Picture Frame That Scrapes Train Times From The Web

January 8, 2013 by Mike Szczys 22 Comments

rpi-train-times-fixture

Whenever [Gareth James] needs to catch a train he has only to push a button on this frame and the next three departure times will be displayed. As you can see from the post-processing in the photo, this is accomplished by a Raspberry Pi board using a few familiar tools.

Let’s take a look at the hardware first. He acquired a 7″ LCD display which he removed from its plastic case. The bare screen will easily fit inside of the rather deep wood frame and its composite video input makes it quite simple to interface with the RPi board. There was a little work to be done for power. The LCD needs 12V so he’s using a 12V wall wart to feed the frame, and including a USB car charger to power the RPi. The last thing he added is a button connected to the GPIO header to tell the system to fetch a new set of times.

A Python script monitors the button and uses Beautiful Soup to scrape the train info off of a website. To get the look he wanted [Gareth] wrote a GUI using tkinter. Don’t miss the demo after the jump.

If you need a bit of a primer on scraping web data take a look at this guide.

Continue reading “Picture Frame That Scrapes Train Times From The Web” →

PyMCU Test Project Looks Like A Minecraft Mob

December 20, 2012 by Mike Szczys 5 Comments

pymcu-controlled-blockhead

Hackaday’s own [Jeremy Cook] has been testing out the pyMCU board and managed to put together an animated block head that looks like it could be a foe in Minecraft. That’s thanks mostly to the block of foam he’s using as a diffuser. The face of the project is a set of LEDs. These, along with the servo motors that move the neck are controlled using Python code which you can glance at after the break (there’s a video demo there too).

We first saw pyMCU early in the year. The PIC 16F1939 offers plenty of IO and acts as a USB connected bridge between your hardware and your Python scripts. Speaking of hardware, the test platform used to be an RC helicopter. [Jeremy] scrapped most of it, but kept the servo motors responsible for the pitch of the rotors. The board makes these connections easy, and the concept makes controlling them even easier. In fact, there’s only about 17 lines of code for the functions that control the servos. The rest is a simple UI built with Tkinter.

Continue reading “PyMCU Test Project Looks Like A Minecraft Mob” →

Python Can Be Your Best Friend When It Comes To Binary Math

December 13, 2012 by Mike Szczys 20 Comments

$python-binary-math$

If you’re into microcontrollers you know the ability to think and perform math in binary is a must. [Joe Ptiz] has been looking for a way to keep from being distract by the math when coding while still keeping the binary strings in the forefront of his mind. The solution he came up with is to use the Python interpreter as a binary math aide.

We knew that you could use Python to convert between decimal, hexadecimal, and binary. But we failed to make the leap to using it for troubleshooting bit-wise operations. We can see this being especially useful when working with sixteen-bit I/O ports like those found on STM32 chips. For us it’s easy to do 8-bit math in our head, but doubling that is another story.

The image above is one screenshot from [Joe’s] tutorial. This illustrates a few different bit-wise operators given decimal inputs but displaying binary as output. He also illustrates how you can use python to test out equations from C code by first setting the variables, pasting the equation, then printing the result to see if the output is what was expected.

Web Scraping Tutorial

December 10, 2012 by Mike Szczys 36 Comments

Web scraping is the act of programmatically harvesting data from a webpage. It consists of finding a way to format the URLs to pages containing useful information, and then parsing the DOM tree to get at the data. It’s a bit finicky, but our experience is that this is easier than it sounds. That’s especially true if you take some of the tips from this web scraping tutorial.

It is more of an intermediate tutorial as it doesn’t feature any code. But if you can bring yourself up to speed on using BeautifulSoup and Python the rest is not hard to implement by trial and error. [Hartley Brody] discusses investigating how the GET requests are formed on your webpage of choice. Once that URL syntax has been figured out just look through the source code for tags (css or otherwise) that can be used as hooks to get at your target data.

So what can this be used for? A lot of things. We’d suggest reading the Reddit comments as there are several real world uses discussed there. But one that immediately pops to mind is the picture harvesting [Mark Zuckerburg] used when he created Facemash.

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.

LED Fun And Light Painting With The PyMCU

November 5, 2012 by Jeremy Cook 2 Comments

Recently [Richard] at [pyMCU] was nice enough to send me one of their units to try out. As featured here before, this little board allows you to control physical things using your computer and the Python programming language. After evaluating it and making a LED blink, there were a couple other LED projects I wanted to try.

The first idea was to make a LED chaser. This was quite simple, using a little code and plugging in a few LEDs. From this, since you can make the LEDs chase each other, then in the right sequence it should be able to be used to display images using long-exposure photography. Be sure to check out the video after the break of this 10 LED chaser/light bar being assembled.

The results of this LED light bar experiment were really cool, writing some simple text and image with 10 LEDs. Considering the low component count, this is one of the simplest light bar builds that we’ve seen. Programming was simple as well, since the computer using Python does all the processing of the drawing as well as physically turning the LEDs on and off. Of course this setup isn’t without its limitations, having to be connected to a computer being the most obvious. Continue reading “LED Fun And Light Painting With The PyMCU” →