Lighting Networks 101
DMX
Digital Multiplex Protocolor
ANSI E1.11 – 2004USITT DMX512-A
Asynchronous Serial Data Transmission Standard for Controlling Lighting Equipment
and Accessories
Proper DMX Layout
Console
Fixtureor dimmer
Fixtureor dimmer
Fixtureor dimmer
Daisy Chain the signal path
DMX Troubleshooting
Console
Fixtureor dimmer
“T” or “Y” connections change the cable impedance causing reflection
DMX Mixed Layout
Console
Console
Merger
Opto-splitter/Repeater
Each DMX leg out of a repeater is its own electrical entity
Repeaters can be daisy-chained
DMX Troubleshooting (2)
Console
Fixtureor dimmer
Fixtureor dimmer
Fixtureor dimmer
Signal path must be terminated with 120 ohm resistor
Terminator switch or plugon final fixture
Failure to terminate causes signal reflection back up the cable and intermittent problems
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
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
Slot 1(lvl=0)
also 44uS
Start Code
44uS
Slot 2(lvl=0)
Mark-after-break 8uS
Break 88uS
Idle time can follow stop bits
High
1 start bit (low)
2 stop bits (high)
DMX Data FrameLine Idle - high
2 Stop Bits- high
1 Start bit- low
8 Data Bits high or low
1 0 0 1 1 0 1 0
Single Data Frame11 bits altogether44uS transmission time
RDM
Remote Device Managementor
ANSI E1.20 - 2006RDM
Remote Device ManagementOver DMX512-A Networks
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
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
Start Code
Sub-Start Code
Message Length
Destination UID
Source UID
Transaction #
Port ID/Response Type
Checksum
Message Count
Sub-device
Message Data
Hex CC: indicates RDM Packet
Hex 01: basically for future use
Number of slots used by message
UID of intended recipient
Not sure why: only one controller allowed
Used to match query and response
Identifies controller's sending port and responder's type of messageIncremented by responder – tells controller number of queued msgsIDs device within responder ie dimmer within the rack
Payload! At last!
16-bit checksum of all above fields
RDM Message Block
Command Class
Parameter ID(PID)
Parameter Data Length
Parameter Data
Get, Set or Discovery
i.e.: Network Mgmt, Status, Sensors, DMX512 Set-up, others, or manufacturer specific
Number of slots used by next part of message (can be zero)- responder needs to know when check sum begins
Format depends on the PID
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
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 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
ACN
ANSI E1.17 – 2006Architecture for Control Networks
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
- 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)
Strand ShownetETC Net1ETC Net2
ArtNetPathport
....and less oftenAVAB
CompuliteEnttec
ColornetKiNet
... and none can talk to each other
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
finicky installations
sensitive to electrical interference
not robust (compared to Belden/XLR)
100m cable runs versus 500m for DMX
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)
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)
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)
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
- 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?
- 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?
- 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 (www.openacn.org)
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)
- Power-over-Ethernet (802.3af)
- device classes and sufficient power
- switches vs routers
- current lack of Etherner protocol converters
Troubleshooting (1)
- managed vs unmanaged switches
- bad things, maybe:
- broadcast storm control- IGMP packet sniffing- multicast filtering- spanning tree protocol
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-VLANS
- media converters