When no fixture is found

Connecting can stop short in three places: the widget will not open, the line has nobody on it, or a unit answered but could not be listed. Each points somewhere different, so start from what the bench said.

Cabling and RDM

• The widget needs its RDM firmware, version 2. Most ship without it, and the bench refuses to connect until it is flashed: see The wrong firmware.
• Plug the fixture into the widget’s DMX output and power it up. On a bench, one fixture straight off the widget is the usual setup. Put a terminator in the fixture’s DMX output: an unterminated line can make a fixture miss requests.
• RDM has to be on at the fixture, if its menu has a setting for it. Some fixtures switch it off, or only answer it in some modes.

If the widget is not in the port list at all, see Not in the port list.

Nothing answered

No fixtures found means the widget opened, answered and searched the line, and nothing replied. The bench is working. Check, in order:

1. The fixture has power and the DMX cable goes from the widget’s output to the fixture’s input.
2. RDM is on in the fixture’s menu, and its manual says it supports RDM at all. Many budget fixtures do not, whatever the spec sheet says.
3. The line is terminated, and the cable is good. Try a short cable with nothing else on it.

Then choose Fixture → Rediscover (⌘R) (macOS).

Could not be listed

A unit that answered the search but could not be settled appears under Could not be listed, with a sentence on why. Each needs a different fix.

Two fixtures with one UID

A duplicate UID: every reply for it collides with another, so neither unit can be listed or reached over RDM. A cloned control board is the usual cause. A fixture whose search reply is corrupt every time looks the same. To find them, unplug fixtures one at a time and choose Fixture → Rediscover after each, until the search settles. Until one of the two is changed, both misbehave whenever RDM is on.

Never acknowledges the search

The unit answers the search but never confirms it has been counted, so the bench cannot finish listing it. A reply lost on a poor line looks like this, so check the cable and termination and rediscover first. If it persists on a short, terminated cable, the fixture’s firmware is not handling RDM discovery properly.

Never leaves the search

The unit confirms it has been counted, then goes on answering the search anyway. This is the fixture that makes a whole line discover slowly and come back short, because every search keeps finding it and gives up before reaching the units behind it. It is a fault in the fixture’s firmware, not the line. The behavior check names it too.

From the command line

rdmbench-cli widget reads the widget’s firmware, serial number and UID, and works even when the firmware is the DMX-only build, so it is the first thing to try when connecting fails. rdmbench-cli ports lists every serial port, with a * beside those that look like the widget, and --port names the one to use. rdmbench-cli discover searches the line and prints the UID of each fixture found.