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DMX Backup

This manual explains how to set up DMX Backup (redundant DMX) on the nodeGBx system (notably Node8GBx) so a DMX line can automatically take over if the chain breaks.

What DMX Backup Does

DMX Backup creates a redundant DMX stream using two ports configured for the same universe, where one port is designated as the backup. If the main DMX chain fails, the backup port begins transmitting so the fixtures keep receiving DMX.

Availability: DMX Backup is available on the nodeGBx system from firmware 1.25.

Required Hardware Topology

You will use: - Two DMX ports on the nodeGBx system - A standard daisy chain of fixtures - A return line from the end of the fixture chain back to the second port (the backup port)

Step-by-Step Setup

  1. Configure 2 ports to the same universe.
  2. Enable DMX Backup on one of the two ports (set that port to DMX backup: Enabled).
  3. Daisy chain the DMX fixtures as usual from the “normal” output port.
  4. Feed the last fixture back into the second port (the backup port).

Result: The DMX run is now redundant.

How Takeover Works

  • The DMX backup port detects whether DMX is present and starts transmitting accordingly.
  • In case of a DMX chain failure, takeover is within 50 ms (maximum 2 DMX frames).
  • When the connection is restored, there can be a maximum “collision” of less than one DMX frame.

Making the Network Segment More Fail-Safe

The application note describes an additional resilience approach:

  • If you use two different nodes on two different switches, you can make “even the last part of the network” more fail-safe by setting the hold time on the normal output node to minimum.
  • If the output node stops receiving the universe but the DMX backup port does receive it, the backup will start transmitting after the DMX Hold time has passed.

Practical takeaway: Hold time influences how quickly backup begins transmitting in scenarios where network delivery differs between nodes.

Front-Panel / Display Status Indicators

The node display can show these statuses:

Output port vs DMX backup port

  • Gray
  • Output: output idle

  • Backup: output idle

  • Green

  • Output: Transmitting DMX

  • Backup: Receiving DMX (OK)

  • Red

  • Backup: Backup Active (DMX Fail)

Monitoring

When the backup becomes active, the DMX backup port reports “Backup Active” to dmXLAN for early detection of a broken DMX link.

Operational tip: Use this status reporting as a trigger for alerts/maintenance—backup is a safety net, but you still want to fix the broken link quickly.

Quick Checklist

  • nodeGBx firmware ≥ 1.25
  • Two ports configured to the same universe
  • One of those ports set to DMX backup: Enabled
  • Fixture chain wired normally, with return from last fixture back to the second port
  • Verify display states: green “Receiving DMX (OK)” on backup during normal operation; red “Backup Active” during failover
  • Optional: tune hold time (especially in multi-node / multi-switch resilient designs)