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E68X-to-DMX Adapter

The E68X-to-DMX Adapter as the name implies, converts the TTL logic level of the DMX Raw data stream from the E68x controller and converts it to the proper RS-485 levels. The E68x can be configured to send a raw DMX data stream to the first pixel controller connector in a group. The output is a single-ended TTL level (5v) which is not suitable for direct connection to a DMX RS-485 network. This adapter takes that input and converts it to the proper differential output required. This initial version is a simple design and does not emply any isolation at the input or outputs to the RS-485 line. This was done to keep costs to a minimum and keep the board small. Later versions may include full isolation if there's enough demand for it.


The schematic is quite simple and contains few parts. It can be made quite cheaply by replacing certain jumpers, etc with wires. The output jumper layout to support both Renard or DMX wiring schemes was taken from member RPM's E1.31-Renard/DMX bridge. Setting all of the jumpers one way uses the pseudo standard RJ45 DMX format with D+/D- on 1/2 and ground on 7. Setting all the jumpers the other way selects Renard format with D+/D- on 4/5 and ground on 1/2. Note that in both cases, it is still DMX output - this just saves you from making a special cable so that straight Cat5 patch cables can be used. The board includes an optional 78L05 voltage regulator that can be used if you exclusively use 12v pixels. This will convert the voltage to 5v for the RS485 chip but can be bypassed if you have 5v pixels.
E68XTODMX Schematic

Bill of Materials

The ST485BN/CN is no longer carried by Mouser but all of the parts can be found at Digi-Key instead.

Part Description Qty Store Part Number
ST485CN - RS485 Transceiver 1 Digi-Key 497-6729-5-ND
L78L05ABZ - 5v Regulator 1 Digi-Key 497-1009-ND
1751264 - 4P 3.5mm TB 1 Digi-Key 277-5744-ND
120 ohm Resistor 1 Digi-Key CF14JT120RCT-ND
SA105E104MAR - .1uF Capacitor 3 Digi-Key 478-3156-1-ND
1-390261-2 - 8-pin socket 1 Digi-Key A100204-ND
68000-203HLF - 1x3 pin header 4 Digi-Key 609-3464-ND
5555164-1 - RJ45 jack 1 Digi-Key A31442-ND
2-382811-1 - Shunt 4 Digi-Key A31697-ND

Note that none of the parts are critical - you can substitute similar parts. In addition, the 78L05 regulator and two of the .1uF capacitors are only needed when using 12v pixel power - if using 5v, you can simply jumper out the regulator (shown on PCB). A top-entry jack can be substituted for the RJ45 jack.

Board Layout

The board layout is very straight forward with a pixel connector and reguator (optional) at one end, an RS-485 chip in the middle and an output jumper setup with RJ45 to DMX connector at the end. Two methods of connections to the E68x are possible. The first consists of a standard 4-contact terminal block that can be wired back to the removable block that plugs into the E68x. The other method consists of running a 20 gauge or so wires down from the board and terminating them directly into a removable block that can be plugged directly into the E68x. This latter method saves on the terminal block and keeps the setup quite neat. Only 3 wires are used (+5v, Ground, Data) but a 4-wire connector was used so it would physically match up to the connector (1.5mm pitch) on the E68x.
E68X-DMX Schematic


Install the 120 ohm resistor - there is no polarity
Install a wire jumper instead of the 7805 regulator if you are using 5v pixel power - do NOT install if using 12v pixel power
Install the three 100nF decoupling capacitors - there is no polarity
Install the 8-pin DIP Socket
Install the two 2x3 headers horizontally
Install the four shunts - all four on left for DMX or all four on right for Renard output wiring
If you are not using the 4-pin terminal block, take four pieces of wire and bend the ends over as shown
Insert the wires and solder them in
Here are the four wires shown from the bottom
Trim the four wires to about 1/2" or so
Insert the four wires into the Terminal Block provided from your E681
Install the RJ45 connector
Completed E68XTODMX Adaptor (5v version)
If you are using 12V Pixel power, install the 7805 regulator
If you are using the 4-pin terminal block, install it now
Install the RJ45 connector

E68x Configuration

The E68x should be configured with the following parameters:

  • Pixel Type of "DMX PIXEL" - use the command CH X,5 where X is the Group number
  • String Count of 1 - use the command ST X,1 where X is the Group number
  • Pixel Count of 170 - use the command PI X,170 where X is the Group number

The converter must be plugged into the first connector of the group (1-1, 2-1, 3-1 or 4-1) if you want a full universe (actually 510 channels).

You can also get creative and configure it with 4 strings of up to 42 pixels and use all four connectors in a group and you will end up with four separate DMX streams starting at addresses of 1-126, 127-252, 253-378 and 379-504. Smaller string lengths will result in smaller bundles of DMX addresses. Note that all strings sizes have to be the same length for a given group. Also remember the unit of measurement is pixels or 3-channels - not single channels.

Converter Configuration

The four jumpers must be placed all on the left for DMX wiring or all on the right for Renard wiring. You must install all four of the jumpers or install wire jumpers instead for the converter to work properly.

If you are using 5v pixel power on the connector you can jumper out the 78L05 regulator to provide 5v power. If you are using 12v pixel power then be sure to NOT have the bypass jumper installed or it will fry the RS485 chip. It is not recommended to use this board with 24v pixels as it may cause the regulator to overheat.


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