Circuit Secrets: Exploring A $5 Emergency Light

December 28, 2024 by Heidi Ulrich 2 Comments

Who would’ve thought a cheap AliExpress emergency light could be packed with such crafty design choices? Found for about $5, this unit uses simple components yet achieves surprisingly sophisticated behaviors. Its self-latching feature and decisive illumination shut-off are just the beginning. A detailed analysis by [BigCliveDotCom] reveals a smart circuit that defies its humble price.

The circuit operates via a capacitive dropper, a cost-effective way to power low-current devices. What stands out, though, is its self-latching behavior. During a power failure, transistors manage to keep the LEDs illuminated until the battery voltage drops below a precise threshold, avoiding the dreaded fade-to-black. Equally clever is the automatic shut-off when the voltage dips too low, sparing the battery from a full drain.

Modifications are possible, too. For regions with 220V+ mains, swapping the dropper capacitor with a 470nF one can reduce heat dissipation. Replacing the discharge resistor (220k) with a higher value improves longevity by running cooler. What remarkable reverse engineering marvels have you come across? Share it in the comments! After all, it is fun to hack into consumer stuff. Even if it is just a software hack.

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Stream Deck Plus Reverse Engineered

December 26, 2024 by Al Williams 6 Comments

[Den Delimarsky] had a Stream Deck and wanted to be free of the proprietary software, so he reverse-engineered it. Now, he has a Stream Deck Plus, and with the same desire, he reverse-engineered it as well.

The device has eight buttons, a narrow screen, and four encoder dials. The device looks like a generic HID device to the host machine, and once it has been configured, doesn’t need any special software to function. By configuring the device using the official software in a virtual machine under the watchful eye of Wireshark, it was possible to figure out how that initial setup worked and recreate it using a different software stack.

If you’ve never done this kind of thing before, there is a lot of information about how to find USB data and draw inferences from it. The buttons send messages when pressed, of course. But they also accept a message that tells them what to display on their tiny screen. The device screen itself isn’t very big at 800×100.

[Den] packages everything up in the DeckSurf SDK, an open source project that lets you control Stream Decks. So if you just want to control the Deck, you don’t need to know all these details. But, for us, that’s where the fun is.

Way back in 2015, we covered some guy who had sniffed out a USB signal generator. That was easy since it was a serial port. However, you can go pretty far down the rabbit hole.

Unexpectedly Interesting Payphone Gives Up Its Secrets

December 11, 2024 by Dan Maloney 7 Comments

Reverse engineering a payphone doesn’t sound like a very interesting project, at least in the United States, where payphones were little more than ruggedized versions of residential phones with a coin mechanism attached. Phones in other parts of the world were far more interesting, though, as this look at the mysteries of a payphone from Israel reveals (in Hebrew; English translation here.)

This is a project [Inbar Raz] worked on quite a while ago, but only got around to writing up recently. The payphone in question was sourced from the usual surplus market channels, and appears to have been removed from service by Israeli telecommunications company Bezeq only shortly before he found it. It was in pretty good shape, and was even still locked tight, making some amateur locksmithing the first order of the day. The internals of the phone are surprisingly complex, with a motherboard that looks more like something from a PC. Date codes on the chips and through-hole construction date the device to the early- to mid-1990s.

With physical access gained, [Inbar] turned to the firmware. An Atmel flash chip seemed a good place to look, and indeed he was able to pull code off the chip. That’s where things took a turn thanks to the CPU the code was written for — the CDP1806, a later version of the more popular but still fringe CDP1802. This required [Inbar] to fall down the rabbit hole of writing a new processor definition file for Ghidra so that the firmware could be reverse-engineered. This got him to the point of understanding 1806 assembly well enough that he was able to re-flash the phone to print debugging messages on the built-in 16×2 LCD screen, which allowed him to figure out which routines were being called under various error conditions.

It doesn’t appear that [Inbar] ever completed the reverse engineering project, but as he points out, what does that even mean? He got inside, took a look around, and made the phone do some cool things it couldn’t do before, and in the process made things easier for anyone working with 1806 processors in Ghidra. That’s a pretty complete win in our books.

Apollo-era PCB Reverse Engineering To KiCad

November 25, 2024 by Chris Lott 24 Comments

Earlier this year [Skyhawkson] got ahold of an Apollo-era printed circuit board which he believes was used in a NASA test stand. He took high quality photos of both sides of the board and superimposed them atop each other. After digging into a few obsolete parts from the 1960s, he was able to trace out the connections. I ran across the project just after making schematics for the Supercon badge and petal matrix. Being on a roll, I decided to take [Skyhawkson]’s work as a starting point and create KiCad schematics. Hopefully we can figure out what this circuit board does along the way.

The board is pretty simple:

approximately 6.5 x 4.5 inches
22 circuit edge connector 0.156 in pitch
31 ea two-terminal parts ( resistors, diodes )
3 ea trimmer potentiometers
7 ea transistors
parts arranged in 4 columns

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Supercon 2024 SAO Petal KiCad Redrawing Project

November 19, 2024 by Chris Lott 4 Comments

Last week I completed the SAO flower badge redrawing task, making a complete KiCad project. Most of the SAO petals are already released as KiCad projects, except for the Petal Matrix. The design features 56 LEDs arranged in eight spiral arms radiating from the center. What it does not feature are straight lines, right angles, nor parts placed on a regular grid.

Importing into KiCad

Circuit Notes for LEDs, Thanks to [spereinabox]

I followed the same procedures as the main flower badge with no major hiccups. This design didn’t have any released schematics, but backing out the circuits was straightforward. It also helped that user [sphereinabox] over on the Hackaday Discord server had rung out the LED matrix connections and gave me his notes.

Grep Those Positons

I first wanted to only read the data from the LEDs for analysis, and I didn’t need the full Kicad + Python scripting for that. Using grep on the PCB file, you get a text file that can be easily parsed to get the numbers. I confirmed that the LED placements were truly as irregular as they looked.

My biggest worry was how obtain and re-apply the positions and angles of the LEDs, given the irregular layout of the spiral arms. Just like the random angles of six SAO connector on the badge board, [Voja] doesn’t disappoint on this board, either. I fired up Python and used Matplotlib to get a visual perspective of the randomness of the placements, as one does. Due to the overall shape of the arms, there is a general trend to the numbers. But no obvious equation is discernable.

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Bypassing Airpods Hearing Aid Georestriction With A Faraday Cage

November 15, 2024 by Maya Posch 53 Comments

When Apple recently announced the hearing aid feature on their new AirPods Pro 2, it got the attention of quite a few people. Among these were [Rithwik Jayasimha] and friends, with [Rithwik] getting a pair together with his dad for use by his hard-of-hearing grandmother. That’s when he found out that this feature is effectively limited to the US and a small number of other countries due them being ‘regulated health features’, per Apple. With India not being on the approved countries list and with no interest in official approval legalities, [Rithwik] set to work to devise a way to bypass this restriction.

As noted in the blog post, the primary reason for using AirPods here instead of official hearing aids is due to the cost of the latter, which makes them a steal for anyone who is dealing with mild to moderate hearing loss. Following the official Hearing Aid feature setup instructions requires that your location is detected as being in an approved country. If it is, the Health App (on iOS 18.1) will popup a ‘Get Started’ screen. The challenge was thus to make the iOS device believe that it was actually in the FDA-blessed US and not India.

Merely spoofing the location and locale didn’t work, so the next step was to put the iOS device into a Faraday cage along with an ESP32 that broadcast California-based WiFi SSIDs. Once the thus treated iPad rebooted into the US, it could be used to enable the hearing aid feature. Next [Rithwik] and friends created a more streamlined setup and procedure to make it possible for others to replicate this feat.

As also noted in the blog post, the Hearing Aid feature is essentially a specially tuned Transparency mode preset, which is why using AirPods for this feature has been a thing for a while, but with this preset it’s much better tuned for cases of hearing loss.

Bluetooth Dongle Gives Up Its Secrets With Quick Snooping Hack

November 14, 2024 by Dan Maloney 5 Comments

There’s a lot going on in our wireless world, and the number of packets whizzing back and forth between our devices is staggering. All this information can be a rich vein to mine for IoT hackers, but how do you zero in on the information that matters? That depends, of course, but if your application involves Bluetooth, you might be able to snoop in on the conversation relatively easily.

By way of explanation, we turn to [Mark Hughes] and his Boondock Echo, a device we’ve featured in these pages before. [Mark] needed to know how long the Echo would operate when powered by a battery bank, as well as specifics about the power draw over time. He had one of those Fnirsi USB power meter dongles, the kind that talks to a smartphone app over Bluetooth. To tap into the conversation, he enabled Host Control Interface logging on his phone and let the dongle and the app talk for a bit. The captured log file was then filtered through WireShark, leaving behind a list of all the Bluetooth packets to and from the dongle’s address.

That’s when the fun began. Using a little wetware pattern recognition, [Mark] was able to figure out the basic structure of each frame. Knowing the voltage range of USB power delivery helped him find the bytes representing voltage and current, which allowed him to throw together a Python program to talk to the dongle in real-time and get the critical numbers.

It’s not likely that all BLE-connected devices will be as amenable to reverse engineering as this dongle was, but this is still a great technique to keep in mind. We’ve got a couple of applications for this in mind already, in fact.

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