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April 24, 2020 05:57
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import smbus | |
import sys | |
import time | |
from ctypes import c_short | |
from ctypes import c_byte | |
from ctypes import c_ubyte | |
if len(sys.argv) == 2: | |
DEVICE = int(sys.argv[1],16) | |
else: | |
print('-1 | -1') | |
sys.exit(1) | |
bus = smbus.SMBus(1) # Rev 2 Pi, Pi 2 & Pi 3 uses bus 1 | |
# Rev 1 Pi uses bus 0 | |
def getShort(data, index): | |
# return two bytes from data as a signed 16-bit value | |
return c_short((data[index+1] << 8) + data[index]).value | |
def getUShort(data, index): | |
# return two bytes from data as an unsigned 16-bit value | |
return (data[index+1] << 8) + data[index] | |
def getChar(data,index): | |
# return one byte from data as a signed char | |
result = data[index] | |
if result > 127: | |
result -= 256 | |
return result | |
def getUChar(data,index): | |
# return one byte from data as an unsigned char | |
result = data[index] & 0xFF | |
return result | |
def readBME280ID(addr=DEVICE): | |
# Chip ID Register Address | |
REG_ID = 0xD0 | |
(chip_id, chip_version) = bus.read_i2c_block_data(addr, REG_ID, 2) | |
return (chip_id, chip_version) | |
def readBME280All(addr=DEVICE): | |
# Register Addresses | |
REG_DATA = 0xF7 | |
REG_CONTROL = 0xF4 | |
REG_CONFIG = 0xF5 | |
REG_CONTROL_HUM = 0xF2 | |
REG_HUM_MSB = 0xFD | |
REG_HUM_LSB = 0xFE | |
# Oversample setting - page 27 | |
OVERSAMPLE_TEMP = 2 | |
OVERSAMPLE_PRES = 2 | |
MODE = 1 | |
# Oversample setting for humidity register - page 26 | |
OVERSAMPLE_HUM = 2 | |
bus.write_byte_data(addr, REG_CONTROL_HUM, OVERSAMPLE_HUM) | |
control = OVERSAMPLE_TEMP<<5 | OVERSAMPLE_PRES<<2 | MODE | |
bus.write_byte_data(addr, REG_CONTROL, control) | |
# Read blocks of calibration data from EEPROM | |
# See Page 22 data sheet | |
cal1 = bus.read_i2c_block_data(addr, 0x88, 24) | |
cal2 = bus.read_i2c_block_data(addr, 0xA1, 1) | |
cal3 = bus.read_i2c_block_data(addr, 0xE1, 7) | |
# Convert byte data to word values | |
dig_T1 = getUShort(cal1, 0) | |
dig_T2 = getShort(cal1, 2) | |
dig_T3 = getShort(cal1, 4) | |
dig_P1 = getUShort(cal1, 6) | |
dig_P2 = getShort(cal1, 8) | |
dig_P3 = getShort(cal1, 10) | |
dig_P4 = getShort(cal1, 12) | |
dig_P5 = getShort(cal1, 14) | |
dig_P6 = getShort(cal1, 16) | |
dig_P7 = getShort(cal1, 18) | |
dig_P8 = getShort(cal1, 20) | |
dig_P9 = getShort(cal1, 22) | |
dig_H1 = getUChar(cal2, 0) | |
dig_H2 = getShort(cal3, 0) | |
dig_H3 = getUChar(cal3, 2) | |
dig_H4 = getChar(cal3, 3) | |
dig_H4 = (dig_H4 << 24) >> 20 | |
dig_H4 = dig_H4 | (getChar(cal3, 4) & 0x0F) | |
dig_H5 = getChar(cal3, 5) | |
dig_H5 = (dig_H5 << 24) >> 20 | |
dig_H5 = dig_H5 | (getUChar(cal3, 4) >> 4 & 0x0F) | |
dig_H6 = getChar(cal3, 6) | |
# Wait in ms (Datasheet Appendix B: Measurement time and current calculation) | |
wait_time = 1.25 + (2.3 * OVERSAMPLE_TEMP) + ((2.3 * OVERSAMPLE_PRES) + 0.575) + ((2.3 * OVERSAMPLE_HUM)+0.575) | |
time.sleep(wait_time/1000) # Wait the required time | |
# Read temperature/pressure/humidity | |
data = bus.read_i2c_block_data(addr, REG_DATA, 8) | |
pres_raw = (data[0] << 12) | (data[1] << 4) | (data[2] >> 4) | |
temp_raw = (data[3] << 12) | (data[4] << 4) | (data[5] >> 4) | |
hum_raw = (data[6] << 8) | data[7] | |
#Refine temperature | |
var1 = ((((temp_raw>>3)-(dig_T1<<1)))*(dig_T2)) >> 11 | |
var2 = (((((temp_raw>>4) - (dig_T1)) * ((temp_raw>>4) - (dig_T1))) >> 12) * (dig_T3)) >> 14 | |
t_fine = var1+var2 | |
temperature = float(((t_fine * 5) + 128) >> 8); | |
# Refine pressure and adjust for temperature | |
var1 = t_fine / 2.0 - 64000.0 | |
var2 = var1 * var1 * dig_P6 / 32768.0 | |
var2 = var2 + var1 * dig_P5 * 2.0 | |
var2 = var2 / 4.0 + dig_P4 * 65536.0 | |
var1 = (dig_P3 * var1 * var1 / 524288.0 + dig_P2 * var1) / 524288.0 | |
var1 = (1.0 + var1 / 32768.0) * dig_P1 | |
if var1 == 0: | |
pressure=0 | |
else: | |
pressure = 1048576.0 - pres_raw | |
pressure = ((pressure - var2 / 4096.0) * 6250.0) / var1 | |
var1 = dig_P9 * pressure * pressure / 2147483648.0 | |
var2 = pressure * dig_P8 / 32768.0 | |
pressure = pressure + (var1 + var2 + dig_P7) / 16.0 | |
# Refine humidity | |
humidity = t_fine - 76800.0 | |
humidity = (hum_raw - (dig_H4 * 64.0 + dig_H5 / 16384.0 * humidity)) * (dig_H2 / 65536.0 * (1.0 + dig_H6 / 67108864.0 * humidity * (1.0 + dig_H3 / 67108864.0 * humidity))) | |
humidity = humidity * (1.0 - dig_H1 * humidity / 524288.0) | |
if humidity > 100: | |
humidity = 100 | |
elif humidity < 0: | |
humidity = 0 | |
return temperature/100.0,pressure/100.0,humidity | |
def main(): | |
try: | |
temperature,pressure,humidity = readBME280All() | |
print('{0:0.1f} | {1:0.1f}'.format(temperature, humidity)) | |
except: | |
print('-1 | -1') | |
if __name__=="__main__": | |
main() |
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