Just a quick one today, folks. Start to finish this should take ya 20 minutes, assuming 15 of them is trying to figure out where the hell your Sparkfun board is.
This is a wiring diagram for connecting the Sparkfun FT232RL Breakout Board (see our other posts on this device) to an SN75176 RS-488 bus transceiver. This simple combination gives you a homebrew USB DMX interface with just a couple of wires and a $0.69 logic chip from TI. It’s self-contained and USB powered – no muss, no fuss. You can buy the transciever chip and also a female XLR connector ($2.25!) from Jameco - these guys don’t suck, and they send cool catalogs. Plus, they once stayed open late so we could run up and pick up some desperately needed microcontrollers from will call for a grueling all-nighter project. Awesome.
So about 3 bucks worth of miscellaneous parts plus the Sparkfun board and a breadboard will get you up and running.
Sure, this topic has been covered plenty of other times – even so far as to provide beautiful PCB layouts for FT232 DMX adapters. But a lot of readers don’t have access to nice SMT soldering stations and don’t want to mess with placing the FT232RL themselves. And plus, it’s another excuse to get the Sparkfun FT232RL Breakout board. You can breadboard it into a DMX interface for your next basement rave, and then go back to interfacing your TI-85 calculator when you’re done.
The wiring is dead simple. Tie DE (Data out enable) to +5V, tie !RE (Receive enable) to GND, connect TxD and RxD, and attach an XLR connector. We had fine results with using CAT-5 cable as our DMX cable – the run was only about 15 feet but it worked fine with no glitches. We used one twisted pair for the DMX + and – signals, and a single wire from another twisted pair for the GND (COM) connection. We’ve included a current-limiting resistor in ours, but you can probably get away without it assuming you don’t have terrible ground loop issues in your setup. Remember that this device is powered from the raw USB +5V, and not from the 3.3V regulator on the FTDI chip. So connect it where we show, sucka!
Fig 1 – Sparkfun Board as DMX Interface
We’re assuming you’ve already installed the FTDI drivers to make it look like a virtual com port. If not, go get em from FTDI.
The last thing you’ll need to do in order to actually use this beast to control your lights, is to download FreeStyler, a great freeware DMX controller. Plug in your newly wired interface and then fire up Freestyler.
Assuming nothing has caught fire so far: In the Freestyler setup, choose Enttec Open DMX. At that point, it will find the device and begin blinking out TxD’s. You are now up and running and ready to sequence some killer light shows.
Cheers!
Total newbie here, but want to give this a go.
Don’t have the components yet, but I am ordering them.
I understand the diagram above, but what how do I “Tie DE (Data out enable) to +5V, tie !RE (Receive enable) to GND, connect TxD and RxD, and attach an XLR connector.”
Am I soldering them? or using wires/connectors etc?
As I said, am noob, but keen!
Any help will be great!
Tie just means to connect. Ours was on a breadboard, so it was just a matter of plugging in wires between the correct pins. For example, the DE pin will have a wire connecting it to the +5V supply.. You can certainly solder the wires if you want to, that would work just fine.
Gotcha, that makes sense! many thanks.
time to buy a bread board!
(yes, that is how n00bish I am)
No problem, you’re very welcome. This is a good project to start with because the wiring is not very difficult. Just remember that if it gets hot when you plug it in, you should unplug it quickly. Probably + and – supplies are reversed. Good luck!
Hi,
Two questions,
Does it matter which transceiver is used? RS422, RS485, RS488?
Wouldn’t this one work also? http://www.sparkfun.com/products/9822
Looks like outofthebox USB->DMX
but I have no clue.
Thx! Eo
No, it needs to be 488. But good of you to check, it was worth a shot.
I will try my luck with the USB->RS485 converter
And Iam thinking of forging a SN75176 into an XLR Plug with this ftdi cable:
http://www.sparkfun.com/products/9718 on the other end.
Thank you for the ideas and the fast answer!
hello, can I make this circuit connecting a 5v 1A external source, because I bought a converter cable usb to serial RS232 ready, and not think in the VCC and GND outputs RS232 connector
Yes, you can connect the TI chip to 5V 1A source as long as your RS232 cable gives 0-5V output. If RS232 cable is 0-3.3V, it could be a problem – SN75176 cannot understand 0-3.3V if VCC=5V.
Remember, you must connect GND of SN75176 to GND of RS232! Even the shield is OK, but GND must be connected!