Each directory is its own project with its
own readme, hardware requirements, build/, src/, etc...
To build a project just run make <dirname> DEVICE=<device name>
;
For example my project test/, uses an arduino uno r3 which is
represented as ttyACM0 in my /dev/ directory
make TEST DEVICE=/dev/ttyACM0
will compile test/src/ > test/build/test.hex and flash it
to $(DEVICE).
The make flag for each project is its dirname capitalized.