The DMX IO Platform Module is a 4-channel DMX transceiver. In receive mode it can control up to four channels of low-current TTL (3.3v, e.g., for servos and small LEDs) or high-current (12v, e.g., lamps, relays, solenoids, stepper motor, etc.) output. In transmit mode, it can issue commands to an entire DMX universe (512 channels).

Dual XLR-3 connectors allow the module to act as a receiver or transmitter (master) node in a DMX network and A 9-position DIP switch allows for address configuration without changing firmware.

The RS-485 hardware design allows for software switching between RX and TX modes allowing advanced programmers to experiment DMX receiver projects as well as serial- to-DMX applications.

What is DMX?

DMX is a serial protocol that runs over a RS-485 hardware link. It was originally designed to control lights (Chauvet has a bunch of cool DMX lights), but it is also used to control servos, LED's, stepper motors, relays, and other devices (Like a DMX Skeleton). It's an easy-to-use, robust protocol that allows for 1,500 Feet + cable runs using inexpensive cable.

A DMX network has 1 master device, and 1 or more slave devices. 512 control channels are available and many slave devices use more than one channel (e.g., a light might use 1 channel for pan, another for tilt). Each channel can support 256 possible values, although some slave devices will combine 2 channels for 65,535 possible values. Channel values can be changed about 44 times per second, or 44Hz.

About This Module

You can add the DMX IO Module to the Propeller Platform, a protoboard, or even a breadboard. I'll talk about using it with a Parallax Propeller or Arduino at the end of this instructable.

The DMX IO module was designed by Jon Williams and is licensed under the MIT License. He reviewed DMX (and this module) in his November Nuts n' Volts column, which you can read here (pdf).

You can download the design file or buy the kit or a bare PCB from Gadget Gangster. Pre-assembled modules are also available.

Build time is about 45 minutes. Warm up your soldering iron and go to the next step!

Step 1: Using: Usage Ideas

While your iron is warming up, here are a few examples of the cool things you can do with DMX;

Christmas Display

There are a number of DMX dimmer/switch packs (here's one) that let you plug in a lamp or a strand of christmas lights (or anything else that can plug into the wall), turn it on or off, pulse, or dim it. The DMX IO module can issue commands through DMX to dimmer/switch packs or other DMX devices; stuff like Fog Machines, lasers, bubbles, or a snow machine.

Do A Light Show

Color your house

W Hotel In Boston

The DMX IO module can send commands to hundreds of slave devices, like these COLORdash Quad wash lights.

Control Servos and Animatronics

The DMX IO module can also be used to receive commands to control servos, pneumatics, or nearly any device you can think of - you get 12V from the screw-down terminals, and the board also has headers for 3V devices.

Just a few fun things that can be done. Next, we'll start building the module, and at the end of this instructable, there's info on how to program it (don't worry, it's pretty easy).

Step 2: Make: Parts List

Let's make sure you have the following parts. You can also grab these parts from mouser - each part on the schematic has mouser part # (the file format is ExpressPCB)

Parts List

DMX IO PCB
9 position 300 mil DIP switch
3mm Green LED
4x TIP 125 Transistors
2x 200uF Electrolytic Capacitors
1x .1uF Radial Ceramic Capacitor
2x Shunt Jumpers
8 Pin DIP Socket
56 Pin Headers
4x 2N3904 Transistors
4x 2 Position Terminal Blocks
RS485 / RS422 Transceiver IC
10 Pin Bussed Resistor Network (10k ohm)
XLR3 Male Connector
XLR3 Female Connector
3x 4.7k ohm Resistor (Yellow - Violet - Red)
4x 470 ohm Resistor (Yellow - Violet - Brown)
4x 1k ohm Resistor (Brown - Black - Red)
1x 330 ohm Resistor (Orange - Orange - Brown)
1x 120 ohm Resistor (Brown - Red - Brown)

Step 3: Make: Resistors

Add the first three resistors, 4.7k ohm (Yellow - Violet - Red) at R2, R3, and R4.

Step 4: Make: 120 Ohm Resistor

The 120 ohm Resistor (Brown - Red - Brown) goes at R1

Step 5: Make: 470 Ohm Resistors

R5, R6, R7, and R8 are 470 ohms (Yellow - Violet - Brown)

Step 6: Make: 1k Ohm Resistors

Right next to the 470 ohm Resistors goes the 1k ohm Resistors (Brown - Black - Red)

Step 7: Make: 330 Ohm Resistor

This should be your last discrete resistor, and it's used to limit the current to the LED. It's 330 ohms (Orange - Orange - Brown) and goes at R13

Step 8: Make: LED

Let's add the green LED, it goes right in the middle of the board, as indicated in the photo. Note that the shorter lead goes through the square hole.

This led is connected to P27. All you need to do to turn it on is bring P27 high.

Step 9: Make: Ceramic Capacitor

Add the ceramic Capacitor to the board, as indicated on the photo. This capacitor is not polarized, so it doesn't matter which lead goes in which hole.

Step 10: Make: 2N3904 Transistors

Add the 2n3904 Transistors as indicated in the photo. Note that the flat side of the transistor lines up with the flat side as indicated on the board.

Step 11: Make: Screw Down Terminals, Prep

There are 4 Screw Down Terminals, each has a small groove in one side and small bevel in the other. We're going to connect all of the terminals into a single 'stick'. First, identify the bevel on each of the terminals.

Step 12: Make: Screw Down Terminals, Connecting

Now, slide them together. You can see in the photo how the terminals slide together, from the bottom.

Step 13: Make: Screw Down Terminals, Complete

Slide all four of the terminals together, as shown in the photo. You'll have a single terminal 'stick'.

Step 14: Make: Solder Down Terminal

Add your newly created terminal stick to the board. Note that the 'clamps' (where you insert the wire you want to connect with the terminals) should be closer to the edge of the board.

Notice the boxes marked 'W' to the right of the transistors? Those are pin headers for controlling servos. The pin next to the W is the control signal, the middle pin is connected to +5V, and the pin on the right is connected to ground. If you want to use the DMX IO to control low power devices, add 3 pin headers at each location.

Step 15: Make: IC Socket

The IC socket goes at U1 with the notch closer to the ceramic capacitor.

The notch position doesn't actually matter for the socket (It will work either way), but it will help to make sure you put the IC in the correct direction, so it's better to do it correctly.

Step 16: Make: DIP Switch

The 9 position DIP switch goes at SW1. Each switch on the DIP is marked with a number (right below the switch), and the switch labeled '1' goes to the left, as indicated on the photo.

Step 17: Make: Bussed Resistor, Identifying Pin 1

The bussed resistor has a 'pin 1', it's identified by looking at the body of the component - pin 1 is marked by an arrow.

Step 18: Make: Bussed Resistor, Adding to Board

Pin 1 goes through the square hole that's also marked on the silkscreen, as indicated in the picture.

Step 19: Make: Jumpers

There are two jumpers on the board,

TERM: If the DMX IO module is an end node (transmit or receive), slide the jumper shunt to connect these 2 pins.

GND: If the DMX IO module is the master (transmitting) - only one node will use this jumper. If so, you just slide the jumper shunt to connect these 2 pins.

If the module is the master transmitter, you'll jumper shunt both jumpers.
If the module is the last receiver, you'll jumper shunt the TERM jumper only.
Otherwise, you don't need to jumper shunt either jumper.

If your pin headers comes in a big strip, cut 2 pins out with your dikes and add to the board where it's labeled 'TERM'. Cut out 2 more pins and add at 'GND'.

Step 20: Make: Electrolytic Caps

The 2 electrolytic caps (they look like little metal cans) go at the places indicated in the photo. The electrolytic caps are polarized - the longer pin goes through the square hole (also marked with a '+').

On the cap, there's a stripe. The shorter lead (closer to the stripe) goes through the longer lead - closer to the edge of the board.

Both caps are 220uF

Step 21: Make: TIP125 Transistors

There are 4 big TIP125 transistors, they go between the smaller transistors and the screw down terminal block. Note the tab on each transistor, it goes so the Tab is closer to the 'C' marked in the silkscreen.

Step 22: Make: XLR3 Connectors

There are 2 XLR connectors, (male and female) that go on the board. The female connector goes in the box labeled 'DMX Out' and the male connector goes in the box labeled 'DMX In'.

It's pretty easy to get these correct as the mounting holes on the board only fit the correct connector.

Step 23: Make: RS485 IC

The RS485 Transeiver IC (It's an ST ST485BN) goes in the socket. Note the notch on the IC goes on top, closer to the ceramic capacitor.

If you don't need the jumper shunts, just slide each over a single pin. This way, you won't lose them in case you eventually do need them.

Lastly, add pin connectors to the outside row of the board. These pins allow you to connect the DMX IO module to the Propeller platform, protoboard, or breadboard. On the board, each connection is labeled P0 - P31. The schematic has a list of connections (expresspcb format), but here's how they map out;

P0: DIP Switch '256'
P1: DIP Switch '128'
P2: DIP Switch ' 64'
P3: DIP Switch '32'
P4: DIP Switch '16'
P5: DIP Switch '8'
P6: DIP Switch '4'
P7: DIP Switch '2'
P8: DIP Switch '1'

P9: DMX channel 1
P10: DMX channel 2
P11: DMX channel 3
P12: DMX channel 4

P24: RX2 (Input)
P25: TXE (Transmit Enable)
P26: TX2 (Transmit)

P27: Activity LED

Step 24: Using DMX

DMX is pretty easy to use:

For Propeller

RECEIVE

Jon Williams' November Spin Zone article provides a lot of detail about the DMX and how he developed the objects. He also coded an easy-to-use object (jm_dmxin) that will simplify reading DMX values. With your spin code, you'll just need to add the library;

obj dmx : "jm_dmxin"

When you need to turn on the dmx monitoring,

pub main dmx.init(24,16) '24 = receive pin, 26 = activity LED

to get the value of the channel, it couldn't be easier;

dmx.read(chan)

With that dmx value, you can do whatever you want - display something on a TV display, flip on a light, do some pwm to a channel, etc.

When you're done reading DMX values, you can free the cog with;

dmx.finalize

Jon has done a cooler version with an RGB lighting fixture using Bit Angle Modulation in his article.

SEND

If your DMX IO module is the master transmitter, don't forget to slide on the jumper shunts to both jumpers. For software, there's a DMX send object in the Propeller Obex that makes for an easy DMX output. Here's an example of how to use it;

First add the object to the object section of your spin code;

obj dmxout : "DMXout"

to start it up;

dira[25] := outa[25] := 1 'brings the TX enable high dmxout.start(26) ' starts the dmxout

sending dmx values couldn't be easier - just;

dmxout.Write(2, 255) 'channel = 2, value =255

For Arduino

The DMX IO module has regular .1" pin spacing, so it won't fit on top of an Arduino, however, you can still connect it to the arduino with wires or a protoboard.

There's a good guide on the Arduino Playground. For connections;
P0:P8 - DIP Switches
P9 - Channel 1
P10 - Channel 2
P11 - Channel 3
P12 - Channel 4
P24 - DMX RX
P25 - Transmit Enable
P26 - DMX TX
P27 - Activity LED

That's it - Do something cool with DMX!

Introduction: 4 Channel DMX Transceiver