Overview of DMX512-interface

Technical reveiw of DMX512

DMX512 has a clock frequency at 250kHz, which gives a puls width at 4ms. The DMX512 packages are delivered as a serial balanced signal as shown below (click on the picture to enlage).

In order to send a correct DMX package you must have certain stages:

1. Break
2. Mark after Break
3. Start bit
4. Data
5. End bits
6. Mark Between frames (optional)

Following is a complete stage diagram for a given DMX package(click on the picture to enlage).

The fist frame (channel 0) must have 0 as data value according to the DMX512 documentation. However some manufacturer of 'intelligent lighting' uses this first frame for remotely configuring of their lamp. In case that the first frame data is not 0, the rest of the package should be ignored!

Most DMX controllers and devices use XLR to link DMX in between the devices. The following picture describes the pin connection of a 5 pin XLR connector (click on the picture to enlage):

This was a very fast reading of how DMX works. A more detailed description will be composed - eventually.