Uh yea! That's easy to overlook.    I think you want to use         FLASHDEPS += upload-reset      PREFLASHER = $(RIOTTOOLS)/upload-reset/upload-reset      PREFFLAGS = $(PORT) 750    here.    Then you could put `upload-reset.c` into `dist/tools/upload-reset` and add a `Makefile`, like it's done with e.g. [ethos](https://github.com/RIOT-OS/RIOT/tree/master/dist/tools/ethos).