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BMP180.py
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#!/usr/bin/python3
#-*- coding:utf-8 -*-
import time
import smbus
# Operating Modes
BMP180_ULTRALOWPOWER = 0
BMP180_STANDARD = 1
BMP180_HIGHRES = 2
BMP180_ULTRAHIGHRES = 3
# BMP085 Registers
BMP180_CAL_REGS_START = 0xAA
BMP180_CAL_REGS_COUNT = 11
BMP180_CONTROL_ADDR = 0xF4
BMP180_RAWDATA_ADDR = 0xF6
# Commands
BMP180_READ_TEMPCMD = 0x2E
BMP180_READ_PRESSURECMD = 0x34
#便于对应spec，留出ac[0] & b[0] 不用
BMP180_CAL_DEF = -32767
bmp180_ac = [BMP180_CAL_DEF, 8153,-1069,-14370,33272,26213,13876] # AC1-AC6
bmp180_b = [BMP180_CAL_DEF, 6515,37, BMP180_CAL_DEF,BMP180_CAL_DEF,BMP180_CAL_DEF,BMP180_CAL_DEF,BMP180_CAL_DEF] # B1-B7
bmp180_x = [BMP180_CAL_DEF, BMP180_CAL_DEF,BMP180_CAL_DEF,BMP180_CAL_DEF] # X1-X3
bmp180_mb = -32768
bmp180_mc = -11786
bmp180_md = 2081
class BMP180(object):
"""docstring for BMP180"""
def __init__(self, i2c_adddr=0x77):
self.addr = i2c_adddr
self.bus = smbus.SMBus(1)
self._load_calibration()
def _read(self, cmd):
return self.bus.read_byte_data(self.addr, cmd)
def _write(self, cmd, val):
return self.bus.write_byte_data(self.addr, cmd, val)
def _load_calibration(self):
cal=[]
for i in range(0,BMP180_CAL_REGS_COUNT):
MSB = self._read(BMP180_CAL_REGS_START+i*2)
LSB = self._read(BMP180_CAL_REGS_START+i*2+1)
value = (MSB << 8) + LSB
if i in {0, 1, 2, 6, 7, 8, 9, 10}:# signed short
if value > 32767:value -= 65536
cal.append(value)
# fill the regs
for i in range(1,6):
bmp180_ac[i]=cal[i-1]
bmp180_b[1] = cal[6]
bmp180_b[2] = cal[7]
bmp180_mb = cal[8]
bmp180_mc = cal[9]
bmp180_md = cal[10]
#print(bmp180_ac, bmp180_b)
def get_temperature(self):
# for temperature
self._write(BMP180_CONTROL_ADDR, BMP180_READ_TEMPCMD)
time.sleep(0.005) # Wait 4.5(in fact is 5)ms
MSB = self._read(BMP180_RAWDATA_ADDR)
LSB = self._read(BMP180_RAWDATA_ADDR+1)
ut = (MSB << 8) + LSB
# Calculate it
bmp180_x[1] = ((ut-bmp180_ac[6])*bmp180_ac[5])>>15
bmp180_x[2] = (bmp180_mc <<11) / (bmp180_x[1]+bmp180_md)
bmp180_b[5] = bmp180_x[1] + bmp180_x[2]
self.temperature = float( ((bmp180_b[5]+8) >>4)/10.0 )
#print("IN temp: ut=%d, x1=%d, x2=%d, b5=%d, t=%d " %( ut, bmp180_x[1], bmp180_x[2], bmp180_b[5], t))
return self.temperature
def get_pressure(self, oss=BMP180_STANDARD):
if bmp180_b[5]==BMP180_CAL_DEF: #没有调用温度计算过
self.get_temperature()
# for pressure
self._write(BMP180_CONTROL_ADDR, BMP180_READ_PRESSURECMD + (oss << 6))
if oss == BMP180_ULTRALOWPOWER:
time.sleep(0.005)
elif oss == BMP180_STANDARD:
time.sleep(0.008)
elif oss == BMP180_HIGHRES:
time.sleep(0.014)
elif oss == BMP180_ULTRAHIGHRES:
time.sleep(0.026)
else:
print("BMP180: error input for pressure oss")
MSB = self._read(BMP180_RAWDATA_ADDR)
LSB = self._read(BMP180_RAWDATA_ADDR+1)
XLSB = self._read(BMP180_RAWDATA_ADDR+2)
up = ((MSB << 16) + (LSB << 8) + XLSB) >> (8 - oss)
# Calculate it
bmp180_b[6] = bmp180_b[5]-4000
temp = bmp180_b[6]*bmp180_b[6]>>12
bmp180_x[1] = (bmp180_b[2] * temp ) >> 11
bmp180_x[2] = (bmp180_ac[2] * bmp180_b[6]) >> 11
bmp180_x[3] = bmp180_x[1]+bmp180_x[2]
bmp180_b[3] = (((bmp180_ac[1]*4 + bmp180_x[3])<<oss) +2) /4
bmp180_x[1] = (bmp180_ac[3] * bmp180_b[6]) >> 13
bmp180_x[2] = (bmp180_b[1] * temp ) >> 16
bmp180_x[3] = (bmp180_x[1]+bmp180_x[2] +2 )>>2
bmp180_b[4] = (bmp180_ac[4]* (bmp180_x[3]+32768)) >> 15
bmp180_b[7] = (up - bmp180_b[3]) * (50000>>oss)
if bmp180_b[7] < 0x80000000:
p = bmp180_b[7]*2/bmp180_b[4]
else:
p = bmp180_b[7]/bmp180_b[4]*2
bmp180_x[1] = (p>>8) * (p>>8)
bmp180_x[1] = (bmp180_x[1]*3038) >>16
bmp180_x[2] = (-7357*p) >>16
self.pressure = p + ((bmp180_x[1] + bmp180_x[2] + 3791) >> 4)
return self.pressure
def get_altitude(self, sealevel_pa=101325.0):
self.get_pressure()#重新计算气压
self.altitude = 44330.0 * (1.0 - pow(self.pressure / sealevel_pa, (1.0/5.255)))
return self.altitude
def cal_sealevel_pressure(self, altitude=0.0):
p0 = self.pressure / pow(1.0 - altitude/44330.0, 5.255)
return p0
def __exit__(self):
self.bus.close()