DMX node
DMX Tester
Light one channel, slot or fixture at a time to find out which is which
Inputs
| Port | Type | Default |
|---|---|---|
| EnableOff sends a dark frame rather than nothing, so the rig goes out instead of holding the last thing it was told. | bool | true |
| ModeHold keeps one target live and Target chooses it — that is the switch. Walk steps through Count of them at Rate, so you can watch which lamp is which. All lights every one at once. Off blacks the rig out. | int | 1 |
| TargetWhich channel, slot or fixture is live in Hold mode. Counted from 1 and clamped to what fits in a universe, so a number past the end lights the last one rather than nothing. Cable it from a Counter or a slider to sweep the rig by hand. | int | 1 |
| UnitWhat Target counts. Channel is one DMX channel. Slot is a high/low pair, the way a 16-bit pixel fixture spends two channels on one colour. Fixture is every channel of one lamp at once, which is what makes it unmistakable across a room — Width says how many that is. | int | 2 |
| WidthChannels per fixture, used only when Unit is Fixture: RGBW 8-bit is 4, RGBW 16-bit is 8, plain RGB is 3. Fixture 3 at a width of 8 is channels 17-24. Check it against the Maximum Pixels figure on your controller: one universe divided by that number is the width. | int | 4 |
| CountHow many channels, slots or fixtures a Walk covers before starting over, and how many All lights. Clamped to what fits in a universe. | int | 8 |
| LevelBrightness of whatever is live, 0 to 1, sent as a DMX byte. Full is usually what you want while identifying a rig. | float | 1 |
| RateSteps per second in Walk mode. 1 Hz is easy to follow by eye; 0 stops the walk and holds Target instead. The step is a pure function of the patch clock, so it never drifts. | float | 1 |
Outputs
| Port | Type |
|---|---|
| Universe Data | structure |
| Current | int |
| Changed | bool |
How It Works
Art-Net cannot ask a rig what it has, and plenty of controllers never answer a discovery poll at all — a search comes back empty from an installation that is working perfectly. The reliable way to learn which lamp is which, and how many channels sit between two of them, is to light them one at a time and watch. That is this node.
It builds a whole DMX frame every frame and hands it to a DMX Sender through Universe Data. Four modes decide what is in that frame:
| Mode | What happens |
|---|---|
| Hold | One target stays lit, chosen by Target — turn the number and a different lamp lights |
| Walk | Steps through Count targets at Rate steps per second, so the rig identifies itself |
| All | Lights every one of them at once |
| Off | Sends a dark frame — not an empty structure, so the fixtures actually go out instead of holding the last thing they were told |
Unit is what makes this usable on a pixel rig. A Channel is one DMX channel; a Slot is the high/low pair a 16-bit fixture spends on one colour, the way DMX Channel Map means it; a Fixture is every one of its Width channels lit at once. Fixture 3 at a width of 8 is channels 17-24, not channel 3 — which is exactly the arithmetic you do not want to be doing on a ladder.
The walk is a pure function of the shared patch clock rather than an accumulator, so scrubbing Rate while it runs never desyncs it.
Parameters in Depth
Enable (bool, default true) — off behaves like Off mode: a dark frame, so the rig goes out rather than freezing on the last lit target.
Mode (int, default Walk) — Hold · Walk · All · Off.
Target (int, default 1) — which one is live in Hold mode, counted in whatever Unit is set to. It is clamped to what fits in a 512-channel universe.
Unit (int, default Fixture) — Channel · Slot · Fixture. A Slot spans two channels, a Fixture spans Width.
Width (int, default 4) — channels per fixture, so 3 for an RGB head, 4 for RGBW, 8 for a pixel block. It only matters when Unit is Fixture.
Count (int, default 8) — how many targets Walk and All cover. It is clamped to the number that fit in the universe at the current span.
Level (float, default 1, range 0…1) — how bright the lit target is; the value is written as a DMX byte of 0…255.
Rate (float, default 1, range 0…20) — Walk steps per second. At 0 the walk stops on Target, which makes Rate a live dial between "step for me" and "let me pick".
The outputs tell you what you are looking at: Current is the target that is lit right now (0 means "no single one" — All or Off), and Changed is a one-frame pulse on each step.
Typical Patches
- Identify the rig: DMX Tester (Walk, Unit Fixture, Width 8, Count 8) → DMX Sender, with Current → UI Text on the output window — the number is on screen while the lamp is lit, so you never have to count along.
- Find an address: Unit Channel, Mode Hold, and a slider or the arrow keys into Target — walk the universe one channel at a time until the fixture you are looking at responds.
- Check a 16-bit head: Unit Slot isolates the high/low pair a colour occupies, which is what DMX Channel Map addresses.
- Blackout button: a Keyboard or MIDI toggle into Enable — off sends a dark frame, so it is a real blackout rather than a stopped stream.
- Step a lighting cue: Changed into a Counter or a Do Once advances something else in the patch on every walk step.
Open DMX Tester in the interactive catalog →
DMX Tester is one of 381 nodes in Grafit Pro.
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