sudo apt-get update sudo apt-get install git build-essential python-dev python-smbus git clone https://github.com/adafruit/Adafruit_Python_BMP.git cd Adafruit_Python_BMP sudo python setup.py install
Once the library is installed it will be accessible to any Python script on your device. You can see a few example scripts included in the library source's examples folder. Try running the simpletest.py example which grabs a single reading from the BMP sensor and displays it by executing:
cd examples sudo python simpletest.py
After running the script you should see an output such as:
Temp = 20.20 *C
Pressure = 101667.00 Pa
Altitude = -28.27 m
Sealevel Pressure = 101665.00 Pa
Open the simpletest.py code in a text editor to see how to use the library to read the BMP sensor. First the library is imported with this command:
import Adafruit_BMP.BMP085 as BMP085
# Default constructor will pick a default I2C bus. # # For the Raspberry Pi this means you should hook up to the only exposed I2C bus # from the main GPIO header and the library will figure out the bus number based # on the Pi's revision. # # For the Beaglebone Black the library will assume bus 1 by default, which is # exposed with SCL = P9_19 and SDA = P9_20. sensor = BMP085.BMP085() # Optionally you can override the bus number: #sensor = BMP085.BMP085(busnum=2) # You can also optionally change the BMP085 mode to one of BMP085_ULTRALOWPOWER, # BMP085_STANDARD, BMP085_HIGHRES, or BMP085_ULTRAHIGHRES. See the BMP085 # datasheet for more details on the meanings of each mode (accuracy and power # consumption are primarily the differences). The default mode is STANDARD. #sensor = BMP085.BMP085(mode=BMP085.BMP085_ULTRAHIGHRES)
You can see from the comments there are a few ways to create the sensor instance. By default if you pass no parameters the library will try to find the right I2C bus for your device. For a Raspberry Pi the library will detect the revision number and use the appropriate bus (0 or 1). For a Beaglebone Black there are multiple I2C buses so the library defaults to bus 1, which is exposed with pin P9_19 as SCL clock and P9_20 as SDA data. You can explicitly set the bus number by passing it in the busnum parameter.
Note if you're using a BeagleBone Black with the Ubuntu operating system you might need to change busnum to 2 to use the P9_19 & P9_20 pin I2C connection. Just change the line to look like: sensor = BMP.BMP085(busnum=2)
The library will also choose by default to use the BMP sensor's standard operation mode. You can override this by passing a mode parameter with an explicit mode value--check the BMP datasheet for more information on its modes.
Once the BMP sensor instance is created, you can read its values by calling the read_temperature, read_pressure, read_altitude, and read_sealevel_pressure functions like below:
print 'Temp = {0:0.2f} *C'.format(sensor.read_temperature())
print 'Pressure = {0:0.2f} Pa'.format(sensor.read_pressure())
print 'Altitude = {0:0.2f} m'.format(sensor.read_altitude())
print 'Sealevel Pressure = {0:0.2f} Pa'.format(sensor.read_sealevel_pressure())
For another example of using the BMP library, check out the google_spreadsheet.py example. This code is similar to the DHT sensor Google Docs spreadsheet logging code, but is modified to use the BMP sensor and write the temperature, pressure, and altitude to a Google Docs spreadsheet. Check out the page on configuring Google Docs to see more details on how to create the spreadsheet and configure the username, password, and spreadsheet name.
