This project was forked from the ArduinoCore-samd project which supports the Arduino core for the SAMD21 family of processors. The code has been refactored to support the SAMD20 family of processors, and has also been altered with low power projects in mind.

sudo apt install unzip

Run make help for all make options Open the config.mk file and adjust the DL_DIR path if necessary, default is just a folder inside the repo called dl. You can also adjust the Atmel DFP and CMSIS core versions from this file.

make distclean
make

If you don't want to re-download the DFP and CMSIS distro, just run make clean and then make to rebuild from the arduino source files.

Note for Ubuntu 18.04 : sudo might have to issued with the make commands for it to work. If rebuilding, it is worth issuing sudo make distclean instead of just sudo make clean as one can face core_cm0plus.h: No such file or directory error