Improving WiFi Throughput With FM Radio

November 11, 2015 by Al Williams 16 Comments

WiFi networking is one of those things that is reasonably simple to use, but has a lot of complex hidden features (dare we say, hacks) that make it work, or work better. For example, consider the Distributed Coordination Function (DCF) specified in the standard. Before a station can send, it has to listen for a certain time period. If the channel is clear, the station sends. If not, it has to delay a random amount of time before trying again. This is a form of Carrier Sense Multiple Access (CSMA) channel management.

Unfortunately, listening time is dead time when–at least potentially–there is no data transmitted on the network. DCF allows you to use various handshaking packets to do virtual carrier detection and ready/clear to send, but these are also less efficient use of bandwidth. There are other optional coordination functions available in the WiFi standard, but they all have their drawbacks.

[Aleksandar Kuzmanovic] at Northwestern University and two of his students have recently published a paper with a new way to coordinate multiple unrelated wireless networks using ubiquitous FM broadcast radio signals called WiFM. Instead of trying to synchronize to the WiFi data channel, this new scheme selects a strong FM radio station that broadcasts Radio Data Service (RDS) data (the data that populates the song titles and other information on modern radios).

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Better, Smaller WiFi Throwies

October 26, 2015 by Brian Benchoff 47 Comments

Because the world doesn’t have enough electronic junk floating around, [Victor] has improved the WiFi Throwie.

A decade ago, when strong, cheap magnets, bright LEDs, and small coin cell batteries were materials fresh to hacking, someone had a great idea: tape all these items up and throw them on bridges and overpasses. The LED throwie was born, and while we’re sure the biggest installation of LED throwies looked cool, it’s really just a small-scale environmental disaster.

Since then, the ESP8266 was created, and the world now has a tiny WiFi-enabled computer that’s the size of a postage stamp. Yes, WiFi throwies already exist, but coin cells don’t work with the ESP. This means the compact and tiny ESPs are laden down with heavy lithium cells. [Victor] had a better solution: tiny lithium batteries for quadcopters exist, so why not use those?

[Victor] ended up using a small 100mAh 3.7V Lipo battery from a tiny quadcopter for this build. 100mAh isn’t a lot, but in sleep mode, the ESP only uses about 15mAh, or about 6 hours of run time. Sending a picture takes 30 seconds at 120ma, or about 120mAh, so even with a tiny battery no bigger than the ESP itself, this diminutive web server can handle 100 connections before the battery dies.

While not recommended unless you intend to retrieve your throwable web server, it is an interesting example of the latest and cheapest technology that made a throwable webserver possible; 10 years ago, both the ESP and a battery this small would have been unthinkable.

WiFi Fob Acquaints OLED With ESP

October 16, 2015 by Mike Szczys 17 Comments

When you think of WiFi in projects it’s easy to get into the rut of assuming the goal is to add WiFi to something. This particular build actually brings WiFi awareness to you, in terms of sniffing what’s going on with the signals around you and displaying them for instant feedback.

[0miker0] is working on the project as his entry in the Square Inch Project. It’s an adapter board that has a footprint for the 2×4 pin header of an ESP8266-01 module, and hosts the components and solder pads for a 128×64 OLED display. These are becoming rather ubiquitous and it’s not hard to figure out why. They’re relatively inexpensive, low-power, high-contrast, and require very few support components. From the schematic in the GitHub Repo it looks like 5 resistors and 7 caps.

The video below shows off two firmware modes so far. The first is an AP scan that reads out some information, the second is a weather-display program. Anyone who’s worked with the ESP modules knows that they have the potential to gather all kinds of data about WiFi signals — one of our favorite demos of this is when [cnlohr] used it to create a 3d light painted map of his WiFi signal strength. Chuck a rechargeable LiPo on this thing, tweak the example code for your needs, and you have a new gadget for wardriving-nouveau.

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Triple Frequency VFO On A Bamboo Breadboard

October 13, 2015 by Al Williams 5 Comments

Historically when hams built low power (QRP) transmitters, they’d use a crystal to set the frequency. Years ago, it was common to find crystals in all sorts of radios, including scanners and handheld transceivers. Crystals are very stable and precise and it is relatively easy to make a high quality oscillator with a crystal and a few parts.

The big problem is you can’t change the frequency much without changing crystals. Making a high quality variable frequency oscillator (VFO) out of traditional components is quite a challenge. However, today you have many alternatives ranging from digital synthesis to all-in-one IC solutions that can generate stable signals in a wide range of frequencies.

[N2HTT] likes to build radio projects and he decided to take an Si5351 clock generator and turn it into a three frequency VFO for his projects. The Si5351 uses a crystal, so it is very stable. However, you can digitally convert that crystal frequency into multiple frequencies over a range of about 8kHz to 160MHz.

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Google OnHub Can Has Root

October 7, 2015 by Brandon Dunson 26 Comments

It’s always nice to get down to the root directory of a device, especially if the device in question is one that you own. It’s no huge surprise that a Google product allows access to the root directory but the OnHub requires locating the hidden “developer mode” switch which [Maximus64] has done. The Google engineers have been sneaky with this button, locating it at the bottom of a threaded screw hole. Has anyone seen this implemented on other hardware before?

There isn’t a blog post regarding this, however [Maximus64] shared a video on YouTube walking us through the steps to root and un-root Google’s OnHub, which is embedded after the break. He also states “wiki coming soon” in the description of the video, so we’ll keep eye on it for an update.

We covered the product announcement back in August and have heard a few reviews/opinions about the device but not enough to make an opinionated assumption. Rooting the device doesn’t seem to increase the OnHub’s number of LAN ports but we think it’s still worth the effort.

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Party Balloon Crosses Atlantic, Tours Europe & Phones Home

October 2, 2015 by Richard Baguley 18 Comments

For the past few months, [David VE3KCL] has been launching balloons from his Canadian home fitted with radio transmitters. Nothing unusual there: quite a few people do this, including schools, hackerspaces, and individuals. What is remarkable is how far he has gotten. His S-4 flight in August of this year crossed the Atlantic, reached France and took a tour of Germany, Denmark, Sweden, Finland and Norway before finally landing in the Norwegian Sea. That’s over 10,000 kilometers (6200 miles): not bad for a couple of party balloons strung together.

The flight payload of one of the balloon flights.

Although the distance these balloons have travelled is quite remarkable, the interesting part is how [David] is tracking the balloons. Cell phones obviously won’t work over the Atlantic, and satellite transmitters are expensive, so he used a low-cost transmitter that was programmed to broadcast using a variety of Ham radio signals. The most effective seems to be WSPRnet (the Weak Signal Propagation Network), a system used by Hams to see how far low strength signals will go. This system relies on Hams leaving their receivers on and running software that uploads the received signals to a central server.

By cleverly encoding information such as height and position into this signal, he was able to turn this worldwide network into a tracking network that would report the balloon’s position pretty much anywhere on the globe. [David] is continuing to launch balloons: his latest went up on the 24th of September and travelled over 4300km (2600 miles) before the signal was lost over the Atlantic.

Sending The Internet From An LED Lightbulb

September 27, 2015 by Richard Baguley 46 Comments

The number of things that can carry Internet traffic is always increasing. Now, you can add LED light bulbs to this list, as engineers in Disney Research have just demonstrated a system that transmits Internet traffic using an LED light bulb. This method of communication isn’t new: Visible Light Communication (VLC) has been demonstrated before by Disney and others, but this project puts it into a standard LED light bulb. This bulb has been modified to include an Atheros AR9331 SoC running OpenWRT and an Atmel ATmega328p that controls the LED elements and sensors that send and receive the data. So, the device is acting as a gateway between a WiFi network and a VLC one.

Disney’s new test system (PDF link) isn’t especially fast: it can only carry about 380 to 400 bits per second, so it won’t be streaming video anytime soon. That is definitely fast enough, though to send control data to a toy, or to send a continual stream of updated data to a device in the room, such as an ebook reader with a continually updated encyclopaedia. This being Disney, the authors coin a new phrase to end their paper: The Internet of Toys.