Annax ETH2 / ETH4
The Annax ETH2 and ETH4 are monochrome LED matrix display units intended for passenger information applications in rail and bus vehicles. They are controlled entirely over Ethernet — no serial or IBIS bus connection is involved.
The ETH2 and ETH4 belong to the same product family and are driven by identical software (the pixelman application). They differ in physical form factor and panel size; the protocol they speak is the same across both variants.
Communication
The units connect via a standard Ethernet port and accept commands over two transports:
- UDP — stateless, fire-and-forget; suitable for simple one-shot commands
- TCP port 1976 — session-based (SSTDM protocol); the device registers with a server and maintains a persistent connection to receive commands
In a typical installation the unit acts as a client: on boot it reaches out to a configured server address on port 1976 and registers itself. The server then pushes display commands to it.
Display content
Content is described using AnnaxXML, an XML-based command language. A display update involves three steps:
- Define a page — specify one or more fields (rectangular regions) with their position, size, font, and text alignment
- Set content — provide the text or bitmap to render in each field
- Activate the page — tell the unit to switch to that page
The display is purely monochrome (pixels are either on or off). Text supports several font sizes and can be configured to scroll horizontally when the content is too wide to fit. Multiple pages can be stored and switched between.
Other commands allow controlling brightness, turning the display on or off, querying device status, and triggering built-in test patterns.
Notes
- The manufacturer's original server software is no longer available. An open-source compatible SSTDM server and command-line client have been developed through protocol reverse-engineering and are available at the Annax ETH2 project.
- A common panel configuration encountered in the field is 150 × 36 pixels.