Making A Crystodyne Radio With Zinc Oxide And Cat’s Whiskers

March 5, 2024 by Maya Posch 19 Comments

Zinc negative resistance oscillator circuit. (Credit: Ashish Derhgawen)

During the first half of the 20th century radio technology was booming, albeit restricted by the vacuum tube technology of the time which made radios cumbersome in size and power needs. The development of a solid state alternative to the vacuum tube was in full swing, but the first version pioneered by [Oleg Losev] in the form of crystal radios failed to compete. Even so these ‘crystal radios’ laid much of the groundwork for subsequent research. The ease of creating this type of radio also makes it a fun physics experiment today, as [Ashish Derhgawen] demonstrates in a blog post.

In the January 1925 issue of Radio News the theory of the circuit is explained by [Oleg Losev] himself (page 1167). At the core is a material capable of negative resistance, as a non-linear (non-Ohmic) material, which means that the current passing through them decreases as voltage increases over part of their I-V curve. This enables it to work as an amplifier or oscillator. After the cessation of research on crystal radio technology by [Losev] and others, the negative resistance diode was rediscovered in 1957 with the tunnel diode.

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Gaming On A TP-Link TL-WDR4900 Wireless Router

March 5, 2024 by Maya Posch 18 Comments

When you look at your home router, the first thought that comes to mind probably isn’t about playing games on it. But that doesn’t stop [Manawyrm] and [tSYS] from taking on the task of turning the 2013-era TP-Link TL-WDR4900 router into a proper gaming machine using an external GPU. This is made possible by the PCIe lanes on the mainboard, courtesy of the PowerPC-based SoC (NXP QorIQ P1014) and remappable Base Address Registers (BARs). This router has been an OpenWRT-favorite for years due to its powerful hardware and feature set.

This mod required a custom miniPCIe PCB that got connected to the PCIe traces (after cutting the connection with the Atheros WiFi chipset). This allowed an external AMD Radeon HD 7470 GPU to be connected to the system, which showed up in OpenWRT. To make full use of this hardware by gaining access to the AMD GPU driver, full Debian Linux was needed. Fortunately, the distro had a special PowerPCSPE port that supports the e500v2 CPU core in the SoC. After this it was found that the amdgpu driver has issues on 32-bit platforms, for which an issue ticket got filed.

Using the legacy Radeon driver helped to overcome this issue, but then it was found that the big endian nature of the CPU tripped up the Grand Theft Auto: Vice City game code which has not been written with BE in mind. This took a lot of code patching to help fix this, but eventually the game was up and running, albeit with glitches. Whatever the cause of these graphical glitches was will remain unknown, as after updating everything things began to work normally.

So now it’s possible to convert a 2013-era router into a gaming console after patching in an external GPU, which actually could be useful in keeping more potential e-waste out of landfills.

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Hacking An Actual WiFi Toothbrush With An ESP32-C3

March 5, 2024 by Maya Posch 15 Comments

Following on the heels of a fortunately not real DDoS botnet composed of electric toothbrushes, [Aaron Christophel] got his hands on a sort-of-electric toothbrush which could totally be exploited for this purpose.

Evowera Planck Mini will never gonna give you up, never let you down. (Credit: Aaron Christophel)

The Evowera Planck Mini which he got is the smaller, children-oriented version of the Planck O1 (a more regular electric toothbrush). Both have a 0.96″ color LC display, but the O1 only has Bluetooth and requires a smartphone app. Meanwhile the Mini uses a pressure sensor for the brush along with motion sensors to keep track of the child’s teeth brushing efforts and to provide incentives.

The WiFi feature of the Mini appears to be for both firmware updates as well as to allow parents to monitor the brushing reports of their offspring in the associated smartphone app. With this feature provided by the ESP32-C3 SoC inside the device, the question was how secure it is.

As it turns out not very secure, with [Aaron] covering the exploit in a Twitter thread. As exploits go, it’s pretty straightforward: the toothbrush tries to connect to a default WiFi network (SSID evowera, pass 12345678), tries to acquire new firmware, and flashes this when found without any fuss. [Aaron] made sure to figure out the pin-out on the PCB inside the device as well, opening up new avenues for future hacking.

We’re great fans of [Aaron] and his efforts to breathe new life into gadgets through firmware hacking. His replacement firmware for the Xiaomi LYWSD03MMC Bluetooth thermometer is one of the best we’ve seen.

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Cybiko Repair-A-Thon With Memory Upgrade

March 2, 2024 by Maya Posch 9 Comments

Concluding a four-part repair-a-thon on a stack of Cybiko handheld computers, [Robert] over at Robert’s Retro covered the intricate details of fixing a last batch of four in a nearly one-hour long video. These devices, with their colorful transparent cases, are a great time capsule of the early 2000s. Even with their limited hardware, they provided PDA-like capabilities to teens years before smartphones were a thing, with features including music playback and wireless chat (albeit limited to recipients within 100 meters).

Of the four units covered in this video, they are all the original Cybiko Classic, with two each of the first and second revision, none of which were booting due to a bad Flash chip. Another issue was the dead rumble motors on them, which fortunately are the easiest to replace. One of the units also has a dead display, which did not get replaced this time around.

Insides of a Cybiko Classic (Credit: Robert's Retro, YouTube) — Insides of a Cybiko Classic (Credit: Robert’s Retro, YouTube)

The flash chip replacement was a bit more of a headache, as these devices don’t just take any chip, mostly due to how much the system relies on the ready-busy line. This led [Robert] to replace the old 4 Mb AT45DB041 chips with the 16 Mb Atmel AT45DB161. Previously he had taken 1 MB chips from an expansion cartridge to replace more dead flash chips, so those were replaced with 2 MB chips.

With fresh flash in place, the next challenge was to get these written with a firmware image, with the v2 Cybiko units already having CyOS on the separate 256 kB Flash chip, but the v1 units relying on the single big Flash chip for all storage. Fortunately, an enterprising member of the community developed a tool to ease this ordeal by allowing a Cybiko unit in its serial dock to be flashed with no issues, other than the 2 MB Flash causing some issues as this was a previously unknown hardware configuration.

[Robert] now has four working Cybiko units, with one being headless due to the busted screen, and more room for apps on the 2 MB units than a 2000s teenager would have known what to do with.

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On The Merits Of A Solid-State Dehumidifier Filament Dry Box

March 2, 2024 by Maya Posch 44 Comments

How good are ion membrane dehumidifiers for keeping FDM filament dry and ready for printing? This is the question which [Stefan] at CNC Kitchen sought to answer in a recent video. Like many of us, he was inspired by a video which [Big Clive] made a while ago in which said dehumidifiers were demonstrated for keeping an enclosure free from moisture. Yet would they be able to tackle the much bigger drying job of one or more spools of filament? Thanks to some free samples sent by Rosahl, [Stefan] was able to start answering this question.

Performance of desiccants and dehumidifier element. (Credit CNC Kitchen)

In the experiments, he used the smaller RS1 (€36.25 a piece) for a single spool container, and the larger MDL-3 (€169) with a Bambu Lab AMS multi-spool unit. Normally such an AMS has three big containers with silica desiccant in it that have to be regularly swapped out, but he modified one AMS to only have the big MDL-3 membrane to dehumidify. A second AMS was left with older silica in its containers, and a third got fresh silica, allowing for some benchmarking between the three units.

The results say a lot, with the initial empty AMS test showing the older silica desiccants topping out quickly and leaving the fresh silica and the membrane dehumidifier to go neck to neck. This is not the usual scenario in which you’d use these dehumidification methods of course, and the small-scale test with the RS1 showed that with a full filament spool in the box, humidity inside the container would only drop very gradually as more and more moisture replaced what was removed from the air. In particular the cardboard element of the spool being used was suspected of being one of the biggest sources of moisture.

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Easily Add Link Cable Support To Your Homebrew GBA Game

February 29, 2024 by Maya Posch 7 Comments

The Game Boy Advance (GBA) link cable is the third generation of this feature which originated with the Gameboy. It not only allows for peripherals to be connected, but also for multiplayer between GBAs – even with just one game copy – and item sharing and unlocking of features in specific games. This makes it an interesting feature to support in today’s homebrew GBA games and applications, made easy by libraries such as [Rodrigo Alfonso]’s gba-link-connection.

This C++ library can be used in a number of ways: either limited to just the physical link cable, just the wireless link option or both (universal link). These support either 4 (cable) or 5 (wireless) players to be connected simultaneously. As additional options there are the LinkGPIO.hpp and LinkSPI.hpp headers which allow the link port to be used either as a generic GPIO, or as an SPI link (up to 2 Mb/s). The multiboot feature where a single ROM image is shared among connected GBAs is supported with both wired and wireless links.

It’s heartening to see that a device which this year celebrates its 23rd birthday is still supported so well.

Thanks to [gudenau] for the tip.

The White House Memory Safety Appeal Is A Security Red Herring

February 29, 2024 by Maya Posch 107 Comments

In the Holy Programming Language Wars, the lingua franca of system programming – also known as C – is often lambasted for being unsecure, error-prone, and plagued with more types of behavior that are undefined than ones that are defined by the C standards. Many programming languages were said to be ‘C killers’, yet C is still alive today. That didn’t stop the US White House’s Office of the National Cyber Director (ONCD) from putting out a report in which both C and C++ got lambasted for being ‘unsafe’ when it came to memory management.

The full report (PDF) is pretty light on technical details, while citing only blog posts by Microsoft and Google as its ‘expert sources’. The claim that memory safety issues are the primary cause of CVEs is not substantiated, or at least ignores the severity of CVEs when looking at the CISA statistics for active exploits. Beyond this call for ‘memory safety’, the report then goes on to effectively call for more testing and validation, while kicking in doors that were opened back in the 1970s already with the Steelman requirements and the High Order Language Working Group (HOLWG) of 1975.

What truly is the impact and factual basis of the ONCD report?

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