# Light a fixture with Send DMX

- **MCP resource:** rdmbench://help/send-dmx
- **Version:** 0.2.0
- **Runs on:** macOS 15 Sequoia or later, Apple silicon or Intel
- **Needs:** An Enttec DMX USB Pro with its DMX/RDM firmware (major version 2)
- **Price:** Free

Send DMX puts levels on the line and holds them, so you can see the
fixture work while you read it: prove what a channel does, confirm a
new address by lighting it, or load the fixture while the monitor
watches its temperature. The levels stay up through every RDM request
the bench makes, until you release them.

## Opening it

Select the fixture and choose **Fixture → Send DMX…** (⇧⌘K) *(macOS)*,
or right-click it in the sidebar. Channels are numbered the fixture's
way, from 1 at its start address, as its manual numbers them. The
**DMX** column beside each one is where it lands on the line. When the
two disagree with the desk's patch, that is often the fault.

## The channel list

There is one row per channel. Where the rows come from changes what
they start at:

- **The fixture reports a slot table.** Each row is named by the
  fixture and starts at the fixture's own default. Raise the channels
  you want and leave the rest resting. *standard name* beside a row
  means the fixture gave no name of its own, and the standard's name
  for that kind of slot is shown.
- **The bench has a profile for the model.** Names, what each range of
  a channel does, and starting levels come from the model's profile,
  written down from its manual. *profile* beside a name says so.
- **Neither.** Rows are just "Channel 1", "Channel 2" and so on. Nothing
  is sent for a channel until you set it. The manual says which ones to
  raise: usually a dimmer, and not a macro or strobe channel.

Each row has a slider, **0**, **50** and **Full**, and a button to put
it back where it started. **Reset All** puts every row back.

## Every channel at one level

The switch at the top sends one level to every channel of the fixture.
It is quick, and it can mislead: full on a color-macro channel is a
macro, not white. One fixture lit **UV only** this way. When a fixture
lights in an unexpected color, set channels one at a time instead.

## Hold, Done and Release

**Hold** puts the levels up. From then on, every change in the sheet
goes straight to the fixture.

- **Done** closes the sheet and leaves the levels up, so you can take
  a report, monitor or walk around the fixture. A banner says what is
  being held. **Adjust…** on the banner reopens the sheet where you
  left it.
- **Release** ends output and leaves the line as it was before.
- **Cancel**, before anything is held, closes the sheet having sent
  nothing.

## The frame

By default the frame ends at the fixture's last channel rather than
running to 512, because some fixtures miss RDM requests while a long
frame is on the line. Anything patched past that point sees no signal.

Under **Frame**, **Full frame** sends all 512 slots, as a desk does. If
the fixture stops answering RDM with it on and answers with it off,
this unit misses requests under a long frame.

## From the command line

`rdmbench-cli dmx --fixture 1=255 7=255 8=40` holds those channels of
the first fixture found, counted from its start address, until Ctrl-C.
`--fixture=UID` picks a fixture, `--all VALUE` sends every channel at
one level, `--full-frame` sends all 512 slots, and `--seconds N`
releases after a while.

To read the fixture while it is lit, see
[Read a fixture's report](/help/report/).