ws2801 light pixels straight from computer? Please advise.

[mnlagrasta]

Software guy here, flailing with hardware. Sorry if it's a dumb question.

I want to run one of the ws2801 based light strips, direct from a mac mini without an arduino (or other microcontroller). Is it possible to do this with a usb ftdi cable like sold in adafruit's store? If so, would that fall under the "bitbang" technique?

The other option, if I think I can figure it out, would be to use a BeagleBone and use, I think, the GPIO pins to send the signals down the led strip.

In both cases the BeagleBone or Mac mini is just acting as a web server to receive remote commands and call a script that manipulates the lights. The beagle board option would be cool because it would appear to not be tethered to a computer even though it technically would be still.

If you are really curious, I am trying to ramp up a project before exhibiting at Maker Faire and I'm thinking about moving away from the ThingM parts. http://makerfaire.com/pub/e/7403

Wait...is it ok to post links here?

Anyway, any help is GREATLY appreciated!

Mike

[adafruit_support_bill]

The FTDI approach would not work. A Beaglebone would - but you would have to locate or write a library for it. We have existing libraries & demo code that run on any of the Arduino boards. The Arduino Ethernet board is capable of acting as a web-server.

[pburgess]

Hey Mike,

Unfortunately, no, FTDI bitbang mode doesn't work well with the ws2801 pixels (really, I put a TON of futile effort in trying to make the combination work).

Even if it did work, enabling FTDI bitbang mode on the Mac is a bit annoying. Why the allergy to Arduino? Aside from being close to plug-and-play, the low-level LED code is already written.

Hey, if you're using BlinkMs, this might be worth exploring: http://www.paintyourdragon.com/?p=43
I've controlled BlinkMs via the monitor port on an iMac in the past (there's even some code at the above link), but it's been ages and I can't say whether this will compile and run on the current OS X, nor if it's compatible with the graphics hardware in your Mac Mini. What version of both do you have?

[mnlagrasta]

Thanks for the responses. Certainly no allergy to Arduino, it is my preferred microcontroller. I was just trying to keep this project as accessible as possible to the less technical crowd. Right now it's just some node code, the linkm and however many blinkms one wishes to buy. And if you keep that to less than 8 blinkms, you don't even need to supply power.

Now I'm doing sort of an advanced version that will support more lights and is a little cheaper. I would rather make use of the addressable strands from adafruit, giving me 20 leds for the price of 3 blinkms.

I suppose an arduino + ethernet or wifly shield would be pretty slick too. Then I could completely decouple the computer and hit it by ip instead of the server running on the computer itself.

Thanks again for the clarification!

[paulstoffregen]

It's possible to make a Teensy programmed with Arduino act pretty much the same as the FTDI bitbang mode, at the same full USB speed, but without any messy driver issues. To your software, it's just a normal serial port. Like the bitbang mode, there are some special considerations on formatting the data.

It's explained in this thread.

viewtopic.php?f=47&t=25854