diff --git a/Makefile b/Makefile
index 80d9abc..787cfc2 100644
--- a/Makefile
+++ b/Makefile
@@ -18,7 +18,7 @@
 # be silent per default, but 'make V=1' will show all compiler calls.
 ifneq ($(V),1)
 Q := @
-NULL := 2> /dev/null
+NULL := 1> /dev/null 2> /dev/null
 endif
 
 # the final binary name (without extension)
@@ -94,6 +94,9 @@ OOCD ?= openocd
 OOCD_INTERFACE ?= stlink-v2
 OOCD_TARGET ?= stm32f1x
 
+# which USB CDC ACM port is used bu the device, so we can reset it
+ACMPORT = /dev/ttyACM0
+
 # board specific USB DFU bootloader
 BOOTLOADERS = STM32duino-bootloader
 BOOTLOADER = $(BOOTLOADERS)/STM32F1/binaries/generic_boot20_pa1.bin
@@ -135,7 +138,6 @@ list: $(BINARY).list
 	$(Q)size $(@)
 
 %.o: %.c
-	@#printf "  CC      $(*).c\n"
 	$(Q)$(CC) $(CFLAGS) $(ARCH_FLAGS) -o $(@) -c $(<)
 
 clean:
@@ -156,9 +158,14 @@ flash-swd: $(BINARY).hex
 	$(info flashing $(<) using SWD)
 	$(Q)$(OOCD) --file interface/$(OOCD_INTERFACE).cfg --file target/$(OOCD_TARGET).cfg --command "init" --command "reset init" --command "flash write_image erase $(<)" --command "reset" --command "shutdown" $(NULL)
 
-flash-dfu: $(BINARY).bin
+# reset device by setting the data width to 5 bis on the USB CDC ACM port
+reset:
+	$(Q)stty --file /dev/ttyACM0 115200 raw cs5
+	$(Q)sleep 0.5
+	
+flash-dfu: $(BINARY).bin reset
 	$(info flashing $(<) using DFU)
-	$(Q)dfu-util --device 1eaf:0003 --cfg 1 --intf 0 --alt 2 --reset --download $(<)
+	$(Q)dfu-util --device 1eaf:0003 --cfg 1 --intf 0 --alt 2 --reset --download $(<) $(NULL)
 
 .PHONY: clean elf bin hex srec list bootloader flash flash-swd flash-dfu
 .SECONDARY: