Forever.fm: Infinite Beat-matched Music

November 17, 2012 by Eric Evenchick 15 Comments

Forever.fm is [Peter]’s combination of SoundCloud and The Echo Nest that plays a continuous stream of beat-matched music. The result is a web radio station that just keeps playing.

[Peter] provided a great write up on how he built the app. The server side is Python, using the Tornado web server and Tornadio2 + Socket.IO for handling live updates in the client. To deal with the challenge of streaming audio, he wrote a LAME interface for Python that handles encoding the raw, beat-matched audio into MP3 blocks. These blocks are queued up and sent out to the client by the web server.

Another challenge was choosing songs. Forever.fm takes the “hottest” songs from SoundCloud and creates a graph. Then it finds the shortest path to traverse the entire graph: a Travelling Salesman Problem. The solution used by Forever.fm finds an iterative approximation, then uses that to make a list of tracks. Of course, the resulting music is going to be whatever’s hot on SoundCloud. This may, or may not, match your personal tastes.

There’s a lot of neat stuff here, and [Peter] has open-sourced the code on his github if you’re interested in checking out the details.

Python Script Lets You Monitor Multiple Serial Devices At Once

November 16, 2012 by Mike Szczys 17 Comments

Not knowing what’s going on inside of your electronics projects can make it quite difficult to get the bugs out. [John] was bumping up against this problem when working on wireless communications between several devices. At just about the same time his friend came up with a script with lets you monitor multiple serial devices in one terminal window.

We’re used to using minicom, a Linux package that does the job when working with serial connections of all kinds. But [John] is right, we’re pretty sure you can only connect to one device per minicom instance. But [Jim’s] Python serial terminal (available in this git repository) allows you to specify multiple devices as command line arguments. You can even use wildcards to monitor every USB connection. The script then automatically chooses a different color for each device.

The image above is from [John’s] wireless project. Even without any other background this shows how easy it is to debug this way rather than tab back and forth between windows which gets confusing very quickly.

An Extemely Unique Weather Display

November 15, 2012 by Jeremy Cook 69 Comments

Most home weather displays use an LED screen or other moderately interesting methods of showing you what’s going on outside. The [Tempescope], however, takes an entirely different route, actually recreating a tiny weather environment on your bookshelf!

This active weather device is controlled via an Arduino as well as a pump, ultrasound diffuser, and other assorted components connected to a computer. It was originally meant to display, or more accurately recreate (precreate?) tomorrow’s weather. What is even more interesting is that using [World Weather] software, it’s able to simulate the weather on any place on earth.

Early in this article [Ken] lists the art of [bonsai] as one of his inspirations. He’s open to suggestions as to how to expand this device, which can be seen after the break. We (I at least) would think it was awesome if there was actually a bonsai tree in the environment in keeping with its influences. Certainly our readers can give him some feedback as well! Continue reading “An Extemely Unique Weather Display” →

.NET For The STM32 F4 Discovery Board

October 23, 2012 by Mike Szczys 29 Comments

Here’s a technique that will let you use the .NET framework on an STM32 Discovery board. [Singular Engineer] was happy to learn that the .NET Micro Framework had been ported for STM32 chips. It’s doesn’t look like the port has hit a stable version yet, but these instructions will be enough to get you up and running. This lets you use managed code in the C# language to program an embedded device: the STM32 F4 Discovery board.

After flashing a new bootloader to the board a driver needs to be added for Windows to communicate with it. Above you can see that the board will enumerate as ‘STM32 .Net Test’. Once the driver is installed the rest of the firmware can be loaded on the board using a GUI supplied with the NETMF for STM32 package. That takes care of prepping the hardware, the rest is a painless process of configuring Visual Studio to use the board as a target. The ‘Hello World’ application then uses C# to blink an LED.

Face Tracking With An Android Device

October 15, 2012 by Mike Szczys 7 Comments

This Android device can recognize faces and move to keep them in frame. It’s a proof of concept that uses commonly available parts and software packages.

The original motivation for the project was [Dan O’s] inclination to give the OpenCV software a try. OpenCV is an Open Source Computer Vision package that takes on the brunt of the job when it comes to discerning meaning from images. To give the phone the power to move he designed and printed his own mounting brackets for the phone and a couple of hobby servos. An IOIO board connects to the Android device in order to control the motors. On the software side all [Dan] needed to do was write some code to interface the output of the OpenCV face tracking modules with the input of the IOIO. See the finished project demonstration after the jump.

This system can easily be implemented with other hardware, like this Arduino-based version we looked at earlier in the year.

Continue reading “Face Tracking With An Android Device” →

Emulators 101: How To Write A Program That Functions Like An NES CPU

October 12, 2012 by Mike Szczys 27 Comments

We’d bet everyone reading this article has played a game on an emulator at some time or another. And you may have a base idea of how those emulators work. But we’d wager the vast majority of you are clueless about the actual implementation of game emulators (we know we are). But that has all changed after seeing this demonstration of how [Bisqwit] wrote his own NES emulator. The description doesn’t cover anything more than the basics of writing code that emulates the NES CPU hardware itself. But it’s presented in such a way that makes it quite easy to understand for anyone who has a basic knowledge of programming. He starts with a switch statement for handling the processor’s opcodes and then moves through piece by piece showing how he refined his code to make it work while keeping it readable. We think this is a great teaching method and appreciate the time he put into producing this tutorial.

The explanation starts about 4:22 into the video which is embedded after the break. You’ll also find the first two demo videos there. Those involve mostly fast-motion text editing of the emulator coding process with some gameplay tests at the end of the second video.

Continue reading “Emulators 101: How To Write A Program That Functions Like An NES CPU” →

Hackaday-proofing Your Hackerspace’s Server

October 6, 2012 by Brian Benchoff 24 Comments

Last month we posted a tutorial from Hub City Labs on making your own PCBs at home. At the time, Hub City was hosting their hackerspace web site on a tiny vps graciously provided by a member. As you might expect, the throngs of Hackaday readers turned Hub City Labs’ server into a pile of molten slag and made their admin’s hair a little more gray. Their web site is up again, and Hub City provided a tutorial on protecting your server from the ravages of being Slashdotted, Farked, Reddited, and even Hackaday’d.

The solution for the first few hours was to transfer Hub City Labs’ site to an Amazon EC2 instance. Since then, they’ve moved over to a Debian EC2 instance that is able to handle half a million pageviews an hour for a WordPress site.

This amazing capability required a good bit of optimizations. A WordPress installation is set to run cron tasks on every page load; not good if you’re going to see thousands of hits every minute. The guys added define(‘DISABLE_WP_CRON’, true) to their wp-config.php file and set all the background tasks – checking to see if a page should be updated – to a fixed schedule every minute or so. Along with an increase in the WordPress cache, these optimizations increased the number of pageviews an hour from 1500 to 60000.

To get up to half a million pageviews an hour, the EC2 instance was loaded up with Varnish, a front-end cache that really speeds things up.

The result – 375 million pageviews for $15 a month – is more than Hub City Labs will probably ever need. The nature of hackerspace web sites, though – light load until Hackaday, Slashdot, or Reddit figure out you did something cool – means hosting on an expandable EC2 instance is probably the way to go.