35.3 DMX Mode (Full-Featured UARTs Only)

DMX is a protocol used in stage and show equipment. This includes lighting, fog machines, motors, etc. The protocol consists of a controller that sends out commands and a receiver, such as theater lights, that receive these commands. The DMX protocol is usually unidirectional but can be a bidirectional protocol in either Half or Full Duplex mode. An example of a Half Duplex mode is the RDM (Remote Device Management) protocol that sits on DMX512A. The controller transmits commands and the receiver receives them. There are no Error conditions or retransmit mechanisms.

DMX, or DMX512A, consists of a “universe” of 512 channels. This means that one controller can output up to 512 bytes on a single DMX link. Each piece of equipment on the line is programmed to listen to a consecutive sequence of one or more of these bytes.

For example, a fog machine connected to one of the universes may be programmed to receive one byte, starting at byte number 10, and a lighting unit may be programmed to receive four bytes starting at byte number 22.