Wireless Hacks

1050 Articles

PIC Mesh, Accessible Distributed Networking

December 17, 2016 by 6 Comments

Wireless networks have been reduced to a component, for most of us. We fit a device, maybe an ESP8266 module or similar, and as if by magic a network exists. The underlying technology has been abstracted into the firmware of the device, and we never encounter it directly. This is no bad thing, because using wireless communication without having to worry about its mechanics gives us the freedom to get on with the rest of our work.

It is however interesting once in a while to take a look at the operation of a real wireless network, and [Alex Wong], [Brian Clark], and [Raghava Kumar] have given us a project with the opportunity to do just that. Their PIC Mesh university project is a distributed wireless mesh network using 2.4GHz NRF24L01 transceiver modules and PIC32 microcontrollers. They have it configured for demonstration purposes with a home automation system at the application layer, however it could be applied to many other applications.

The real value in this project is in its comprehensive but easy to read write-up of the kind you’d expect from a university project. The front page linked above has an overview of how the mesh works, but there are also pages taking us through the hardware, the networking software layer, and the home automation application layer. If you have ever wanted to understand a simple mesh networking system, this is a good place to start.

We’ve covered quite a few mesh networks over the years, but sadly we can only link you to a few of them. We’ve had a mesh network using the Raspberry Pi, Project Byzantium’s “ad-hoc wireless mesh networking for the zombie apocalypse“, and a 1000-node Xbee network for testing purposes.

Bluetooth Turns 5

December 12, 2016 by 23 Comments

Last week, the latest and greatest member of the Bluetooth family of wireless specifications was announced to the world: Bluetooth 5! What main changes are in store? Read the FAQ (PDF), or dig into the full spec (bigger PDF) at 2,800 pages.

Their big-print selling points include “up to 4x the range, 2x the speed, and 8x the broadcasting message capacity” to power the Internet of Things. Etcetera. [Akiba] pointed out via Twitter that they get the fourfold increase in range by adding an extra zero to the “Maximum Output Power” spec, going from 10 mW maximum power to 100 mW. That would do it.

In less snarky news, they’re also allowing for a lower-bitrate mode that will also increase range without simply boosting the power. The spec is actually being changed to let the user work out their optimal blend of power, range, and bitrate. We’re down with that. But you’re not getting 4x the range and 2x the speed without paying the bandwidth piper. That’s just physics.

If you use the beacon mode in Bluetooth Low Energy (BLE), you’ll be happy to hear that they’re lengthening the beacon packet from 31 bytes to 255, so you can send a bunch more data without consuming too much power. That’s the “8x”. Bluetooth 5.0 is also backwards compatible with Bluetooth 4.2, so you don’t have to redo anything if you don’t want to take advantage of the newer features. Your current BLE beacons will keep working.

Finally, there’s some contention-detection and other bandwidth optimizing going on, which is welcome in our crowded 2.4 GHz office spectrum. Our guess is that’s where the “2x speed” is largely coming from, but there are about 2,750 pages that we haven’t read yet, so if you’re digging into the spec, let us know what you find in the comments.

Thanks to [Akiba] for tipping us off to this via Twitter. Go check out his great talk on getting hacker stuff in Shenzhen that was presented at the SuperCon.

Mexican Highschoolers Launch 30 High Altitude Balloons

December 5, 2016 by 15 Comments

No matter whether you call them “picosatellites” or “high altitude balloons” or “spaceblimps”, launching your own electronics package into the air, collecting some high-altitude photos and data, and then picking the thing back up is a lot of fun. It’s also educational and inspirational. We’re guessing that 264 students from 30 high schools in Aguascalientes Mexico have new background screens on their laptops today thanks to the CatSat program (translated here by robots, and there’s also a video to check out below).

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Creepy Wireless Stalking Made Easy

December 4, 2016 by 55 Comments

In a slight twist on the august pursuit of warwalking, [Mehdi] took a Raspberry Pi armed with a GPS, WiFi, and a Bluetooth sniffer around Bordeaux with him for six months and logged all the data he could find. The result isn’t entirely surprising, but it’s still a little bit creepy.

If your WiFi sends out probe requests for its home access points, [Mehdi] logged it. If your Bluetooth devices leak information about what they are, [Mehdi] logged it. In the end, he got nearly 30,000 WiFis logged, including 120,000 probes. Each reading is timestamped and geolocated, and [Mehdi] presents a few of the results from querying the resulting database.

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Repurpose A Classroom Clicker For Great Justice

December 4, 2016 by 42 Comments

If you’ve been in a university class of a certain size, with a professor who wants to get live feedback from the students, you’ve probably been forced to buy a Turning Point “clicker”. Aside from the ridiculousness of making students pay for their professor’s instructional aides (do the make you pay extra for the chalk too?!?!) these clickers are a gauntlet thrown down to any right-minded hacker because they supposedly contain secrets.

[Nick] had one of these gadgets, and hopped right up on the shoulders of giants to turn it into a remote control that interfaces with his computer and drives a synthesizer, so he can work through the chord changes by clicking. His two references, to [Travis Goodspeed]’s nRF promiscuity hack and to [Taylor Killian]’s Arduino library for the clickers are a testament to why we need both reverse engineers doing the hard work and people who’ll wrap up the hard work in an easy-to-use library.

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Start Your Path To Becoming An Antenna Guru

November 27, 2016 by 15 Comments

We’ve known a few people over the years that have some secret insight into antennas. To most of us, though, it is somewhat of a black art (which explains all the quasi-science antennas made out of improbable elements you can find on the web). There was a time when only the hams and the RF nerds cared about antennas, but these days wireless is everywhere: cell phones, WiFi, Bluetooth, and even RF remote controls all live and die based on their antennas.

You can find a lot of high-powered math discussions about antennas full of Maxwell’s equations, spherical integration and other high-power calculus, and lots of arcane diagrams. [Mark Hughes] recently posted a two-part introduction to antennas that has less math and more animated images, which is fine with us (when you are done with the first part, check out part two). He’s also included a video which you can find below.

The first part is fairly simple with a discussion of history and electromagnetics. However, it also talks about superposition, reflection, and standing wave ratio. Part two, though, goes into radiation patterns and gain. Overall, it is a great gateway to a relatively arcane art.

We’ve talked about Smith charts before, which are probably the next logical step for the apprentice antenna wizard. We also covered PCB antenna design.

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ZX81 Connects To The Network

November 23, 2016 by 32 Comments

 

[Victor Trucco] makes us wish we spoke Portuguese. He’s done a lot of retrocomputing projects including connecting a ZX81 to the Internet to load programs. The project uses — what else — an ESP8266 to get the WiFi communications. You can see a video below if you want to exercise your high school Portuguese.

It is somewhat ironic that the ZX81’s CPU is kept busy driving the video, reading the keyboard, and running about just over 3 MHz which doesn’t even translate into 3 MIPS on that processor. Meanwhile, the “servant” ESP8266 has a 32-bit Tensilica CPU running at 80 MHz. Times have changed.

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