The JeeLabs Pressure Plug is a small board containing the Bosch BMP085 barometric pressure and temperature sensor. This tiny sensor communicates directly over I2C. The sensor is exquisitely sensitive, and with some filtering can detect changes in atmospheric pressure as small as a 1 foot change in altitude. It easily detects the difference between holding it at floor level and holding it over at arm’s reach overhead.

The pinout of the pressure plug board is specifically setup to mate seamlessly with JeeNodes, but the 3.3V I2C device can also be used with any 3.3V microcontroller with I2C functionality. Some processing is required to arrive at properly adjusted readings, since the sensing element responds to both temperature and pressure is available by using the JeeLabs “BMP085” class in the Ports library.

The Pressure Plug also makes a fine (3.3V) breakout board for the BMP085 barometeric pressure sensor chip, if you wish to use it without a JeeNode. The only thing that is required is a translation of the header signals, DIO is SDA and AIO is SCL.

The JeeNode I2C bus, running at 3.3V, is used as interconnect, with all the power and signal lines brought out to both sides of the board to allow daisy-chaining with other 3.3V I2C devices if need be.

The pre-assembled version comes with the SMD-sized BMP085 chip and decoupling capacitor already soldered onto the board. A 6-pin male header is included in the package, but not soldered.

Note that headers may be soldered on in either direction (parts up or down), just be sure and match the pins up with their proper signals on the JeeNode or microcontroller.

The PCB only variant contains just the board for the Pressure Plug.

Applications
Barometer and weather stations
Enhancement of GPS navigation
Altimeter
Elevator floor sensor

Resources
BMP barometric pressure sensor datasheet
The example sketch for a JeeNode is contained in the JeeLabs “Ports” library
Get it here.
JeeLabs pressure plug docs
JeeLabs blog entry