Turning A MicroKORG Into A MicroKORG S With This Speaker Mod

June 5, 2020 by 11 Comments

When [Michael Wessel] bought his MicroKORG synthesizer/vocoder, he felt less than amused when two years later the MicroKORG S was released, with the ‘S’ standing for ‘sound’, apparently, for the 2+1 speaker system that was added to it. Undeterred, [Michael] figured out that both synthesizers are similar enough that one could likely add a similar speaker system to the original MicroKORG.

The similarities between the two products become apparent when one compares the original with its successor, with the latter seemingly mostly adding said speakers and more presets, along with a snazzy new exterior. (Although the 1970s styling of the original may have more fans.)  As the embedded video shows, this mod is fairly clean.

At the core of this mod is a PAM8403-based class D amplifier board. The PAM8403 is a 3 W audio amplifier, originally produced by Power Analog Microelectronics (now Diodes). While not an amazing amplifier, it lends itself well for battery-powered applications like the MicroKORG. Rounding out the build is a 7805 linear regulator to get 5 V for the PAM8403, a few filter capacitors, a switch to turn the speakers on/off, and of course the speakers.

Although there’s quite a bit of space in the enclosure, most speakers tend to be large enough that this can be a bit of a squeeze. [Michael] found some low-profile 20 W full-range speakers that seem to work well for this purpose. To finish wiring this up, all it takes is a hole saw and a way to get the audio output from the MicroKORG.

In this mod, [Michael] opted to get the audio from the output jack on the back, but for a cleaner result it probably could be wired straight into the on-board header.

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This Week In Security: Exim, Apple Sign-in, Cursed Wallpaper, And Nuclear Secrets

June 5, 2020 by 9 Comments

So first off, remember the Unc0ver vulnerability/jailbreak from last week? In the 13.5.1 iOS release, the underlying flaw was fixed, closing the jailbreak. If you intend to jailbreak your iOS device, make sure not to install this update. That said, the normal warning applies: Be very careful about running out-of-date software.

Apple Sign In

An exploit in Apple’s web authentication protocol was fixed in the past week . Sign In With Apple is similar to OAuth, and allows using an Apple account to sign in to other sites and services. Under the hood, a JSON Web Token (JWT) gets generated and passed around, in order to confirm the user’s identity. In theory, this scheme even allows authentication without disclosing the user’s email address.

So what could go wrong? Apparently a simple request for a JWT that’s signed with Apple’s public key will automatically be approved. Yeah, it was that bad. Any account linked to an Apple ID could be trivially compromised. It was fixed this past week, after being found and reported by [Bhavuk Jain]. Continue reading “This Week In Security: Exim, Apple Sign-in, Cursed Wallpaper, And Nuclear Secrets” →

Tic-Tac-Toe Implemented In Single Call To Printf()

June 5, 2020 by 34 Comments

[Nicholas Carlini] programmed a C implementation of two-player Tic Tac Toe, and he did it in a single call to printf(). The arguments for that single function call get mind-bendingly complex, so it may come as no surprise that it was written for The International Obfuscated C Code Contest (IOCCC).

Most of us are aware that printf() is one of those functions that is considerably more complex under the hood, and capable of far more, than it may appear to be. But did you know that it is capable of Turing-complete computation?

[Nicholas] clearly steps through the theory, so give it a read. In short, a maze of arguments handles the logic of the game while an embedded scanf() reads user input, and printing the game board is always preceded by an escape code to clear the screen.

[Nicholas] is certainly no stranger to in-depth understandings; we’ve seen his work before in demonstrating how to fool speech recognition with hidden commands, including a powerful example showing how two virtually identical-sounding audio files transcribe entirely differently.

How Did They Get Sampled Sounds From An SN76489 8-bit Sound Chip?

June 5, 2020 by 23 Comments

If you were lucky and had well-off parents in the early 1980s, your home computer had a sound chip on board and could make music. There were a variety of chips on the market that combined in some form the tone generators and noise sources of a synthesiser, but without the digital-to-analogue converters of later sound chips designed for sampled audio. They gave birth to chiptune music, but that was all they were made to do. The essence of a hack lies in making something perform in a way it was never intended to, and some game developers for the Acorn BBC Micro had its SN76489 producing sampled audio when it should never have been possible. How did they do it? It’s a topic [Chris Evans] has investigated thoroughly, and his write-up makes for a fascinating explanation.

So, how can a set of audio tone generators be turned into a sampled audio player, and how can it be done when the CPU is a relatively puny 6502? There’s no processor bandwidth for clever Fourier transform tricks, and 1980s tech isn’t set up for high data bandwidths. The answer lies in making best use of the controls the chip does offer, namely frequency and volume of a tone. A single cycle of a tone can be given a volume, and thus can be treated as a single sample of an unintended DAC. By using a tone frequency well above the audio range a suitable sample frequency can be found, and thus an audio stream can be played. The write-up has links to some examples in an emulator, and while they’re hardly hi-fi they’re better than you might expect for the hardware involved. Still, even at that they don’t approach this amazing 48kHz playback on a Commodore 64.

Header: SN76489, on a Colecovision console motherboard. Evan-Amos / Public domain.

Nintendo’s GBA Dev Board Could Pass For Modern DIY

June 4, 2020 by 10 Comments

When the Game Boy Advance came on the scene in 2001, it was a pretty big deal. The 32-bit handheld represented the single biggest upgrade the iconic Game Boy line had ever received, not only in terms of raw processing power, but overall design. It would set the state-of-the-art in portable gaming for years, and Nintendo was eager to get developers on board.

Which could explain why the official GBA development kit, recently shown off by [Hard4Games], looks like something that was built in a hackerspace. It’s pretty common for console development systems to look more like boxy 1990s computers than the sleek injection molded units that eventually take up residence under your television, but they don’t often come in the form of a bare PCB. It seems that Nintendo was in such a rush to get an early version of their latest handheld’s guts out to developers that they couldn’t even take the time to get a sheet metal case stamped out for it.

The development board doesn’t like later GBA games.

All of the principle parts of the final GBA are here, and as demonstrated in the video after the break, the board even plays commercially released games. Though [Hard4Games] did find that some titles from the later part of the handheld’s life had unusual graphical glitches; hinting that there are likely some low-level differences that don’t manifest themselves unless the developer was really digging deep to squeeze out all the performance they could.

The board also lacks support for Game Boy and Game Boy Color games, though this is not wholly surprising. When an older game was inserted into a GBA, the cartridge would physically depress a switch that enabled a special 8080-based coprocessor that existed solely for backwards compatibility. Adding that hardware to a development board would have made it more expensive and added no practical benefit. That said, [Hard4Games] does point out that there appears to be a unpopulated area of the board where the backwards compatibility switch could have been mounted.

Hackers have always been enamored with the Game Boy, so it’s fitting to see that the official development kit for the final entry into that storied line of handhelds looked a lot like something they could build themselves. If anyone feels inclined to build their own “deconstructed” GBA in this style, you know where to find us.

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Palm’s Mini-Mobile Phone Becomes Bike Phone

June 4, 2020 by 16 Comments

The mini-mobile phone [Jim Yang] got his hands on deserves a bit of background. Palm had the concept of a companion mobile phone, and this manifested itself in late 2018 as a cute palm-sized smartphone that one could carry around when one didn’t wish to haul along their “real” phone. This smaller and simpler phone was originally intended to share the same mobile number as one’s primary phone (though it has since been made able to work as a standalone device.)

[Jim]’s device, in use as a bike-mounted smartphone.
[Jim] got his hands on a refurbished Palm PVG100, rooted it, and shared some pictures of the internal components. The phone was not carrier-locked, but getting it up and running was still a bit more complex than plugging in a SIM card. For example, voice calls worked fine but to gain access to mobile data on the Three UK mobile network required updating the Access Point Name (APN) settings. [Jim] also rooted the Android-based phone and describes how he removed Verizon bloatware.

Palm’s companion phone idea hasn’t really caught on in a commercial sense, but in a way, [Jim] is validating the concept. After getting it up and running, he attached it to his bike with a custom mount to enjoy the benefits of having a mobile phone along without actually risking his primary device.

In case you’re wondering, this Palm is indeed the same Palm that launched the PalmPilot in 1996, whose distinctive folding keyboard accessory has shown up in past hacks.

Contactless Doorbell Built To Avoid Coronavirus

June 4, 2020 by 15 Comments

It’s often said that necessity breeds creativity, and during a global pandemic such words have proved truer than ever. Realising the common doorbell could be a potential surface transmission point for coronavirus, [CasperHuang] whipped up a quick build.

The build eschews the typical pushbutton we’re all familiar with. Instead, it relies on an ultrasonic distance sensor to detect a hand (or foot) waved in front of the door. An Arduino Leonardo runs the show, sounding a buzzer when the ultrasonic sensor is triggered. In order to avoid modifying the apartment door, the build is housed in a pair of cardboard boxes, taped to the base of the door, with wires passing underneath.

It’s a tidy way to handle contactless deliveries. We imagine little touches like this may become far more common in future design, as the world learns lessons from the COVID-19 pandemic. Every little bit helps, after all. Video after the break.

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