diff --git a/test/dfu/README b/test/dfu/README
index 5176aba..408d559 100644
--- a/test/dfu/README
+++ b/test/dfu/README
@@ -26,12 +26,19 @@
    setenv dfu_alt_info dfu_test.bin fat 0 6\;dfudummy.bin fat 0 6
    dfu 0 mmc 0
 2. On the host:
-   test/dfu/dfu_gadget_test.sh X Y  [test file name]
+   test/dfu/dfu_gadget_test.sh X Y [test file name] [usb device vendor:product]
    e.g. test/dfu/dfu_gadget_test.sh 0 1
    or
    e.g. test/dfu/dfu_gadget_test.sh 0 1 ./dat_960.img
+   or
+   e.g. test/dfu/dfu_gadget_test.sh 0 1 0451:d022
+   or
+   e.g. test/dfu/dfu_gadget_test.sh 0 1 ./dat_960.img 0451:d022
 
 ... where X and Y are dfu_test.bin's and dfudummy.bin's alt setting numbers.
 They can be obtained from dfu-util -l or $dfu_alt_info.
 It is also possible to pass optional [test file name] to force the script to
 test one particular file.
+If many DFU devices are connected, it may be useful to filter on USB
+vendor/product ID (0451:d022).
+One can get them by running "lsusb" command on a host PC.
diff --git a/test/dfu/dfu_gadget_test.sh b/test/dfu/dfu_gadget_test.sh
index 2f5b7db..9c79422 100755
--- a/test/dfu/dfu_gadget_test.sh
+++ b/test/dfu/dfu_gadget_test.sh
@@ -45,18 +45,18 @@
     printf "$COLOUR_GREEN ========================================================================================= $COLOUR_DEFAULT\n"
     printf "File:$COLOUR_GREEN %s $COLOUR_DEFAULT\n" $1
 
-    dfu-util -D $1 -a $TARGET_ALT_SETTING >> $LOG_FILE 2>&1 || die $?
+    dfu-util $USB_DEV -D $1 -a $TARGET_ALT_SETTING >> $LOG_FILE 2>&1 || die $?
 
     echo -n "TX: "
     calculate_md5sum $1
 
     MD5_TX=$MD5SUM
 
-    dfu-util -D ${DIR}/dfudummy.bin -a $TARGET_ALT_SETTING_B >> $LOG_FILE 2>&1 || die $?
+    dfu-util $USB_DEV -D ${DIR}/dfudummy.bin -a $TARGET_ALT_SETTING_B >> $LOG_FILE 2>&1 || die $?
 
     N_FILE=$DIR$RCV_DIR${1:2}"_rcv"
 
-    dfu-util -U $N_FILE -a $TARGET_ALT_SETTING >> $LOG_FILE 2>&1 || die $?
+    dfu-util $USB_DEV -U $N_FILE -a $TARGET_ALT_SETTING >> $LOG_FILE 2>&1 || die $?
 
     echo -n "RX: "
     calculate_md5sum $N_FILE
@@ -89,13 +89,17 @@
 TARGET_ALT_SETTING=$1
 TARGET_ALT_SETTING_B=$2
 
-if [ -n "$3" ]
+file=$3
+[[ $3 == *':'* ]] && USB_DEV="-d $3" && file=""
+[ $# -eq 4 ] && USB_DEV="-d $4"
+
+if [ -n "$file" ]
 then
-	dfu_test_file $3
+	dfu_test_file $file
 else
-	for file in $DIR*.$SUFFIX
+	for f in $DIR*.$SUFFIX
 	do
-	    dfu_test_file $file
+	    dfu_test_file $f
 	done
 fi