My local electronics store Partco overdid themselves again. Believe it or not, while most of the people in US are still waiting their Stellaris Launchpads, this small Finnish electronics outlet had several in stock. Thanks to two generous donators of $11 and $1.5 respectively, I also had the financial leverage to acquire one. :)
The board came in a decent black cardboard box with a small quickstart booklet – see Hack-a-Day hands on coverage for details on the package. Even the board itself contains the URL where you can get the software package. I proceeded to download the 1.3 GB Code Composer Studio + StellarisWare package. It took 30 minutes to download, thanks to less-than-impressive transfer speeds from TI, and another 1 hour to install.
The guys at TI were generous enough to include working quickstart / driver installation guide with the package, and for once, I was actually able to walk through it without any “oh this doesn’t work anymore” -moments. Even the three drivers required were found under Software/ICDI in the setup package. Kudos! As a result of installing CCS and StellarisWare, I now had 3.75 GB and 63 872 files of additional hacking capability on my hard drive. Gone are the days where you could fit an IDE into four floppies like my Borland Turbo C++ 3.0!
Taking it for a test drive
I first followed TI’s quickstart tutorial to the end to get some blinky LED action, and even tried out the UART example – even that worked out of the box with Putty set to COM25 and 115 200 baud rate. Next I made my own project by shamelessly following the recent HaD Getting Started guide.
Sure enough, the LEDs were now blinking just like I wanted them to – and blinding me in the process: whoever thought that you need SMD LEDs that are bright enough to leave light trails on my retina must’ve been utterly mad. I recommend either wearing sunglasses (might not be enough – seriously) or placing something near-opaque (like a piece of white paper) between yourself and the Launchpad when working with the LEDs for any longer periods.
However, I couldn’t yet find much information about input side, so after some searching, I located the documentaion for StellarisWare peripheral drivel library, SW-DRL-UG-9453.pdf and started reading. Armed with that and the short “Stellaris LM4F120 LaunchPad Evaluation Board User Manual” that was found from Documentation/Board/EK-LM4F120-UM.pdf I quickly wrapped up something that was supposed to turn red and green LEDs ON when pressing user switches SW1 and SW2, respectively:
After a few busy weeks, I’ve finally arranged enough time to cover the details behind my color composite video decoding project I featured recently. Before you proceed, I suggest you read the previous post, as well as the one before that covers B/W decoding (this post builds on that one), and watch the video, if you haven’t already:
So, feel ready to learn about composite color coding, quadrature amplitude modulation (QAM)? Let’s get started! Before you get going, you can grab the example excel file so you can view the diagrams below in full size, and study the data and formulas yourself.
Combining luminance and color information
If we look at one line of video information (“scanline”), it’s basically a function of two things: luminance (brightness) and chrominance (color) information, combined to a single waveform/signal like this one I showed in my first article.
If we’d like to just have a black-and-white image, encoding it would be easy: Maximum voltage for white, minimum voltage for black, and the values between would simply be shades of grey. However, if we’d like to add color information to this signal, we need to get clever. What the engineers in the 1960’s did to get two things stuffed into one signal was to add color in sine wave modulated form on top of the luminance signal. With proper analog electronics, these two signals could then be separated from the receiving end.
I’ve been quite busy the last two weekends, first on a weekend holiday trip to Tallinn, Estonia, and then playing in the Helsinki Casual go tournament which successfully took most of my time last weekend. This has somewhat delayed my continuation to the composite video decoder project.
However, I haven’t been resting on my laurels completely even electronics-wise. My trip to Tallinn had one good by-product, namely new Audiotechnica ATH-M50 headphones. They are a marked improvement over my previous HD-500 Sennheisers, and got me inspired to getting a headphone amp, a tube-based Little Dot mkIII to be more exact. The 32 ohm ATHs don’t necessarily need an amp, but now I’ll at least be prepared if I ever end up getting something like HD-650s.
While researching for a proper USB DAC I came across an amazingaudio blog by NwAvGuy. Compared to a lot of “audiophile” coverage he seems to have a solid engineering perspective to audio issues, and he has put an amazing effort to long articles that deal with many issues that surround headphone amp gear.
In addition to great scientific info, NwAvGuy has also designed a USB DAC called ODAC, which I ordered from Head’n’Hifi (they conveniently ship inside EU so no customs). And while I was at it, I couldn’t resist getting a DIY version of NwAvGuy’s O2 headphone amplifier. Read on for my experiences on building it and pitting it against the Little Dot mkIII tube amp.
I recently finished an improved version of the NTSC composite video decoder previously featured here at Code and Life. With the bigger buffer of Picoscope 3206B, I was able to capture enough samples per frame to add color. A Youtube demonstration video has just finished uploading and you can view it below.
I already talk a bit about the techniques used in the new version, as well as the new features. For the readers of this blog, I’m planning a more detailed technical explanation, which I’ll put up as soon as I get the infographics for that one done.
Enjoy the show! If you want to take a look at the sources (or better yet, have a 3000 series Picoscope at hand), you can grab the source package. My code is licensed under GPL, see README.txt inside the archive for details.
In case anyone missed it the first time around, there are codeandlife.com ATtiny2313 breadboard headers still available for donations that exceed $10 ($10.01, $15, etc.) to the blog. If you want one, please send me an e-mail (jokkebk at codeandlife.com) with your postal address after donating, and I’ll ship one of these cuties to you as a small thanks!
All proceeds from the PayPal donations will go towards acquiring new interesting stuff to write about in this blog, so if you like the content, please consider donating!
As if I didn’t have enough things on my “to try when I have the time” list already, I recently did a little shopping in both Adafruit and SparkFun. Both had several nifty breakout boards available that promised to speed up and streamline my breadboard projects a lot. In addition to some SMD breakouts that are still in their sealed bags, here’s what I got:
I had a lot of fun soldering the breadboard headers to these little guys. Many are for future projects, like the frequency generator which I’m planning to use for some RFID experiments, and some are just to avoid stripping apart stuff like the connector breakouts. As today’s main topic, I’m covering the DS1307 realtime clock (RTC) breakout in more detail. If you are interested in some of the other items, drop me a comment and I’ll get back to it!
DS1307 Realtime Clock
A realtime clock is simply something that keeps record of the time. Usually, these types of clocks are paired with a small coin cell battery that enables them to keep on counting even if the rest of the circuit is powered of. Such is the case with this breakout, too. Adafruit has an excellent tutorial covering the assembly of this device, all you need is some solder and an iron.
After getting it together, it took me a while to get it working. I used Bus Pirate to communicate with the chip, with the following connections:
