Pixel Strips with an ENTTEC Octo - Addressing Guide

[SimpleDMX]

This guide explains how to add Pixel Strips in SDC so they line up correctly with an ENTTEC Octo (or any multi-port DMX-to-pixel controller).

The one thing to understand
A pixel controller like the Octo has separate output ports, and each port is its own independent stream that starts at its own universe.
Pixels flow freely across universes inside one port (Port 1 runs universe 1 to 2 to 3 to 4 as one continuous run).
That flow stops at the port. Port 2 does not continue from Port 1 - it starts over at its own universe (e.g. universe 5, channel 1).
So you can never let one strip's data spill from Port 1 into Port 2. Each port is a clean, separate block.

How channels fill a universe (RGB)
A DMX universe has 512 channels. An RGB pixel uses 3 channels, and a pixel is never split across a universe boundary, so each universe holds:
170 RGB pixels = 510 channels used, channels 511-512 left empty.
(RGBW uses 4 channels/pixel, so 128 pixels per universe, all 512 used.)

A standard 5m RGB strip at 60 pixels/m holds 300 pixels, so a 300-pixel RGB strip uses 2 universes:
Universe N: pixels 1-170 (channels 1-510)
Universe N+1: pixels 171-300 (channels 1-390)

Example setup
Strips: 300 pixels, RGB, WS2815
Octo, one unit, two ports:
Port 1: universes 1-4, up to 680 pixels
Port 2: universes 5-8, up to 680 pixels
Two 300px strips per port = 600 pixels (fits under 680).
One Octo (2 ports) drives 4 strips. For 8 strips you need a second Octo (universes 9-16).

Method A - add strips per port (recommended, simplest)

Add strips one port at a time.
In SDC's Add Fixtures screen, set Fixture Type to Pixel Strip and fill in the strip details (Pixel Count 300, Color Mode RGB, Segments as needed). Then for each port, set DMX Universe to that port's first universe and Starting address to 1, and click Add fixtures. SDC packs that port's strips tight, with no gaps, and the next port starts fresh.

Do this once per port:
On Port 1, add 2 strips starting at universe 1, address 1.
On Port 2, add 2 strips starting at universe 5, address 1.

This gives you the following strips:
Strip 1 starts at universe 1, channel 1 (Port 1).
Strip 2 starts at universe 2, channel 391 (Port 1).
Strip 3 starts at universe 5, channel 1 (Port 2).
Strip 4 starts at universe 6, channel 391 (Port 2).

And the Octo stays on clean defaults:
Output 1 starts at universe 1, channel 1 (Mapped Pixels 600).
Output 2 starts at universe 5, channel 1 (Mapped Pixels 600).
Do not add all the strips in one go - that makes one long run that crosses the port boundary, and the strips will not line up with the ports.

Method B - add all at once, then set the Octo start address

Alternatively, add all the strips in one go (in the Add Fixtures screen set Fixture Type to Pixel Strip, Fixtures Number 4, DMX Universe 1, Starting address 1), then tell the Octo where each port should start reading, using 1st Uni. and DMX Start Address on the Octo's Pixel Mapping page.

Added together, the strips land here:
Strip 1 starts at universe 1, channel 1.
Strip 2 starts at universe 2, channel 391.
Strip 3 starts at universe 4, channel 271.
Strip 4 starts at universe 6, channel 151.

So you configure the Octo like this:
Output 1 starts at universe 1, channel 1 (Mapped Pixels 600).
Output 2 starts at universe 4, channel 271 (Mapped Pixels 600).
Output 2 picks up exactly where strip 3 begins (universe 4, channel 271).

This packs universes with zero gaps, but Output 2 starts on an "odd" address and universe 4 is shared by both outputs (Output 1 reads its low channels, Output 2 the high ones).

Which method to use

Method A keeps the Octo on clean numbers and is harder to get wrong - preferred.
Method B wastes no universe space, but needs careful Octo start-address settings.
Either way the rule is the same: a port's pixel data must start cleanly at that port's first channel - never let one strip straddle two ports.

Quick troubleshooting

Only part of a strip responds to color/dimmer: the strip's data is straddling a port boundary - the far part is being read by a different port. Re-add per port (Method A) or fix the Octo start address (Method B).
Only the first few universes light up with many strips: the strips were added all at once and packed past the port boundaries. Add per port instead.