Real-Time Bluetooth for DMX-512 Communication

DMX-512 is a protocol is developed as an industrial standard for controlling light units. These units could be projectors, moving head scanners (see Figure 1), strobos etc. As the name implies, the protocol supports 512 channels on each line (one unit may take up more channels).

The Martin MAC250+. Two of these scanners are available for system tests.
Figure 1.The Martin MAC250+. Two of these scanners are available for system tests.
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The DMX-512 protocol sends 512 bytes to each unit, connected by a bus wire. Each unit is configured to receive a specific byte. For example, the value in byte 200 (also called channel 200), tells projector number 6 to set the intensity to the value of this byte. The principle of the data stream is shown in Figure 2 below.

The DMX-512 protocol.
Figure 2. The DMX-512 protocol.
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This project focuses on the possibility of applying the Bluetooth wireless technology instead of a wired solution. Using Bluetooth has two major advantages. First of all it is wireless, which means that the cabling for the DMX-512 signal may be left out. A large number of PDAs have Bluetooth, hence the light technician may use a PDA to control a lamp when mounting. Using self-configuring pico-nets (Bluetooth only supports seven slaves, hence pico-nets are used to inter-connect groups of eight) the configuration of the network can be completely automated. However, the cost is signal re-transmission, due to the limited range of Bluetooth. The feasibility study of the performance of Bluetooth for DMX-512 transimission has been investigated by previous groups, and the results show that this can be done even with Bluetooth 1.1 and the performance would of course improve with Bluetooth 1.2.

A setup with multiple Bluetooth hops and two light units in each end of a chain could be the testbed for the analysis. The project work will focus on the design and implementation of the proposed solutions, along with an analysis of the performance of Bluetooth 1.1 and 1.2 as real-time communication channels. The implementation of connection initialization, pico-net formations, re-transmissions and protocol for DMX-512 signal transmission is the goal of the project.

The areas in this project will be:

  • Investigation of the DMX-512 protocol.
  • Investigation of network algorithms for inter-connected pico-nets.
  • Design of protocol for real-time DMX-512 signal transmission over Bluetooth pico-nets.
  • Analysis of real-time properties of large scale wireless solutions (Blueotth 1.1 and 1.2).
  • Implementation of Bluetooth HW/SW for transmitting between DMX units and control from PC.

Proposal by
Dan Bhanderi - Spam protected. Please type in manually.