Il tuo sketch non compila su Linux.
Ecco l'errore:
sketch_aug30a.ino: In function ‘void SPI_init()’:
sketch_aug30a:6: error: ‘PB0’ was not declared in this scope
sketch_aug30a:6: error: ‘PB3’ was not declared in this scope
sketch_aug30a:6: error: ‘PB5’ was not declared in this scope
sketch_aug30a.ino: In function ‘void SPI_write16(short unsigned int)’:
sketch_aug30a:23: error: ‘PB0’ was not declared in this scope