid exception caused by division by zero
adc_P = (self.__gr(0xF7) << 12) + (self.__gr(0xF8) << 4) + \
(self.__gr(0xF9) >> 4)
p = ((1048576 - adc_P) - (var2 >> 12)) * 3125
if p < 0x80000000:
p = (p << 1) // var1
else:
p = (p // var1) * 2
var1 = (self._P9 * (((p >> 3) * (p >> 3)) >> 13)) >> 12
var2 = ((p >> 2) * self._P8) >> 13
self.__P = p + ((var1 + var2 + self._P7) >> 4)
adc_H = (self.__gr(0xFD) << 8) + self.__gr(0xFE)
var1 = t - 76800
var2 = (((adc_H << 14) - (self._H4 << 20) -
(self._H5 * var1)) + 16384) >> 15
var1 = var2 * (((((((var1 * self._H6) >> 10) * (
((var1 * self._H3) >> 11) + 32768)) >> 10) + 2097152) *
self._H2 + 8192) >> 14)
var2 = var1 - (((((var1 >> 15) * (var1 >> 15)) >> 7) * self._H1) >> 4)
if var2 < 0:
var2 = 0
if var2 > 419430400:
var2 = 419430400
self._H = (var2 >> 12) / 1024
return [self.__T, self.__P, self._H]
# __get Temperature in Celsius ℃
def get_temperature(self):
"""
读取摄氏温度 C
"""
self.__get()
return self.__T
# __get Humidity in %RH
def get_humidity(self):
"""
读取湿度 %
"""
self.__get()
return self._H
# __get Pressure in Pa
def get_pressure(self):
"""
读取气压 pa
"""
self.__get()
return self.__P
# Calculating absolute altitude
def get_altitude(self):
"""
读取海拔高度 M
"""
self.__get()
return 44330 * (1 - (self.__P / 101325) ** (1 / 5.255))
# normal mode
def set_power_on(self):
"""
模块开始工作，实时监测环境变量
"""
self.__sr(0xF4, 0x2F)
# sleep mode
def set_power_off(self):
"""
模块休眠，保留最后一次检测的环境值，不会刷新
"""
self.__sr(0xF4, 0)
if __name__ == '__main__':
bme = BME280()
while True:
print("BME280_temperature_C:", bme.get_temperature(), "C")
print("BME280_humidity:", bme.get_humidity(), "%")
print("BME280_pressure:", bme.get_pressure(), "hPa")
print("BME280_altitude:", bme.get_altitude(), "M")
print("")
sleep(500)