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Lighting Networks 101. Digital Multiplex Protocol or ANSI E1.11 – 2004 USITT DMX512-A Asynchronous Serial Data Transmission Standard for Controlling Lighting Equipment and Accessories. DMX. Proper DMX Layout. Daisy Chain the signal path. Console. Fixture or dimmer. Fixture or dimmer.

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Digital Multiplex Protocol


ANSI E1.11 – 2004


Asynchronous Serial Data Transmission Standard for Controlling Lighting Equipment and Accessories

proper dmx layout
Proper DMX Layout

Daisy Chain the signal path



or dimmer


or dimmer


or dimmer

dmx troubleshooting
DMX Troubleshooting

“T” or “Y” connections change the cable impedance causing reflection


or dimmer


dmx mixed layout
DMX Mixed Layout





Each DMX leg out of a repeater is its own electrical entity

Repeaters can be daisy-chained

dmx troubleshooting 2
DMX Troubleshooting (2)‏

Signal path must be terminated with 120 ohm resistor


Terminator switch or plug

on final fixture


or dimmer


or dimmer


or dimmer

Failure to terminate causes signal reflection back up the cable and intermittent problems

dmx cable
DMX Cable
  • Low capacitance required to maintain wave form
  • Belden 9842, 9729, 9829
  • ProPlex, Showplex
  • Cat5, Cat5e, Cat6
  • Not microphone cable
  • What they say about barb wire isn’t true
wave form
Wave Form

Proper square/digital wave form

Sawtooth wave form – likely caused by capacitance in the cable or slew-rating in the transceiver

Wave form overlay (typically caused by reflection)‏

Multiple overlays are possible

dmx data packet
DMX Data Packet


Start Code


Slot 1


also 44uS

Slot 2


1 start bit (low)‏

2 stop bits (high)‏

Mark-after-break 8uS

Break 88uS

Idle time can follow stop bits

dmx data frame
DMX Data Frame

Line Idle - high

2 Stop Bits

- high

1 0 0 1 1 0 1 0

8 Data Bits high or low

1 Start bit

- low

Single Data Frame

11 bits altogether

44uS transmission time

remote device management or ansi e1 20 2006 rdm remote device management over dmx512 a networks
Remote Device Management


ANSI E1.20 - 2006


Remote Device Management

Over DMX512-A Networks

why rdm
Why RDM?

Because DMX isn't enough anymore

  • Too much gear
  • Too many universes
  • Too much paperwork
  • Too many places for things to go wrong
  • Not easy to fix things on the fly
how rdm works
How RDM Works
  • Does not make legacy DMX-only gear obsolete
  • Uses a packet structure, like DMX
  • RDM messages are interleaved or inserted between regular DMX packets
  • DMX does not need to be present for RDM messages to be sent
  • Requires all devices be transmitters as well as receivers
rdm packet structure
RDM Packet Structure

Start Code

Hex CC: indicates RDM Packet

Sub-Start Code

Hex 01: basically for future use

Message Length

Number of slots used by message

Destination UID

UID of intended recipient

Not sure why: only one controller allowed

Source UID

Transaction #

Used to match query and response

Port ID/Response Type

Identifies controller's sending port and responder's type of message

Message Count

Incremented by responder – tells controller number of queued msgs


IDs device within responder ie dimmer within the rack

Message Data

Payload! At last!


16-bit checksum of all above fields

rdm message block
RDM Message Block

Command Class

Get, Set or Discovery

Parameter ID


i.e.: Network Mgmt, Status, Sensors, DMX512 Set-up, others, or manufacturer specific

Parameter Data


Number of slots used by next part of message (can be zero)‏

- responder needs to know when check sum begins

Parameter Data

Format depends on the PID

new rules for system design
New Rules for System Design
  • No more than 4 in-line devices between a responder and the controller
    • In-line devices include opto-splitters, mergers, repeaters, anything that reprocesses the signal
  • In-line devices must be bi-directional
  • Timing changes to DMX E1.11
  • Break time extended to 132uS
  • Each in-line device to reduce break by 22uS
legacy equipment
Legacy Equipment
  • DMX distribution gear developed prior to 2000 will likely need to be replaced
    • no provision for bi-directional signal
    • end gear will depend on manufacturer
  • as purchasers you should be demanding support for older gear
  • DMX-over-Ethernet likely will be okay
  • currently no programming consoles with RDM
rdm and pathway
RDM and Pathway
  • Support for firmware upload over RDM
  • DMX/RDM over Ethernet via Pathport
  • In-line Devices:
    • DMX Repeater Pro
      • Bi-directional opto-splitter
      • Can also act as a controller
        • eDIN 1009 RDM opto-splitter
  • Responder Devices:
        • EDIN 1003 DMX to Contact Output
    • eDIN 1004 DMX-to-Analog
    • eDIN 1006 Analog-to-DMX
    • eDIN 1008 DMX LED Driver
ansi e1 17 2006 architecture for control networks
ANSI E1.17 – 2006

Architecture for Control Networks

remaining problems
Remaining Problems

- sheer size of lighting installations (think LED) causing infrastructure problems

- cost of wire and connectors for DMX/RDM

- management tools not covered by RDM

- multiple universe management

- distribution management (merge, priority)‏

- everything still mapped to 512 channels

- maybe the answer is... Ethernet?

ethernet advantages
Ethernet Advantages

- Cheap wiring and distribution gear

- available everywhere

- 10 Mbit = 40 universes at 250 baud

(we get back to this one)‏

- flexibility of star wiring

- cheap (did I mention cheap?)‏

proprietary protocols again
Proprietary Protocols(again)‏

Strand Shownet

ETC Net1

ETC Net2



....and less often






... and none can talk to each other

dmx over ethernet advantages
DMX-over-Ethernet Advantages
  • signal management

- merging, splitting, priority switching

  • unlimited outputs (dependent on network architecture)‏
  • up to 128 universes of input (typical 2008)‏
  • number of fully active universes varies from protocol to protocol but typically 12 - 15
ethernet limitations
Ethernet Limitations
  • finicky installations
  • sensitive to electrical interference
  • not robust (compared to Belden/XLR)‏
  • 100m cable runs versus 500m for DMX
enter acn
Enter ACN
  • media agnostic – use whatever cable you want
  • intended as a generic language to control devices
  • allows for plug and play
alphabet soup 1
Alphabet Soup (1)‏

CID – Component IDentifier

DDL – Device Description Language

DMP – Device Management Protocol

SDT – Session Data Transport

RLP – Root Layer Protocol

Three letter acronyms – not just for audio anymore

alphabet soup 2
Alphabet Soup (2)‏

CID – Component IDentifier

- unique identifier for each device on system

DDL – Device Description Language

- an XML file describing device properties and associated ‘behaviours’

- controller can pick and choose what it wants depending on sophistication and need

alphabet soup 3
Alphabet Soup (3)‏

DMP – Device Management Protocol

- how to get and set properties of the device

SDT – Session Data Transport

- heart of ACN

- allows efficient, reliable (error-checking) data transmission to one, a few or all devices on the network, depending on need

- created specifically with the typically assymmetric lighting data flow in mind

acn overview
ACN Overview

- information not bound by 512 data slots

- formatted or configured according to need

- device reports native resolution

- end devices can report abilities, parameters to the controller

- no searching for libraries anymore

- configuration using terms that make sense to the user

- devices not limited to lighting equipment

how will it fit together
How Will it Fit Together?

- Ethernet backbone carrying ACN signals

- some devices such as media servers, dimmer banks and LED drivers will sit natively on the network

- gateway nodes will provide ACN-RDM control over configurable devices

- gateway nodes will provide ACN-DMX control over legacy and 'dumb' gear

what s on the shelf now
What’s on the shelf now?

- DMX, obviously

- RDM, increasingly

- streaming ACN Ethernet protocol is available as Net3 (ETC), sACN (Pathway) and soon others (MA Lighting, Pharos)‏

- in the near term (5 years or less) sACN will replace the proprietary protocols

- openACN group working on open source code modules (‏

ethernet design tips 1
Ethernet Design Tips (1)‏

- structured wiring

- IDC termination

- TIA/EIA-568 certification

- Cat5e vs Cat6

-STP and conduit

- observe cable lengths

- max 90m for copper

- copper versus fibre

ethernet design tips 2
Ethernet Design Tips (2)‏

- Power-over-Ethernet (802.3af)‏

- device classes and sufficient power

- switches vs routers

- current lack of Etherner protocol converters

troubleshooting 1
Troubleshooting (1)‏

- managed vs unmanaged switches

- bad things, maybe:

- broadcast storm control

- IGMP packet sniffing

- multicast filtering

- spanning tree protocol

troubleshooting 2
Troubleshooting (2)‏

- maximum traffic for 10Mb devices

- 24 universes for broadcast protocols

- traffic patterns

- Ethernet component reliability issues

- RJ45 vs Ethercon vs XLR

- segregated traffic


- media converters