Open Lighting Architecture: Blinky Lights! Matt Ranostay

mranostay@gmail.com

Brief OverviewNot an expert in industrial lighting systemsCurrently a pet project aka weekend beer

codingAny questions unable to answer can be

addressed to the #openlighting channel on Freenode

Crash course on lighting systemsSpeaker talks fast so interrupt him if you

don’t understand somethingBTW who doesn’t like blinky lights?!?!

DMX? Not just a rapper?DMX512 (Digital Multiplex 512) is an

industry standard lighting specification that has been in use since 1986 (literally as old as me)Any light show, rave, concert, and misc events

you have been too has certainly used this technology

RS-485 is the transport medium usedXLR-3 or XLR-5 (typical) connector

Differential pair + Ground XLR-5 has two un-used or unassigned pins

DMX RS-485 TrafficDMX512 is named so because it is 512 slots of

data + 1 command/start code slotSlot is one byteEach of these groups is called an universe

Specification allows up to 44 fps, but can piped out faster if not all slots are used.Most vendors stick to 44 fps though

Commands can control panning, light intensity, etc

Slots can be combined to increase range from 8-bits to 16, 32, etc bits.

DMX512 RS-485 ProtocolRS-485 has no clock line so you need a set

way to know when a frame beginsMust be terminated for the bias network to

work (120 ohm)DMX512 signals a start of frame

Break of 100 microseconds Mark After Break (MAB) 12 microseconds Followed with 11-bit sequence for each slots

Start bit + 8 bits of data + 2 stop bits.

DMX512 Oscilloscope Output

Example of DMX-enabled DevicesStage Lighting (vast majority of applications)

LasersRGB LED panels (i.e. 16x16 grids)RGB LED stringsServo controlled light mounts (Pan + Tilt)

DimmersHaze / Fog Machines Niche market of animatronics

Halloween decorations

DMX in action (Singapore Flyer)

DMX-over-IPVarious implementations over the years that

have all have pros and consArtNet IIIE1.31 – Streaming ACN

De facto solution used for large lighting shows 63,999 universes allowed per IP ANSI + PLASA/ESTA approved standard

DMX specification doesn’t reference any networking protocols, but all of the major ones wire protocol mirror the RS-485 data schema

Typically used over Ethernet

Remote Device ManagementRDM was designed after DMX512 and uses

the same RS485 path to send messagesBi-directional controlling and status messagesBackwards compatible with legacy DMX

devicesUses start code 0xCC and encapsulates data

within this

Open Lighting Architecture Completely Open Source implementation of

the networking aspects of the DMX512 protocolOLA protocol for Python bindingsOpen Sound Control (OSC)ArtNet III + E1.31 sACN

Various plugins for interfacing to devicesVendor specific plugins SPIUSB DMX devices

Open Lighting ArchitectureFuture support for RS-485 array of devices

on Linux is planned which will make this more of network to DMX512 bridgeCheap low end development board then can be

a bridgeRemote Device Management (RDM) is fully

supported and robustLighting control panels or various control

devices Currently have no hardware that uses RDM so

I’ve never used it

OLA Web Interface

Typical OLA Setup

OLA HacksTriggers from DMX control codes that run

commandsCould trigger a processing scriptTurn on or off a relay switch

Python/C++/Java loopback API allows you to send frames locally to a OLA interface

JSON web interface for when other protocols are too much

Open Sound ControlOSC is used for MIDI control as well lighting

controlOLA has a OSC interface that can be used as

wellVarious DMX frontend generators use this for

user inputOpen Lighting ArchitecturePixelController

TouchOSC – iPhone application to OSC systemsVarious other applications exist for Android

and iOS

Data Flow

WS2812 Chipset (self-clocking)

WS2801 (SPI + protocol decode)

OLA + PixelController + AM335x PRU

DemoBeagleBone Black (am335x)

PRU (Programmable Real-time Unit) outputting SPI and/or another self clocked protocol

Open Lighting ArchitectureSPI plugin interacting with faux-spidev

interfacePython interface to directly drive LED string

Conclusions/OpinionsDMX is old but it is a classic has little need to

be improved other than legacy systems being moved to the networking space versus RS-485

Inferior protocols exist for the sheer fact people are lazy to learn something new and figure it is okay to write a new oneOpen Pixel Controller is an example

QuestionsHow many have you used staging light that

has utilized DMX512? Or some other propriety protocol?

Have you used OLA, and how can we improve the project?

What you currently use for your software driven lighting needs?

Special ThanksSimon Newton - nomis52Andrew Frazier - mrpacketheadPantelis Antoniou - panto

References

Open Lighting Architecturehttp://www.openlighting.org

Singapore Flyer Picturehttp://en.wikipedia.org/wiki/

File:The_Singapore_Flyer_at_night.jpgDMX512 Oscilloscope Graph

http://en.wikipedia.org/wiki/File:Annotated_trace_of_DMX-512_signal.png

ReferencesSigrok + Pulseview (WS2801 + WS2812

debug)http://sigrok.org

WS28xx PRU firmwarehttps://github.com/mranostay/ws28xx-lighting-

pruPixelController

https://github.com/neophob/PixelControllerTouchOSC

http://hexler.net/software/touchosc