MIDI / DMX512 Interface


MIDI / DMX512 Interface

This is a do-it-yourself construction manual for an interface to control a DMX512 lighting bus by MIDI channel messages. A similar project operating with RS-232 and ASCII text is described on this website too.

The hardware may be assembled optoisolated or not. As a special feature the MIDI interface can be configured as a standard RS-232 interface with 115200 Baud. This way it can be operated at higher speed together with a LAN or Wifi to RS-232 converter.
The command set is almost compatible with the discontinued MIDI / DMX512 Generator made by Cinetix.

A detailled construction- and operation manual is provided here (PDF file).

MIDI/DMX-Interface
Basic assembly of the MIDI / DMX512 Interface in "Eurobox" enclosure. Not optoisolated

The most essential features of MIDI control:

  • In contrast to proprietary control equipment the MIDI / DMX interface can be operated with any kind of software which is capable to transmit (and optionally receive) MIDI channel messages.

  • Any DMX channel 1 to 512 can be set to any level with 8 bit resolution by sending a single NOTE ON message (sets even DMX level) or a single POLY KEY PRESSURE message (sets odd DMX level). Alternatively this is done by pair of CONTROL CHANGE messages (using only 1 MIDI channel).

  • Hue, saturation and luminance for RGB LED lamps can be set with simple CONTROL CHANGE messages. The commands are organized for easy operation of a bar with up to 5 RGB lamps.

  • For any DMX channel a fade transition can be executed automatically, duration programmable up to 31.9 seconds. This diminuishes the expense for design of complex lighting sequences considerably. Any number of fade processes can be active simultaneously on all DMX channels.

  • The flexibly configurable chaser feature loads sequences of presets (=lighting scenes) automatically in a cyclic manner to DMX OUT. Softly faded transitions are possible. The flash feature pushes all DMX channels to a defined level for a short period of time.

  • The lighting scene of the MIDI / DMX interface can be saved permanently as a preset. Up to 227 presets can be stored and reloaded at any time. Together with presets no. 0 to 3 the system configuration is stored, too
    The transition from the previous lighting scene is performed softly with the actual fade time.
    During power-on or by a MIDI RESET message preset no.0 is loaded automatically.

  • One MIDI message can poll the levels of 1 to 128 consecutive DMX channels of the recently transmitted DMX packet via MIDI OUT.

Hardware essentials

The layout of the PCB is held simple with a single wire layer and is strictly arranged in a 2.54 mm grid. The printed "wires" are put in a way which is reproducable for manual construction on a hole matrix veroboard (german: Lochrasterplatine) with round copper pads (not stripes).
  • The PCB design fits into 3 easily available cabinet models:a low cost plastic standalone ("Eurobox" from Reichelt and Conrad 52 31 32) a rugged aluminium ("Fischer Elektronik FRAME" PCB  size  100x75mm) and (though less used for MIDI applications) a DIN rail compatible ("Camdenboss CNMB/4 PCB size 86.5*68mm"),.

  • The heart of the circuit is a microcontroller ATmega1284P clocked at 12 MHz. The 40pin DIL case demands no special skills for manual assembly.

  • An Atmel compatible programming connector is provided on the PCB. After programming a jumper may be placed here to filter messages on specific MIDI channels.

  • The actual lighting scene is buffered internally. It is permanently transmitted at the DMX bus until it is modified by another command. Interruption of the MIDI connection has no influence on the DMX bus pattern. After power cycling automatically preset no.0 is loaded.

Downloads:
The subsequently downloadable material is copyrighted (c)2014-15 by Cinetix GmbH.
Assembly and use of the interface is permitted for free by everybody for any purpose ("freeware")
All information is based on best knowledge, but without any warranty. Any responsibility is excluded.

PCB layout (1:1 TIF format), may be assembled optoisolated or no t

Firmware hex code for ATmega1284P (Version 1.4 , 25/09/2014)
(recommended Fuses configuration: extended 0xFC, high 0xCD, low 0xF7)

Detailled construction- and operation manual (PDF file).


* State of information January 2015.
* Right of technical modifications reserved. Provided 'as is' - without any warranty. Any responsibility is excluded.
* This description is for information only, without any warranty. No product specifications are assured in juridical sense.
* Trademarks and product names cited in this text are property of their respective owners.