Microplex (MPX) Project by Infidigm

xlr connector

This project will allow you to build an interface from your PC to Microplex dimmer boxes. The Microplex (MPX) project is a collection of the interface and supporting software. The primary purpose was to link lighting control to sound and music. It is recommended that you have a Microplex based lighting control system or knowledge of it before reading the following articles.


This device and all information contained on this website is for educational purposes only. This device must be used in conjunction with any and all local, provincial and federal laws. It is up to the end user to comply with all legal guidelines, thus we are not and will not be held responsible for any misuse of this product or any damages that it may cause.

Microplex Protocol Specification (As best we know)

mpx protocol diagram The Microplex protocol is a proprietary analog multiplexing lighting control protocol used primarily by NSI (Leviton). It is sent across standard XLR (Microphone) cable. Three wires are used which are +12v, GND and Signal. From our examination the Microplex protocol can handle up to 100 channels. However, the more channels, the slower the refresh rate.

The Microplex signal line swings from +8v to -6v. This was learned by examining the signal on a scope. The actual specification could be different. +8v is Fully ON and 0v is Fully OFF. Negative voltage, -6v, is a sync pulse.

The protocol starts off by sending a 5ms sync pulse. This sync pulse resets the channel counter in the dimmer boxes to zero. After the pulse, the level for the first light is send for 0.25ms. If the light is to be off, then the level will be zero volts. Next a 0.25ms sync pulse is sent. This increments the channel counters on the dimmer boxes. The 0.25ms pulses are repeated until all the channels have been sent. The process begins again with the 5ms sync pulse.

The frame time (time from one 5ms sync pulse to the next) can be calculated with the formula t = 5ms + (2x * 0.25ms) where x is the number of channels and t is in milliseconds.

RS-232 to Microplex Interface

The RS-232 to Microplex Interface allows the PC to control Microplex devices.

Interface Details


A collection of utilities for testing the RS-232 interface

Beat detection and Colour Organ are to come!