Wiring and Test

You can easily wire this breakout to any microcontroller, we'll be using an Arduino. For another kind of microcontroller, as long as you have 4 available pins it is possible to 'bit-bang SPI'. Check out the library, then port the code.
Since this is a SPI sensor, we can use hardware or 'software' SPI. To make wiring identical on all Arduinos, we'll begin with 'software' SPI. The following pins should be used:
  • Connect Vin to the power supply, 3V or 5V is fine. Use the same voltage that the microcontroller logic is based off of. For most Arduinos, that is 5V
  • Connect GND to common power/data ground
  • Connect the SCK pin to Digital #13 but any pin can be used later
  • Connect the SDO pin to Digital #12 but any pin can be used later
  • Connect the SDI pin to Digital #11 but any pin can be used later
  • Connect the CS pin Digital #10 but any pin can be used later
Later on, once we get it working, we can adjust the library to use hardware SPI if you desire, or change the pins to other

Download Adafruit_BMP183 library


To begin reading sensor data, you will need to download Adafruit_BMP183 from our github repository. You can do that by visiting the github repo and manually downloading or, easier, just click this button to download the zip
Rename the uncompressed folder Adafruit_BMP183 and check that the Adafruit_BMP183 folder contains Adafruit_BMP183.cpp and Adafruit_BMP183.h

Place the Adafruit_BMP183 library folder your arduinosketchfolder/libraries/ folder.
You may need to create the libraries subfolder if its your first library. Restart the IDE.

We also have a great tutorial on Arduino library installation at:
http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use

Load Demo

Open up File->Examples->Adafruit_BMP183->BMP183test and upload to your Arduino wired up to the sensor
Once uploaded to your Arduino, open up the serial console at 9600 baud speed to see data being printed out

Temperature is calculated in degrees C, you can convert this to F by using the classic F = C * 9/5 + 32 equation.

Pressure is returned in the SI units of Pascals. 100 Pascals = 1 hPa = 1 millibar. Often times barometric pressure is reported in millibar or inches-mercury. For future reference 1 pascal =0.000295333727 inches of mercury, or 1 inch Hg = 3386.39 Pascal. So if you take the pascal value of say 100734 and divide by 3389.39 you'll get 29.72 inches-Hg.

You can also calculate Altitude. However, you can only really do a good accurate job of calculating altitude if you know the hPa pressure at sea level for your location and day! The sensor is quite precise but if you do not have the data updated for the current day then it can be difficult to get more accurate than 10 meters.

Library Reference

You can start out by creating a BMP183 object with either software SPI (where all four pins can be any I/O) using
Download: file
Adafruit_BMP183 bmp = Adafruit_BMP183(BMP183_CLK, BMP183_SDO, BMP183_SDI, BMP183_CS);
Or you can use hardware SPI. With hardware SPI you must use the hardware SPI pins for your Arduino - and each arduino type has different pins! Check the SPI reference to see what pins to use.
In this case, you can use any CS pin, but the other three pins are fixed
Download: file
Adafruit_BMP183 bmp = Adafruit_BMP183(BMP183_CS);
Once started, you can initialize the sensor with
Download: file
bmp.begin()
begin() will return True if the sensor was found, and False if not. If you get a False value back, check your wiring!
Reading temperature and pressure is easy, just call:
Download: file
bmp.getTemperature()
bmp.getPressure()
Temperature is always a floating point, in Centigrade. Pressure is a 32 bit integer with the pressure in Pascals. You may need to convert to a different value to match it with your weather report
It's also possible to turn the BMP183 into an altimeter. If you know the pressure at sea level, the library can calculate the current barometric pressure into altitude

Download: file
bmp.getAltitude(seaLevelPressure)
However, you can only really do a good accurate job of calculating altitude if you know the hPa pressure at sea level for your location and day! The sensor is quite precise but if you do not have the data updated for the current day then it can be difficult to get more accurate than 10 meters.

Pass in the current sea level pressure in hPa - so the value will be somewhere around ~1000. You can also test with the generic 1013.25 value.
This guide was first published on Jun 04, 2014. It was last updated on Jun 04, 2014. This page (Wiring and Test) was last updated on Jul 16, 2019.