#!/usr/bin/python
#--------------------------------------
# ___ ___ _ ____
# / _ \/ _ \(_) __/__ __ __
# / , _/ ___/ /\ \/ _ \/ // /
# /_/|_/_/ /_/___/ .__/\_, /
#
/_/ /___/
#
#
bmp180.py
# Read data from a digital pressure sensor.
#
# Author : Matt Hawkins
# Date : 17/02/2017
#
# http://www.raspberrypi-spy.co.uk/
#
#--------------------------------------
##import smbus
import board
import busio
import time
from ctypes import c_short
DEVICE = 0x77 # Default device I2C address
##bus = smbus.SMBus(0) # 0 indicates /dev/i2c-0
##bus = smbus.SMBus(1) # 1 indicates /dev/i2c-1
#i2c = busio.I2C(board.SCL, board.SDA)
i2c = busio.I2C(scl=board.SCL, sda=board.SDA)
def convertToString(data):
# Simple function to convert binary data into
# a string
return str((data[1] + (256 * data[0])) / 1.2)
def getShort(data, index):
# return two bytes from data as a signed 16-bit
value
return c_short((data[index] << 8) +
data[index + 1]).value
def getUshort(data, index):
# return two bytes from data as an unsigned 16-bit
value
return (data[index] << 8) + data[index + 1]
def readBmp180Id(addr=DEVICE):
# Chip ID Register Address
REG_ID = 0xD0
## (chip_id, chip_version) =
bus.read_i2c_block_data(addr, REG_ID, 2)
result = bytearray(2)
i2c.writeto_then_readfrom(addr, bytes([0xD0]),
result)
## return (chip_id, chip_version)
return (result[0], result[1])
def readBmp180(addr=DEVICE):
# Register Addresses
REG_CALIB = 0xAA
REG_MEAS = 0xF4
REG_MSB = 0xF6
REG_LSB = 0xF7
# Control Register Address
CRV_TEMP = 0x2E
CRV_PRES = 0x34
# Oversample setting
OVERSAMPLE = 3 # 0 - 3
# Read calibration data
# Read calibration data from EEPROM
## cal = bus.read_i2c_block_data(addr, REG_CALIB,
22)
cal = bytearray(22)
i2c.writeto_then_readfrom(addr, bytes([REG_CALIB]),
cal)
# Convert byte data to word values
AC1 = getShort(cal, 0)
AC2 = getShort(cal, 2)
AC3 = getShort(cal, 4)
AC4 = getUshort(cal, 6)
AC5 = getUshort(cal, 8)
AC6 = getUshort(cal, 10)
B1 = getShort(cal, 12)
B2 = getShort(cal, 14)
MB = getShort(cal, 16)
MC = getShort(cal, 18)
MD = getShort(cal, 20)
# Read temperature
## bus.write_byte_data(addr, REG_MEAS, CRV_TEMP)
i2c.writeto(addr, bytes([REG_MEAS, CRV_TEMP]),
stop=True)
time.sleep(0.005)
## (msb, lsb) = bus.read_i2c_block_data(addr,
REG_MSB, 2)
temperature = bytearray(2)
i2c.writeto_then_readfrom(addr, bytes([REG_MSB]),
temperature)
msb = temperature[0]
lsb = temperature[1]
UT = (msb << 8) + lsb
# Read pressure
## bus.write_byte_data(addr, REG_MEAS, CRV_PRES +
(OVERSAMPLE << 6))
i2c.writeto(addr, bytes([REG_MEAS, CRV_PRES +
(OVERSAMPLE << 6)]), stop=True)
time.sleep(0.04)
## (msb, lsb, xsb) = bus.read_i2c_block_data(addr,
REG_MSB, 3)
pressure = bytearray(3)
i2c.writeto_then_readfrom(addr, bytes([REG_MSB]),
pressure)
msb = pressure[0]
lsb = pressure[1]
xsb = pressure[2]
UP = ((msb << 16) + (lsb << 8) + xsb)
>> (8 - OVERSAMPLE)
# Refine temperature
X1 = ((UT - AC6) * AC5) >> 15
X2 = (MC << 11) / (X1 + MD)
B5 = X1 + X2
temperature = int(B5 + 8) >> 4
# Refine pressure
B6 = B5 - 4000
B62 = int(B6 * B6) >> 12
X1 = (B2 * B62) >> 11
X2 = int(AC2 * B6) >> 11
X3 = X1 + X2
B3 = (((AC1 * 4 + X3) << OVERSAMPLE) +
2) >> 2
X1 = int(AC3 * B6) >> 13
X2 = (B1 * B62) >> 16
X3 = ((X1 + X2) + 2) >> 2
B4 = (AC4 * (X3 + 32768)) >> 15
B7 = (UP - B3) * (50000 >> OVERSAMPLE)
P = (B7 * 2) / B4
X1 = (int(P) >> 8) * (int(P) >> 8)
X1 = (X1 * 3038) >> 16
X2 = int(-7357 * P) >> 16
pressure = int(P + ((X1 + X2 + 3791) >> 4))
return (temperature/10.0,pressure/100.0)
def main():
(chip_id, chip_version) = readBmp180Id()
print("Chip ID :
{0}".format(chip_id))
print("Version :
{0}".format(chip_version))
print
try:
print ("Press CTRL+C to exit")
while True:
(temperature,pressure)=readBmp180()
print("Temperature : {0}
C".format(temperature))
print("Pressure : {0}
mbar".format(pressure))
time.sleep(1)
except KeyboardInterrupt:
i2c.deinit()
if __name__=="__main__":
main()
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