RDM

showstack / protocols / rdm

Also called Remote Device Management, E1.20, RDM over DMX.

Bidirectional device management that shares the same pair as DMX512, using alternate start code 0xCC so level data and management traffic interleave on one line. It is how you read and change a fixture's address, personality and sensors without going up in the truss.

Device managementOpenESTAVerified

Stewarded by ESTA (Entertainment Services and Technology Association).

Management Housekeeping, no deadline

Discovery, monitoring, configuration, backups, updates. Useful, and none of it has a deadline of its own.

What kills it. Nothing kills it. That is the problem: with no deadline it has no manners, and it will happily starve everything that does have one. Putting it on a show VLAN is the commonest self-inflicted wound in the industry.

Why this one, and not what the category suggests. Discovery, addressing and configuration sharing the DMX pair. It has no show deadline and it competes with traffic that does — which is exactly why it is scheduled between the lighting frames rather than instead of them.

The four flows, and why the model is worth having →

Addressing

Shares the DMX512 slot space. Devices are addressed by a UID built from a 16-bit ESTA manufacturer ID plus a device-specific part, not by DMX address.

What goes wrong

Every splitter, buffer and opto in the path has to be RDM aware. A one-way splitter passes DMX perfectly and silently swallows every response, so discovery finds nothing and the rig looks dead to the controller.

Fixtures that do not check start codes will act on 0xCC packets as if they were levels. Enabling RDM on a line with old kit on it can produce flicker or jumps that look like a data fault.

RDM traffic occupies slots that would otherwise carry DMX. Heavy discovery or continuous sensor polling measurably drops the refresh rate, so turn the polling down before doors.

Discovery is a binary search over the UID space with collision retries. On a large or marginal line a full discovery takes minutes and can still miss devices; run it twice before believing the count.

The controller owns the line. Two RDM controllers on the same universe talk over each other and responses get attributed to the wrong device, which produces genuinely confusing patch data.

Manufacturer IDs 8000h to FFFFh are reserved for the dynamic UIDs used by E1.33 RDMnet. A device showing one of those is not identifiable by manufacturer from the UID alone.

Response timing is tight and specified. A long line, a bad terminator or a cheap USB dongle that turns the driver around too slowly will produce intermittent discovery with clean-looking DMX.

What speaks RDM (32)

32 products — 23 hardware, 9 softwareshow all

Product	Direction	Notes
Avolites Titan Avolites	bidirectional	Patching by RDM requires an RDM-enabled Art-Net node. The console's own XLR connectors do not support RDM.
ChamSys MagicQ ChamSys	bidirectional	RDM is listed among the features available in demo mode, so it does not need a wing or dongle.
DMX-Workshop Singularity (UK) Ltd	bidirectional	RDM over Art-Net discovery/control.
DMXcat City Theatrical, Inc.	bidirectional	RDM Controller app performs RDM discovery, listing devices/addresses/attributes, via the DMXcat hardware.
Eos Electronic Theatre Controls (ETC)	bidirectional	Device discovery from the Patch display. Network RDM requires an ETC Net3 or Response Mk2 gateway with RDM enabled on the DMX ports, running gateway software 5.1 or newer.
ETCDmxTool ETC Labs	bidirectional	Acts as an RDM controller and can capture RDM traffic; full feature set requires ETC Gadget II hardware.
OLA (Open Lighting Architecture) Open Lighting Project	bidirectional	OLA carries a full RDM responder and controller stack.
RDM Controller JESE	bidirectional	Full RDM discovery, GET and SET.
Wireshark Wireshark Foundation	in	E1.20 RDM dissector; base fields since Wireshark 1.8.0, extended fields since 3.4.0.
Avolites Diamond 9 Avolites	bidirectional	RDM discovery and patch from Titan.
Avolites Tiger Touch III Avolites	bidirectional	RDM from Titan.
ChamSys MagicQ MQ80 ChamSys	bidirectional	Through supported nodes and outputs.
ChamSys MagicQ MQ500M Stadium ChamSys	bidirectional	Discovery and parameter setting from the console.
City Theatrical Multiverse Transmitter City Theatrical	bidirectional	Wireless RDM.
ELC dmXLAN node8 ELC Lighting	bidirectional	Depending on model and firmware.
ENTTEC DIN Ethergate MK2 ENTTEC	bidirectional	Depending on firmware.
ENTTEC DMX USB Pro ENTTEC	bidirectional	Requires the DMX/RDM firmware; ENTTEC also supplies separate DMX-only firmware.
ENTTEC ODE Mk3 ENTTEC	bidirectional	ANSI E1.20 RDM.
Eos Apex 5 ETC	bidirectional	RDM data is carried over Art-Net and over ETC Net3.
ETC Eos Apex 10 ETC	bidirectional	Through Net3 gateways.
ETC Ion Xe 20 ETC	bidirectional	RDM through Net3 gateways.
ETC Response Mk2 DMX/RDM Gateway ETC	bidirectional	RDM proxy for discovery and configuration from the console.
ETC Sensor3 Dimmer Rack ETC	bidirectional	RDM for module reporting on supported configurations.
ETC ThruPower Rack ETC	bidirectional	Configuration and feedback.
grandMA2 full-size MA Lighting	bidirectional	RDM on the local DMX ports.
MA Lighting grandMA3 light MA Lighting	bidirectional	Fixture discovery and configuration.
LumenRadio CRMX Nova TX2 LumenRadio	bidirectional	Bidirectional RDM over the wireless link.
Luminex LumiNode 12 Luminex Network Intelligence	bidirectional	RDM discovery and proxy.
Obsidian Control Systems NX4 Obsidian Control Systems	bidirectional	RDM discovery on the local ports.
Pathway Connectivity Pathport OCTO Pathway Connectivity	bidirectional	Discovery and configuration.
Wireless Solution W-DMX BlackBox F-2 G6 Wireless Solution	bidirectional	RDM over the wireless link.
Zero 88 FLX S48 Zero 88	bidirectional	RDM on the local DMX ports.

Open source implementations

OLA (Open Lighting Architecture) — C++, LGPL-2.1-or-later
ETCLabs RDM — C, Apache-2.0

Typical use

Reading and setting DMX addresses and personalities from front of house
Pulling lamp hours, temperature and error sensors during a preshow check
Identifying which physical fixture sits on which address
Configuring gateways, splitters and dimmer racks on a DMX line

The words for it

Glossary entries that name RDM, with the false friends that catch people out.

RDM proxyRDM 代理裝置An RDM device that responds on behalf of others, holding a list of the UIDs behind it so a controller can be …RDM sub-deviceRDM 子裝置A logical device inside one physical RDM device, addressed by number so that a multi-channel product can expo…

Sources

ANSI E1.20 — Remote Device Management over DMX512 Networks (current edition, free download) — ESTA Technical Standards Program primary
ANSI E1.20-2010 preview — scope, half-duplex operation, DISC_UNIQUE_BRANCH discovery — ESTA / ANSI webstore primary
DMX512 Alternate START Codes registry (0xCC = E1.20 RDM) — ESTA Technical Standards Program primary
ESTA Manufacturer IDs (16-bit ID, 8000h-FFFFh reserved for E1.33 dynamic UIDs) — ESTA Technical Standards Program primary

Understand the mechanism

DMX on the wire Show networks How a one gets down a wire

Something wrong, or missing?

Known gaps on this entry: default_ports. If you can source one of them, that is a ten minute pull request.

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