Understanding Art-Net

While Artistic License publishes a detailed specification on the Art-Net protocol, I found very little additional documentation on the internet - including YouTube, to help configure an Art-Net fixture and light board to talk to one another.  So here is some info I'd like to share.

The light board we are using in this example is an ETC ION.  The fixture is an Elation SIXBAR 500.

First of all, the light board's network interface was already configured on a Class C network (192.168.0) with a wireless access point for use by ETC's iRFR iPad/iPhone app.  Users would use the app to do dimmer checks or advance through cues.

Since Art-Net uses the same network interface, it's best to reconfigure that Class C network to a Class A.  Art-Net defaults to the 2.0.0.0/8 network.  Anything on that network, including the wireless access point (and its associated DHCP pool) would need to be reconfigured accordingly.

ETC ION configuration:
IP Address: 2.0.0.2
Subnet Mask: 255.0.0.0
Art-Net Broadcast: Primary Art-Net
Art-Net Start: 1

Art-Net Start of 1 was necessary in our configuration because Art-Net universes are zero-based and ETC ION universes are one-based.  So in order for ETC ION universe 3 to equal Art-Net universe 3 the "Art-Net Start" should be set to offset by 1.

The Elation SIXBAR 500 uses Art-Net 2 not 3, so it only supports 256 Art-Net universes.  Basically if a fixture doesn't have configuration options for Art-Net 3 "Net" and "SubNet" then it is Art-Net 2.

The SIXBAR's "Universe" and "DMX Address" settings determine which Art-Net universe and channel it responds to.  Leave its IP and CTR addresses at 0.0.0.0 and it will automatically give itself a 2.x.y.z address in compliance with the Art-Net self-addressing specification.  In 43-channel mode, the SIXBAR set to Universe 3, DMX Address 101 is controllable from the ION (if configured as specified above) as 3/101-143.

Update:
I have found that either the Elation eNode or SIXBAR seems to have a firmware bug related to the Universe setting. With ION Art-Net Start of 1 the SIXBAR Universe=ION Universe but the eNode Universe=SIXBAR/ION Universe-1. With ION Art-Net Start of 0 the eNode Universe=ION Universe but the SIXBAR Universe=eNode/ION Universe+1. Without a third Art-Net device from another manufacturer for testing I am uncertain which product's universe selection is off by one.

Understand that Art-Net's Net, Subnet, Universe, Address and value data are all sent out over UDP port 6454 broadcasts.  They have nothing to do with the IP Address or Subnet mask of the network, fixtures or lighting desk.  As long as all the devices are on the same 2.0.0.0/8 network everything will just work.

In my environment the ETC ION was connected to a "control network" with other systems such as a Mac running QLab and a Soundcraft Expression mixing console.  All of these systems are controllable from a variety of iPad/iPhone apps using the wireless access point.  The problem is that Art-Net's chatty traffic may interfere with HiQnet - I had to separate HiQnet from Dante a while back otherwise the Soundcraft Visi Remote app would not work well with the mixing console.  If this is your situation as well, I suggest placing a router between the Art-Net network of 2.0.0.0/8 and the "control network" of 192.168.0/24 so that Art-Net broadcasts do not cross over to the "control network."

While implementing this solution, I discovered that iOS devices do not like to talk to private networks using public address space (2.x.y.z) so it was necessary to configure the router to NAT a private IP on the booth control network (192.168.0.20) to the new IP address of the ETC ION (2.0.0.2). I went with the Ubiquiti EdgeRouter ERLite-3 which is an inexpensive yet powerful three-port router with keyholes for easy backboard mounting.