HP03S is a cheap and easy to use pressure sensor. http://www.hoperf.com/sensor/barometer_sensor/HP03S.htm From the Hope page: . Supply voltage 2.2v-3.6v . -40°C to + 85°C operating range . No external components required . Integrated pressure sensor . 300-1100hpa absolute Pressure Range Available for example at Pollin http://www.pollin.de/shop/dt/MDg4OTgxOTk-/Bausaetze_Module/Module/Luftdruck_Modul_HP03S.html Requirements to run =================== Externals: - I2C (see I2C.h) - GPIO pin (see GPIO.h) - system function to wait milliseconds (see Time.h) - 32 kHz on MCLK (not controlled by this module) This is explicit left out for power management of system If needed, an API could be introduced HP03S_Enable/HP03S_Disable which would control MCLK Many of the required interfaces can be implemented as macro depending on your platform if runtime is important. Requirements to build ===================== the build is done with make, tests are done with CppUTest (http://www.cpputest.org). To build and run the tests (for which this Makefile is configured), you need to have installed CppUTest and put it in ../CppUTest or set the environment variable CPPUTEST_HOME. For building with rake, you need ruby, rake and the gem rake-builder.