wifi

458 Articles

Octet Of ESP32s Lets You See WiFi Like Never Before

February 15, 2025 by 13 Comments

Most of us see the world in a very narrow band of the EM spectrum. Sure, there are people with a genetic quirk that extends the range a bit into the UV, but it’s a ROYGBIV world for most of us. Unless, of course, you have something like this ESP32 antenna array, which gives you an augmented reality view of the WiFi world.

According to [Jeija], “ESPARGOS” consists of an antenna array board and a controller board. The antenna array has eight ESP32-S2FH4 microcontrollers and eight 2.4 GHz WiFi patch antennas spaced a half-wavelength apart in two dimensions. The ESP32s extract channel state information (CSI) from each packet they receive, sending it on to the controller board where another ESP32 streams them over Ethernet while providing the clock and phase reference signals needed to make the phased array work. This gives you all the information you need to calculate where a signal is coming from and how strong it is, which is used to plot a sort of heat map to overlay on a webcam image of the same scene.

The results are pretty cool. Walking through the field of view of the array, [Jeija]’s smartphone shines like a lantern, with very little perceptible lag between the WiFi and the visible light images. He’s also able to demonstrate reflection off metallic surfaces, penetration through the wall from the next room, and even outdoor scenes where the array shows how different surfaces reflect the signal. There’s also a demonstration of using multiple arrays to determine angle and time delay of arrival of a signal to precisely locate a moving WiFi source. It’s a little like a reverse LORAN system, albeit indoors and at a much shorter wavelength.

There’s a lot in this video and the accompanying documentation to unpack. We haven’t even gotten to the really cool stuff like using machine learning to see around corners by measuring reflected WiFi signals. ESPARGOS looks like it could be a really valuable tool across a lot of domains, and a heck of a lot of fun to play with too.

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38C3: Towards An Open WiFi MAC Stack On ESP32

December 28, 2024 by 15 Comments

At the 38th Chaos Communications Congress, [Frostie314159] and [Jasper Devreker] gave us a nice update on their project to write an open-source WiFi stack for the ESP32. If you’re interested in the ESP32 or WiFi in general, they’ve also got a nice deep dive into how that all works.

On the ESP32, there’s a radio, demodulator, and a media access controller (MAC) that takes care of the lowest-level, timing-critical bits of the WiFi protocol. The firmware that drives the MAC hardware is a licensed blob, and while the API or this blob is well documented — that’s how we all write software that uses WiFi after all — it’s limited in what it lets us do. If the MAC driver firmware were more flexible, we could do a lot more with the WiFi, from AirDrop clones to custom mesh modes.

The talk starts with [Jasper] detailing how he reverse engineered a lot of Espressif’s MAC firmware. It involved Ghidra, a Faraday cage, and a lucky find of the function names in the blob. [Frostie] then got to work writing the MAC driver that he calls Ferris-on-Air. Right now, it’s limited to normal old station mode, but it’s definite proof that this line of work can bear fruit.

This is clearly work in progress — they’ve only been at this for about a year now — but we’ll be keeping our eyes on it. The promise of the ESP32, and its related family of chips, being useful as a more general purpose WiFi hacking tool is huge.

Pushing 802.11ah To The Extreme With Drones

December 1, 2024 by 20 Comments

It might come as a surprise to some that IEEE, the Institute for Electrical and Electronics Engineers, does more than send out mailers asking people to renew their memberships. In fact, they also maintain various electrical standards across a wide range of disciplines, but perhaps the one most of us interact with the most is the 802.11 standard which outlines WiFi. There have been many revisions over the years to improve throughput but the 802.11ah standard actually looks at decreasing throughput in favor of extremely increased range. Just how far you can communicate using this standard seems to depend on how many drones you have.

802.11ah, otherwise known as Wi-Fi HaLow, operates in the sub-gigahertz range which is part of why it has the capability of operating over longer distances. But [Aaron] is extending that distance even further by adding a pair of T-Halow devices, one in client mode and the other in AP (access point) mode, on a drone. The signal then hops from one laptop to a drone, then out to another drone with a similar setup, and then finally down to a second laptop. In theory this “Dragon Bridge” could allow devices to communicate as far as the drone bridge will allow, and indeed [Aaron] has plans for future revisions to include more powerful hardware which will allow even greater distances to be reached.

While there were a few bugs to work out initially, eventually he was able to get almost two kilometers of distance across six devices and two drones. Something like this might be useful for a distributed network of IoT devices that are just outside the range of a normal access point. The Dragon Bridge borrowed its name from DragonOS, a Linux distribution built by [Aaron] with a wide assortment of software-defined radio tools available out of the box. He’s even put in on the Steam Deck to test out long-distance WiFi.

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WiFi Status Indicator Keeps Eye On The Network

November 16, 2024 by 19 Comments

These days, most of us take the instant availability of a high-speed link to the Internet for granted. But despite all of the latest technology, things still occasionally go pear-shaped — meaning that blistering fiber optic connection you’ve got to the world’s collected knowledge (not to mention, memes) can still go down when you need it the most.

After suffering some connectivity issues, [Arnov Sharma] decided to put together a little box that could alert everyone in visual range to the status of the local router. It won’t fix the problem, of course, but there’s a certain value to getting timely status updates. Using a 3D printed enclosure and a couple of custom PCBs, the build is fairly comprehensive, and could certainly be pressed into more advanced usage if given the appropriate firmware. If you’ve been thinking of a Internet-connected status indicator, this is certainly a project worth copying studying closely.

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The Design Process For A Tiny Robot Brain

October 20, 2024 by 13 Comments

As things get smaller, we can fit more processing power into devices like robots to allow them to do more things or interact with their environment in new ways. If not, we can at least build them for less cost. But the design process can get exponentially more complicated when miniaturizing things. [Carl] wanted to build the smallest 9-axis robotic microcontroller with as many features as possible, and went through a number of design iterations to finally get to this extremely small robotics platform.

Although there are smaller wireless-enabled microcontrollers, [Carl] based this project around the popular ESP32 platform to allow it to be usable by a wider range of people. With that module taking up most of the top side of the PCB, he turned to the bottom to add the rest of the components for the platform. The first thing to add was a power management circuit, and after one iteration he settled on a circuit which can provide the board power from a battery or a USB cable, while also managing the battery’s charge. As for sensors, it has a light sensor and an optional 9-axis motion sensor, allowing for gesture sensing, proximity detection, and motion tracking.

Of course there were some compromises in this design to minimize the footprint, like placing the antenna near the USB-C charger and sacrificing some processing power compared to other development boards like the STM-32. But for the size and cost of components it’s hard to get so many features in such a small package. [Carl] is using it to build some pretty tiny robots so it suits his needs perfectly. In fact, it’s hard to find anything smaller that isn’t a bristlebot.

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Hacker Chris Edwards demonstrating his wireless Amiga

Retro Wi-Fi On A Dime: Amiga’s Slow Lane Connection

October 13, 2024 by 9 Comments

In a recent video, [Chris Edwards] delves into the past, showing how he turned a Commodore Amiga 3000T into a wireless-capable machine. But forget modern Wi-Fi dongles—this hack involves an old-school D-Link DWL-G810 wireless Ethernet bridge. You can see the Amiga in action in the video below.

[Chris] has a quirky approach to retrofitting. He connects an Ethernet adapter to his Amiga, bridges it to the D-Link, and sets up an open Wi-Fi network—complete with a retro 11 Mbps speed. Then again, the old wired connection was usually 10 Mbps in the old days.

To make it work, he even revived an old Apple AirPort Extreme as a supporting router since the old bridge didn’t support modern security protocols. Ultimately, the Amiga gets online wirelessly, albeit at a leisurely pace compared to today’s standards. He later demonstrates an upgraded bridge that lets him connect to his normal network.

We’ve used these wireless bridges to put oscilloscopes and similar things on wireless, but newer equipment usually requires less work even if it doesn’t already have wireless. We’ve also seen our share of strange wireless setups like this one. If you are going to put your Amgia on old-school networking, you might as well get Java running, too.

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WiFi Meets LoRa For Long Range

October 7, 2024 by 20 Comments

What do you get when you cross WiFi and LoRa? Researchers in China have been doing this, and they call the result WiLo. They claim to get reliable connections over about half a kilometer. Typical WiFi runs 40 to 60 meters, barring any Pringle’s cans or other exotic tricks.

According to [Michelle Hampson] writing in IEEE Spectrum, the researchers manipulated Wi-Fi’s OFDM multiplexing to emulate LoRa’s chirp-spreading signal. The advantage is that existing WiFi hardware can use the protocol to increase range.

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