code, circuits, & construction

ITP just got some nifty flat panel mounts that can rotate 360 degrees. They’re very easy to move, it takes only one hand. When I saw them, I thought, “what good is a rotating mount if the content on the screen can’t rotate too?” So I came up with a little system to sense the screen’s rotation. Here’s how to turn those screens into a very big iPhone. Thanks to Michael Dory for his help in coding this and Dan O’Sullivan for the final clue.

The screens have a mac mini mounted on the back to display digital content. I added an Arduino with an accelerometer mounted on it to sense the angle of the screen’s rotation, then sent that data into Processing.  This example doesn’t do much, but the code can be re-used for any Processing application that needs to know the screen’s rotation.

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Kimio Kosaka has made a way to program a virgin Atmega168 without a hardware programmer.  You use a modified version of the avrdude programming software that can access the extra pins of an FTDI USB-to-serial chip, do a little soldering on your Diecimila, and Bob’s your uncle, as the Italians say.

This question comes up all the time in physical computing classes and workshops. Recently Zach Eveland posted a good informal but thorough answer to the ITP physical computing list. This isn’t an authoritative medical answer by any means, but it’s good enough to keep you safe if you follow his recommendations.

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Microcontroller Shop has a variety of useful electronic and microcontroller parts. What they have that’s exciting are the XBee boards from droids.it. They sell the XBee Simple board, the XBee Serial board, and the XBee USB board.

Control Geek - John Huntington’s guide to all things in show control. John’s book on show control covers every show control data protocol you might need and then some.

ITP alum David Bamford has posted some Illustrator symbols for making circuit schematics, for those people comfortable in Illustrator. Thanks to David for the link and the symbols.

Technorati Tags: electronics

Droids.it has a breakout board for XBee radios, and a USB-to-Xbee board available.

The USB board is nice, because in addition to having a built-in 5V-to-3.3V regulator and indicator LEDs, it’s got all the pins of the XBee broken out on the side of the board. Makes development of XBee projects easier.

The breakout board also has its own regulator on board, making it easy to interface with a 5V project. It’s also got the serial pins broken out to a single row, making it easy to mount on the side of a breadboard.

The prices on both are reasonable for the European market. As the US dollar continues to sink, they’re a bit pricier for US customers, but still reasonable, for now.

Thanks to Rob Faludi and Jeff LeBlanc for testing help, and to Luigi Carnevale for supplying sample boards.

Technorati Tags: electronics, networked objects, networks

When you’re making a microcontroller circuit that drives a high current load like a motor or an incandescent light, it’s not uncommon to make a mistake and create a circuit that draws too much electrical energy on startup and causes the microcontroller to reset itself constantly. To debug this, it helps to put a routine in your startup() function so you can see when the microcontroller has started up. For example, I often blink an LED three times in the startup. If the LED blinks three times then stops, I know the microcontroller has successfully run the startup and gone into its main loop. If it blinks constantly, I know the microcontroller is continually resetting, so there’s a problem.

Hans Steiner recently showed me his trick for checking for the startup routine on the Arduino: he writes to the microcontroller’s EEPROM, or permanent memory, and reads back the result. Every time the Arduino resets, it’ll increment the EEPROM value. Since this value is stored even when the Arduino is not powered, you’re going to get a new number each time it’s run.

Thanks to Hans for the code.

Technorati Tags: pcomp, physical computing

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Mike Kuniavsky and Tod Kurt of ThingM recommended these RFID readers from Son Micro. They’re some of the cheapest ones I;ve seen on the market, and relatively small.

Thanks to Anne Hong for sending the link.

Technorati Tags: electronics, networked objects, networks, RFID

Recently, I’d been trying to re-program some Atmega168’s for use in Arduino modules, and was having no luck using my AVRISP MkII programmer. All appeared to be working, but it kept failing. I even dug into the details of avrdude, and the programmer responded as if it was working but delivered no love.

Fortunately I had on hand a USBTinyISP from Adafruit. Even more fortunately, Limor Fried has written some nice instructions on the programmer and on installing and running avrdude to program with it. What’s nice is that she’s packaged the software well, so you can run it without too much hassle. The only thing I had to learn was how to point avrdude at her custom config file, by using the -C flag, like so:

./avrdude -C avrdude.conf -v -p m168 -e

(etc)

Even nicer, David Mellis is including support for this programmer in Arduino 0010, so that I can burn new bootloader firmware onto the chips using it without needing to touch the command line app.

Even nicer still: her programmer’s cheaper than the AVRISP mkII (of which I have blown up a few). I may blow this one up in time too, but I’ll be able to afford to replace it much easier.

Technorati Tags: atmel, electronics