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Kevin Johnson
Works at Georgia Institute of Technology
Attended Georgia Institute of Technology
Lives in Atlanta, GA
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Kevin Johnson

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Is this a poll?
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TI has the worst e-store ever.  It's always slow, and when they have something popular, it just straight up dies.  I want some of these!
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Success!  In for two.
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I came across a couple of these dev boards while organizing.
http://www.ti.com/tool/msp-exp430fr5739
I picked up two of them when they were on sale for $15 (and free shipping!) and just now considered how awesome they are, especially when compared to Arduino boards (for clarity, I use Arduinos as dev boards and program in C/assembly. AVRs are awesome but the Arduino IDE is horrible.).

The uC is a 16-bit processor with an internal oscillator up to 24MHz (controllable from software). Interestingly, it uses 16kB of non-volatile FRAM for shared program memory and RAM, meaning that you'll probably have much more RAM available than the 2k on an ATMEGA328.

The board has two push-buttons and eight LEDs for UI and a 2-axis accelerometer and a thermistor already on there. There are pads for a 32.768kHz crystal if you want to do RTC stuff. And it has the hardware on there for programming (so no external programmer needed) and USB-UART.

So color me impressed (especially for $15). Now to come up with something to use them for...
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Yeah, a matrix with an overlay with an array for the words that can be changed should be awesome :-)
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I find it ironic that the androidcentral.com site lets you log in with Facebook or Twitter but not Google.
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Creating an App Inventor app begins in your browser, where you design how the app will look. Then, like fitting together puzzle pieces, you set your app's behavior. All the while, through a live c...
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Yeah, It'll stretch well, and we can staple gun it?? The paper work well now, but it's so fragile.
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View the source.
 
Javascript FTW (view source!)
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File recovery win. I opened a file today that I was working on last week and found that it had somehow reverted to a very old version. My guess is that I accidentally had it open in two places and when I closed everything on Friday, saved over my changes with an old version.

It contained some very tedious work that I definitely didn't want to figure out again, so I downloaded a raw data hard drive viewer and searched for a word that I knew would be fairly unique to that file. Just happened that the first hit, after a couple seconds, was my lost file, and I was able to copy all the necessary information.

The extremely useful program: http://www.theabsolute.net/sware/dskinv.html
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I'm guessing about 2 more years for 3D printers to reach mainstream price point. Already down to $500.
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YES.
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While organizing toys I came across a 16x24 LED display that I bought years ago off ebay but never tried to use. A little reading of a datasheet and a little programming of a microcontroller and it worked first try. How often does that happen?

Frickin' never (minus one, apparently).
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Woohoo I'm famous!
"Thanks, Google," wrote K Johnson, "8143575 is just as easy to remember as KJohnson." Michael found this on a label on a box of cat litter. "This product gets Lighter when shi...
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Compilers sure throws some tricky wrenches in your code sometimes.

I thought I was being smart by declaring all applicable functions as static to allow more compiler optimization. But suddenly, one of my interrupt service routines started taking longer than it was allowed to. I did some simulation, and the ISR overhead was on the order of 120 cycles (almost twice what I would expect). I looked at the disassembly and saw that the ISR was pushing something like fourteen registers to the stack and popping them back off at the end. Why on earth...?

The ISR runs a couple hundred times in quick succession and then, on the final iteration, disables itself. After disabling the interrupt, I figured it would be safe to call a few functions since there would be plenty of time before the interrupt needed to be enabled again. But since those functions were static and only called in that one place, the compiler inlined them. All of a sudden, my ISR contained much more code than I had planned for, using many more registers than I had planned for, and thus had to push and pop all those registers to the stack to preserve state.

I'm not sure what the moral of the story is, but it's probably "don't call functions from ISRs".
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In English: WTF?
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Have him in circles
87 people
DreamSourceLab's profile photo
Porsche Bridges's profile photo
Kevin Braswell's profile photo
Paul Johnson's profile photo
Natalia Valdes's profile photo
Andrew Lunsford's profile photo
Kavi Vu's profile photo
matt rogge's profile photo
Tom Collins's profile photo
Work
Occupation
Electrical Engineer
Employment
  • Georgia Institute of Technology
    Lecturer, present
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Currently
Atlanta, GA
Previously
Atlanta, GA - Park Falls, WI - Hancock, MI - Proscott, AZ - Morocco - South Africa - Hexham, England
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Story
Tagline
Electrical Engineering win.
Introduction
Georgia Tech.  Electrical Engineering.  Long hair.
Education
  • Georgia Institute of Technology
    Electrical Engineering
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Male
Other names
Bones
Apps with Google+ Sign-in
Neat..
Public - 7 months ago
reviewed 7 months ago
3 reviews
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