hi tamas sorry, didn't see your output. i guess its the avr-libc-1.2.3 which is causing your problems. nut/os is not really keeping pace with frequent changes of avr-libc lately. just go back and try avr-libc-1.0.4 and try again. avr-lic-1.0.5 needs a patch but you can find it in the mail archive of nut/os. matthias