linux

619 Articles

Testing The Outernet Dreamcatcher SDR

June 20, 2017 by 8 Comments

What do you get when you cross an ARM-based Linux PC and an RTL-SDR? Sounds like the start of a joke, but the answer is Outernet’s Dreamcatcher. It is a single PCB with an RTL-SDR software defined radio, an L-band LNA, and an Allwinner A13 processor with 512MB of RAM and a 1 GHz clock speed. The rtl-sdr site recently posted a good review of the $99 board.

We’ll let you read the review for yourself, but the conclusion was that despite some bugs, the board was no more expensive than pulling the parts together separately. On the other hand, if you uses, for example, a Raspberry Pi 3, you might expect more support and more performance.

Despite the L-band hardware, there is a bypass antenna jack that allows you to receive other frequencies. There’s also two SD slots, one to boot from and another for storage. Several pieces of software had trouble running on the somewhat sluggish CPU, although some software that is optimized for the particular processor used fared better. You can read the details in the review.

The board is interesting, although unless you have a special packaging problem, you are probably as well off to combine a Pi and a dongle, as we have seen so many times before. If you have more horsepower you can even make the Pi transmit, although we’d suggest some filtering if you were going to do that for real.

Btrfs For The Pi

June 18, 2017 by 19 Comments

File systems are one of those things that typical end users don’t think much about. Apparently, [seaQueue] isn’t a typical end user. He’s posted some instructions on how to run an alternate file system–btrfs–on the Raspberry Pi.

The right file system can make a big difference when it comes to performance and maintainability of any system that deals with storage. Linux, including most OSs for the Raspberry Pi, uses one of the EXT file systems. These are battle-hardened and well understood. However, there are other file systems, many of which have advanced features superior to the default file system for some applications.

Btrfs, often pronounced “butter eff ess”, begin life at Oracle and was born from an idea in an IBM paper. It offers advanced features like pooling, snapshots, and the ability to fuse multiple devices into one logical device. One notable feature the file system offers is copy-on-write. That means file copies can share common blocks as long as they stay common.  Compression is available, as is seeding a file system with read-only storage, which could be very useful in some embedded systems. You can also configure several types of RAID using nothing but btrfs. You can see a video presentation about features of btrfs below.

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JeVois Machine Vision Camera Nails Demo Mode

May 17, 2017 by 31 Comments

JeVois is a small, open-source, smart machine vision camera that was funded on Kickstarter in early 2017. I backed it because cameras that embed machine vision elements are steadily growing more capable, and JeVois boasts an impressive range of features. It runs embedded Linux and can process video at high frame rates using OpenCV algorithms. It can run standalone, or as a USB camera streaming raw or pre-processed video to a host computer for further action. In either case it can communicate to (and be controlled by) other devices via serial port.

But none of that is what really struck me about the camera when I received my unit. What really stood out was the demo mode. The team behind JeVois nailed an effective demo mode for a complex device. That didn’t happen by accident, and the results are worth sharing.

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Sudo Google Assistant

May 16, 2017 by 18 Comments

A Raspberry Pi kicking around one’s workbench is a project waiting to happen — if they remain unused long enough to be considered a ‘spare.’ If you find you’ve been pining after an Alexa or your own personal J.A.R.V.I.S., [Novaspirit Tech] might be able to help you out — provided you have a USB mic and speaker handy — with an accessible tutorial for setting up Google Assistant on your Pi.

A quick run-through on enabling a fresh API client on Google’s cloud platform, [Novaspirit] jumps over to the Raspbian console to start updating Python and a few other dependencies. Note: this is being conducted in the latest version of Raspbian, so be sure to update before you get underway with all of your sudos.

Once [Novaspirit] gets that sorted, he sets up an environment to run Google Assistant on the Pi, authenticates the process, and gets it running after offering a couple troubleshooting tips. [Novaspirit] has plans to expand on this further in the near future with some home automation implementation, but this is a great jumping-off point if you’ve been looking for a way to break into some high-tech home deliciousness — or something more stripped-down — for yourself.  Check out the video version of the tutorial after the break if you like watching videos of guys typing away at the command line.

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History Of Git

May 11, 2017 by 89 Comments

Git is one of those tools that is so simple to use, that you often don’t learn a lot of nuance to it. You wind up cloning a repository from the Internet and that’s about it. If you make changes, maybe you track them and if you are really polite you might create a pull request to give back to the project. But there’s a lot more you can do. For example, did you know that Git can track collaborative Word documents? Or manage your startup files across multiple Linux boxes?

Git belongs to a family of software products that do revision (or version) control. The idea is that you can develop software (for example) and keep track of each revision. Good systems have provisions for allowing multiple people to work on a project at one time. There is also usually some way to split a project into different parts. For example, you might split off to develop a version of the product for a different market or to try an experimental feature without breaking the normal development. In some cases, you’ll eventually bring that split back into the main line.

Although in the next installment, I’ll give you some odd uses for Git you might find useful, this post is mostly the story of how Git came to be. Open source development is known for flame wars and there’s at least a few in this tale. And in true hacker fashion, the hero of the story decides he doesn’t like the tools he’s using so… well, what would you do?

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Mangling Images With Audio Effects

April 16, 2017 by 24 Comments

Ever wonder what those snapshots you took of your trip to Paris would look like if you ran them through a Proco RAT or a Boss Overdrive? How about a BF-3 flanger? [Robert Foss] wrote in with this nifty little script (GitHub) that processes images as if they were audio files so that you can try it out without investing in a rack of analog pedals. Test your audio/visual DSP intuition and see if you can name the images without looking at the effects.

If you know your Linux command-line utilities, there’s really not much to it — scroll down to the very bottom of the script to see how it’s done. ffmpeg converts the images to YUV format, which works much better than RGB for audio processing, and then sox adds the audio effects. Another trip through ffmpeg gets you back to an image or video.

OK, it’s cheating because it’s applying the audio effects inside the computer, but nothing’s stopping you from actually taking the audio out and running it through that dusty Small Stone. Of course, once you’ve got audio outside of the computer, the world is your oyster. Relive the glorious 70’s when video artists made works using souped-up audio synthesizers. If you haven’t seen the Sandin Image Processor or the Scanimate in action, you’ve got some YouTubing to do.