FRDM-K22F ARM Board Doesn’t Have An SD Card Socket? Not So Fast!

The Freescale Freedom development boards come in several different flavors and at several different price points. It is pretty clear that Freescale counts up pennies to hit their desired target price. For example, the costlier boards with bigger processors (like the K64F which costs about $35) has sockets to fit an Arduino shield or other external connections. Many of the cheaper boards (like the KL25Z for $13) just has PCB holes. If you want to add sockets, that’s on you.

The $30 K22F board has the sockets, but it also omits a few components that are on the PCB. [Erich Styger] noted that there was a micro SD card socket footprint on the board and wondered if he could add an SD card to the board by just soldering on the socket. The answer: yes!

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Code Craft: Subtle Interrupt Problems Stack Up

[Elliot Williams’] column, Embed with Elliot, just did a great series on interrupts. It came in three parts, illustrating the Good, the Bad, and the Ugly of using interrupts on embedded systems. More than a few memories floated by while reading it. Some pretty painful because debugging interrupt problems can be a nightmare.

One of the things I’ve learned to watch out for over the years is the subtlety of stack based languages, like C/C++, which can ensnare the unwary. This problem has to do with the corruption of arrays of values on a stack during interrupt handling. The fix for this problem points up another one often used by black hats to gain access to systems.

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Optical Rectenna Converts Light To DC

Using multiwall carbon nanotubes, researchers at Georgia Institute of Technology have created what they say are the first optical rectennas–antennas with rectifiers that produce DC current. The work could lead to new technology for advanced photodetectors, new ways to convert waste heat to electricity and, possibly, more efficient ways to capture solar energy.

A paper in Nature Nanotechnology describes how light striking the nanotube antennas create a charge that moves through attached rectifiers. Challenges included making the antennas small enough for optical wavelengths, and creating  diodes small enough and fast enough to work at the extremely short wavelengths. The rectifiers switch on and off at petahertz speeds (something the Institute says is a record).  Continue reading “Optical Rectenna Converts Light To DC”

ARMing A Breadboard — Everyone Should Program An ARM

I’m always a little surprised that we don’t see more ARM-based projects. Of course, we do see some, but the volume isn’t what I’d expect given that low-level ARM chips are cheap, capable, low power, and readily available. Having a 32-bit processor with lots of memory running at 40 or 50 MIPS is a game changer compared to, say, a traditional Arduino (and, yes, the Arduino Due and Zero are ARM-based, so you can still stay with Arduino, if that’s what you want).

A few things might inhibit an Arduino, AVR, or PIC user from making the leap. For one thing, most ARM chips use 3.3V I/O instead of the traditional 5V levels (there are exceptions, like the Kinetis E). There was a time when the toolchain was difficult to set up, although this is largely not a problem anymore. But perhaps the largest hurdle is that most of the chips are surface mount devices.

Of course, builders today are getting pretty used to surface mount devices and you can also get evaluation boards pretty cheaply, too. But in some situations–for example, in classrooms–it is very attractive to have a chip that is directly mountable on a common breadboard. Even if you don’t mind using a development board, you may want to use the IC directly in a final version of a project and some people still prefer working with through hole components.

The 28 Pin Solution

One solution that addresses most, if not all, of these concerns is the LPC1114FN28 processor. Unlike most other ARM processors, this one comes in a 28 pin DIP package and works great on a breadboard. It does require 3.3V, but it is 5V tolerant on digital inputs (and, of course, a 3.3V output is usually fine for driving a 5V input). The chip will work with mbed or other ARM tools and after prototyping, you can always move to a surface mount device for production, if you like. Even if you are buying just one, you should be able to find the device for under $6.

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Vintage Computer Fest: Berlin 2015

Berlin was a good city to be a geek in last weekend. Alongside the Berlin Maker Faire, there was the 2015 meeting of the Vintage Computing Festival: Berlin (VCFB). Each VCFB has a special theme, and this year it was analogue computers, but there was no lack of old computers large and small, teletext machines, vintage video game consoles, and general nerdy nostalgia.

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Controlling Guitar Amps With Servos

[fichl] plays electric guitar, and with that hobby comes an incredible amount of knob twisting and dial turning. This comes at a cost; he can’t change the settings on his small amp without taking his hands off the guitar. While larger, more expensive amps have multiple channels and footswitches, this tiny amp does not. Instead of upgrading, [fichl] came up with a device that turns his single channel amp into a completely programmable one, with just an Arduino and a handful of servos.

The amp in question – an Orange Dark Terror head – has just three knobs on the front of the chassis, volume, shape, and gain. [fichl] had the idea of controlling these knobs electronically, and the simplest solution he came up with is cheap hobby servos. These servos are mounted in an aluminum box, and mount to the knobs with a few shaft couplings.

The footswitch is the brains of the setup, with three buttons, four LEDs, and a DIN-5 output jack that delivers power, ground, and three PWM signals to the servo box. With the help of an Arduino Nano, [fichl] can change any of the knobs independently, or switch between twelve programmed settings. It’s an interesting setup, and something that could serve as a prototype for a much larger system on a much larger amp.

Halloween Hood Has Hideous LED Gaze

Looking to create fear and dread with your Halloween costume? [Becky Stern] over at Adafruit has you covered, with her tutorial on building a mystical hood with LED eyes, perfect for your next Jawa, Black Mage, or Orko costume.

This creepy-looking creation is based around a Gemma controller driving two NeoPixel Jewels, small circular RGB LED boards. The Gemma drives the boards to slowly fade on and off for the required creepy eye effect, but it would be easy to create other lighting patterns.

Speaking of patterns, the tutorial also includes a sewing pattern for the hood, and plans for a 3D printed battery holder that would make the whole thing very easy to carry. If the eyes aren’t enough, how about adding an LED magic staff to complete your creepy ensemble? Or perhaps some light-up dinosaur spiky plates?

Do you have any good Halloween costume hack plans? Let us know in the comments, and we’ll put together a list of the best closer to the hideous day.

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