This a gdb interface for arduino zero (atmel D21)
Tested under windows and arduino ide 1.73
- put everything in arduino folder tools/ZeroGDB
- open arduino ide, compile and upload your sketch
- goto Tools->GDB interface in arduino ide and the debug windows should show up
- have fun
here is a greate reference for gdb: http://users.ece.utexas.edu/~adnan/gdb-refcard.pdf