bme280.py
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Raspberry Pi上のPythonでI2Cを制御する為に、smbusモジュールを使用します。
smbusモジュールがインストールされていない場合、下記コマンドでインストールしてください。
pip install smbus
bme280.pyはパッケージとしてimportして使用しますが、テスト用に単体で温湿度・気圧データを取得できます。
#!/usr/bin/env python
# -*- coding:utf-8 -*-
"""
BM280 script.
=============
Temperature: -40 to +85 [degC]
Dumidity: 0 ot 100[%]
barometer: 300 to 1100[hPa]
"""
i2c_enable = False
try:
import smbus
i2c_enable = True
except:
i2c_enable = False
import random
import time
class BME280():
def __init__(self):
self.bus_number = 1
self.i2c_address = 0x76
self.i2c_enable = i2c_enable
if self.i2c_enable:
self.bus = smbus.SMBus(self.bus_number)
else:
self.bus = self.SMBus(self.bus_number)
return
self.digT = []
self.digP = []
self.digH = []
self.t_fine = 0.0
self.setup()
self.get_calib_param()
@property
def barometer(self):
result = float(f'{random.uniform(1020.0, 1040.0):.2f}')
if self.i2c_enable == False:
return result
# For I2C error at pushed power switch.
try:
pres_raw = self._read_bus_data('barometer')
except:
return result
pressure = 0.0
v1 = (self.t_fine / 2.0) - 64000.0
v2 = (((v1 / 4.0) * (v1 / 4.0)) / 2048) * self.digP[5]
v2 = v2 + ((v1 * self.digP[4]) * 2.0)
v2 = (v2 / 4.0) + (self.digP[3] * 65536.0)
v1 = (((self.digP[2] * (((v1 / 4.0) * (v1 / 4.0)) / 8192)) / 8) + ((self.digP[1] * v1) / 2.0)) / 262144
v1 = ((32768 + v1) * self.digP[0]) / 32768
if v1 == 0:
return 0
pressure = ((1048576 - pres_raw) - (v2 / 4096)) * 3125
if pressure < 0x80000000:
pressure = (pressure * 2.0) / v1
else:
pressure = (pressure / v1) * 2
v1 = (self.digP[8] * (((pressure / 8.0) * (pressure / 8.0)) / 8192.0)) / 4096
v2 = ((pressure / 4.0) * self.digP[7]) / 8192.0
pressure = pressure + ((v1 + v2 + self.digP[6]) / 16.0)
#print('pressure : %7.2f hPa' % (pressure/100))
result = float(f'{pressure/100:7.2f}')
return result
def get_calib_param(self):
if self.i2c_enable == False:
return
calib = []
for i in range (0x88,0x88+24):
calib.append(self.bus.read_byte_data(self.i2c_address,i))
calib.append(self.bus.read_byte_data(self.i2c_address,0xA1))
for i in range (0xE1,0xE1+7):
calib.append(self.bus.read_byte_data(self.i2c_address,i))
self.digT.append((calib[1] << 8) | calib[0])
self.digT.append((calib[3] << 8) | calib[2])
self.digT.append((calib[5] << 8) | calib[4])
self.digP.append((calib[7] << 8) | calib[6])
self.digP.append((calib[9] << 8) | calib[8])
self.digP.append((calib[11]<< 8) | calib[10])
self.digP.append((calib[13]<< 8) | calib[12])
self.digP.append((calib[15]<< 8) | calib[14])
self.digP.append((calib[17]<< 8) | calib[16])
self.digP.append((calib[19]<< 8) | calib[18])
self.digP.append((calib[21]<< 8) | calib[20])
self.digP.append((calib[23]<< 8) | calib[22])
self.digH.append( calib[24] )
self.digH.append((calib[26]<< 8) | calib[25])
self.digH.append( calib[27] )
self.digH.append((calib[28]<< 4) | (0x0F & calib[29]))
self.digH.append((calib[30]<< 4) | ((calib[29] >> 4) & 0x0F))
self.digH.append( calib[31] )
for i in range(1,2):
if self.digT[i] & 0x8000:
self.digT[i] = (-self.digT[i] ^ 0xFFFF) + 1
for i in range(1,8):
if self.digP[i] & 0x8000:
self.digP[i] = (-self.digP[i] ^ 0xFFFF) + 1
for i in range(0,6):
if self.digH[i] & 0x8000:
self.digH[i] = (-self.digH[i] ^ 0xFFFF) + 1
@property
def humidity(self):
result = float(f'{random.uniform(10.0, 60.0):.2f}')
if self.i2c_enable == False:
return result
# For I2C error at pushed power switch.
try:
hum_raw = self._read_bus_data('humidity')
except:
return result
var_h = self.t_fine - 76800.0
if var_h != 0:
var_h = (hum_raw - (self.digH[3] * 64.0 + self.digH[4]/16384.0 * var_h))\
* (self.digH[1] / 65536.0\
* (1.0 + self.digH[5] / 67108864.0 * var_h \
* (1.0 + self.digH[2] / 67108864.0 * var_h)))
else:
return 0
var_h = var_h * (1.0 - self.digH[0] * var_h / 524288.0)
if var_h > 100.0:
var_h = 100.0
elif var_h < 0.0:
var_h = 0.0
#print('hum : %6.2f ％' % (var_h))
result = float(f'{var_h:.2f}')
return result
def _read_bus_data(self, data_type):
"""
data_tpye: 'temperature' or 'hidumity' or 'barometer'
"""
data = []
for i in range (0xF7, 0xF7+8):
data.append(self.bus.read_byte_data(self.i2c_address,i))
if data_type == 'barometer':
return (data[0] << 12) | (data[1] << 4) | (data[2] >> 4)
elif data_type == 'humidity':
return (data[6] << 8) | data[7]
elif data_type == 'temperature':
return (data[3] << 12) | (data[4] << 4) | (data[5] >> 4)
else:
return [0]
def read_data(self):
t = self.temperature
h = self.humidity
p = self.barometer
return [t, h, p]
def setup(self, ):
osrs_t = 1 #Temperature oversampling x 1
osrs_p = 1 #Pressure oversampling x 1
osrs_h = 1 #Humidity oversampling x 1
mode = 3 #Normal mode
t_sb = 5 #Tstandby 1000ms
filter = 0 #Filter off
spi3w_en = 0 #3-wire SPI Disable
ctrl_meas_reg = (osrs_t << 5) | (osrs_p << 2) | mode
config_reg = (t_sb << 5) | (filter << 2) | spi3w_en
ctrl_hum_reg = osrs_h
self.write_reg(0xF2,ctrl_hum_reg)
self.write_reg(0xF4,ctrl_meas_reg)
self.write_reg(0xF5,config_reg)
# Dummy SMBus.
class SMBus():
def __init__(self, *args, **kwargs):
pass
@property
def temperature(self):
result = float(f'{random.uniform(20.0, 40.0):.2f}')
if self.i2c_enable == False:
return result
# For I2C error at pushed power switch.
try:
temp_raw = self._read_bus_data('temperature')
except:
return result
v1 = (temp_raw / 16384.0 - self.digT[0] / 1024.0) * self.digT[1]
v2 = (temp_raw / 131072.0 - self.digT[0] / 8192.0) * (temp_raw / 131072.0 - self.digT[0] / 8192.0) * self.digT[2]
self.t_fine = v1 + v2
temperature = self.t_fine / 5120.0
result = float(f'{temperature:.2f}')
return result
def write_reg(self, reg_address, data):
if self.i2c_enable == False:
return
try:
self.bus.write_byte_data(self.i2c_address, reg_address, data)
except:
self.i2c_enable = False
self.bus = self.SMBus(self.bus_number)
if __name__ == '__main__':
em = BME280()
while True:
print(em.read_data())
#print(em.barometer)
#print(em.humidity)
#print(em.temperature)
time.sleep(0.5)
bme280.py