BOARD_TYPE files are used to identify the type of Arduino board that for which we will be compiling, within a given directory.
It consists of a single line that identifies an Arduino board. Some boards with CPU-variants are further identified by a cpu-variant name in the form BOARD.CPU_VARIANT, eg pro.8MHzatmega168.
The board names are derived from boards.txt files that are distributed with Arduino software.
To see the list of possible boards use:
$ dno_bpp -t
To create a BOARD_TYPE file use:
$ dno BOARD_TYPE BOARD=<BOARD_NAME>
eg:
$ dno BOARD_TYPE BOARD=uno