BMP280 - Temperature and Pressure measurement

These are tiny encapsulated modules made by Bosch and are only really practical to use in DIY when assembled on a module pcb board. I know there are some who will make a go of SMD components but not me and not at this size. However it does work very well and is very easy to use, provided the 3.3V supply limit is observed. They have two modes of operation, continuous which repeatedly measures temperature and pressure, providing the last measurement immediately on request, and an on demand which when requested, runs the measurement and provides the results. The former uses power all the time its running, in the latter power consumption is cut in-between measurements. 

For the initial implementation, the module is being run in continuous mode, but will be run in the most appropriate mode when power consumption code is added.

Software to implement these ideas can be viewed on github here