diff --git a/artiq/frontend/lda_controller.py b/artiq/frontend/lda_controller.py
index 8efc3cbb4..cc70038e9 100755
--- a/artiq/frontend/lda_controller.py
+++ b/artiq/frontend/lda_controller.py
@@ -15,7 +15,11 @@ def get_argparser():
                         choices=["LDA-102", "LDA-602"])
     simple_network_args(parser, 3253)
     parser.add_argument("-d", "--device", default=None,
-                        help="USB serial number of the device."
+                        help="USB serial number of the device. "
+                             "The serial number is written on a sticker under "
+                             "the device, you should write for example "
+                             "-d \"SN:03461\". You must prepend enough 0 for it "
+                             "to be 5 digits."
                              " Omit for simulation mode.")
     verbosity_args(parser)
     return parser
diff --git a/doc/manual/ndsp_reference.rst b/doc/manual/ndsp_reference.rst
index d7e454126..c0f619f86 100644
--- a/doc/manual/ndsp_reference.rst
+++ b/doc/manual/ndsp_reference.rst
@@ -34,6 +34,28 @@ Client
 Lab Brick Digital Attenuator (LDA)
 ----------------------------------
 
+On Linux, you need to give your user access to the usb device.
+
+You can do that by creating a file under /etc/udev/rules.d/ named 99-lda.rules
+with the following content::
+
+    SUBSYSTEM=="usb", ATTR{idVendor}=="041f", MODE="0666"
+
+Then you need to tell udev to reload its rules::
+
+    $ sudo invoke-rc.d udev reload
+
+You must also unplug/replug your device if it was already plugged in.
+
+Then, to run the Lab Brick Digital Attenuator (LDA) controller::
+
+    $ lda_controller -d SN:xxxxx
+
+The serial number must contain 5 digits, prepend any number of 0 necessary.
+Also, the "SN:" prefix is mandatory.
+
+You can chose the exact LDA model with the -P parameter. The default being LDA-102.
+
 Driver
 ++++++