Chris Büchner wrote: > avr-gcc mnut03.o -mmcu=atmega128 > -Wl,--defsym=main=0,-Map=mnut03.map,--cref > -LC:/ethernut-4.4.1/nutbld/lib -Wl,--start-group > C:/ethernut-4.4.1/nutbld/lib/nutinit.o -lnutpro -lnutos -lnutdev > -lnutnet -lnutcrt -Wl,--end-group -o mnut03.elf You need to add -lnutarch to your Makefile. Harald