Tuesday, November 14, 2006

Phidgets: the Beginning

So, I'm a total hardware n00b. I've written software for a decade, and happy talking about inheritence, encapsulation, polymorphism and tossing around newer buzzwords like dependency injection and all that.

But I decided to start a hardware project. I'm not going to give away the ending, mostly because I'll probably never get there. Remind me to tell you the story about the coffee table I was going to make once.

Anyway, I bought an 8/8/8 Interface Kit from Phidgets.com. It's a smallish thing, about the size of a deck of cards, and about a hundred bucks delivered. It's designed to pass inputs and outputs through USB to a computer, where software running there actually makes the decision about what to do when. Plus, one of the hojillion languages they support is Java, so that feels right at home.

I've got the thing on my desk now, and am installing the software. Except it needs the .net framework, blah blah blah. It's nice enough to redirect me to the download page, and after getting confused about my 64 bit proc but 32 bit operating system I'm good. That done, their software installs fine. While .Net was .downloading I got eclipse set up with their Java examples, and once the software was installed and the device connected their InterfaceKit example ran right out of the box. Granted, I have nothing hooked up to it, so I don't know if it's doing anything, but it prints lots of stuff to the screen. I grabbed a wire and jammed it between the ground and the different inputs, and successfully made stuff print to the screen. Cool!

Next up is outputs. For that I have an LED that I clipped off of a defunct printer screen. I'd have desoldered it, but Nicole just bought the desoldering iron, and I wanted her to be the first to use it. I hook it up, and nothing happens. So I hit their website, which has the "n00b manual for InterfaceKit", which is six pages long. I've read manuals that are 20 pages and have less useful information. There happens to be a section on "hooking up LEDs to your InterfaceKit", and by section I mean a page. It mentions anodes and cathodes. Which I look up on wikipedia, turn my LED around and it works.

Sort of. I've written my own software to turn input #1 on for 2 seconds, then off. The LED responds by shining bright and steady in the "on" state, but instead of being off for the "off" state, it flashes. I vaguely remember that "digital" outputs have some kind of square wave mojo going on below a certain hobgoblin threshhold or something, but all that information is eleven years old, and there is a lot of beer and parties standing between my CE 101 class and today's attempt. I also suspect that the answer is actually on the LED page of the manual, but again too much inebriation between those symbols and the present day.

So, I've got a flashing LED. The software has been fairly straightforward to this point, and while they don't release the sourcecode to their Java libraries, they do have a reasonably well written Javadoc. Moreover, to this point things are written in a pretty straightforward manner. To turn the LED on and off, I've written these lines:


(with sleep statements in between)

So, I'm reasonably sure I haven't screwed that up. I even have system.out.printlns in between, which of course make me feel dirty, but I'm ignoring that for now.

I'm not the only hardware n00b connected to the global inter-tubes, so I sign up for their forums. I could complain about the way the forums insist on mailing me a generated password as though I'm going to be doing stock trading on this thing or something, but that's really just sniping at this point. I shut up about the password thing, and enter "flashing LED" into the forums.

No luck there, I think now that the problem has to do with the shoddy wire I'm using (cut out of an old phone cable, stripped with a kitchen knife, and not a solid wire but twisted copper). I changed the LED to another output, and this time off was off, but on was flashing. I went to change it again, and dropped the LED off the end of the wire (I just had it wrapped, not soldered or anything), and have decided to declare that to be the problem, and call it a night.

Next time: wire strippers and real wire!

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