Author: Lewin Day

3425 Articles

34-Year-Old Macintosh ROM Bug Revealed By Emulator

December 7, 2025 by No comments

Generally, you’d hope that your computer manufacturer got the ROM just right before shipping your computer. As [Doug Brown] found out, Apple actually fumbled this with the release of the Macintosh Classic II several decades ago. And yet… the machines worked! That turns out to be due to a rather weird low-level quirk, as recent tinkering in an emulator revealed. 

The bug was revealed when [Doug] was experimenting with the emulated Macintosh Classic II in MAME. He was exploring keyboard shortcuts for launching the debugger, but soon found a problem. He needed to load MacsBug to enable the debugging shortcut, and that required the use of 32-bit addressing. However, the emulated system wouldn’t boot in this mode at all, instead landing on a Sad Mac error screen.

Heavy debugging ensued, which makes for great reading if you love to chase problems on an instruction-by-instruction basis. Ultimately, [Doug’s] conclusion was a mindboggling one. He determined that the crash in MAME came down to a difference between the emulator’s behaviour versus the original Motorola 68030 CPU in the Classic II. There was simply a problematic undocumented instruction baked into the ROM. The real CPU runs this undocumented instruction, which modifies a certain register, allowing boot without issue. Meanwhile, the emulated CPU tries to execute the bad instruction, fails to modify the right register, and everything falls in a heap. [Doug] speculates that had the 68030 CPU hadn’t hidden the bug, Apple’s engineers might have found it many years ago. He even proved his theory by whipping up multiple custom ROMs to verify what was going on.

We love it when bugs from decades past rear their heads; we love it even more when they get fixed. If you’re chasing down issues with an Amiga or you’re ironing out the kinks in software for the Acorn Archimedes, be sure to let us know on the tips line.

[via Tom’s Hardware, thanks to Jason Morris for the tip!]

A Touchscreen MIDI Controller For The DIY Set

December 7, 2025 by 6 Comments

MIDI controllers are easy to come by these days. Many modern keyboards have USB functionality in this regard, and there are all kinds of pads and gadgets that will spit out MIDI, too. But you might also like to build your own, like this touchscreen design from [Nick Culbertson].

The build takes advantage of a device colloquially called the Cheap Yellow Display. It consists of a 320 x 240 TFT touchscreen combined with a built-in ESP32-WROOM-32, available under the part number ESP32-2432S028R.

Continue reading “A Touchscreen MIDI Controller For The DIY Set” →

Neat Techniques To Make Interactive Light Sculptures

December 7, 2025 by 21 Comments

[Voria Labs] has created a whole bunch of artworks referred to as Lumanoi Interactive Light Sculptures. A new video explains the hardware behind these beautiful glowing pieces, as well as the magic that makes their interactivity work.

The basic architecture of the Lumanoi pieces starts with a custom main control board, based around the ESP-32-S3-WROOM-2. It’s got two I2C buses onboard, as well as an extension port with some GPIO breakouts. The controller also has lots of protection features and can shut down the whole sculpture if needed. The main control board works in turn with a series of daisy-chained “cell” boards attached via a 20-pin ribbon cable. The cable carries 24-volt power, a bunch of grounds, and LED and UART data that can be passed from cell to cell. The cells are responsible for spitting out data to addressable LEDs that light the sculpture, and also have their own microcontrollers and photodiodes, allowing them to do all kinds of neat tricks.

Continue reading “Neat Techniques To Make Interactive Light Sculptures” →

The ZX Spectrum Finally Got An FPS

December 7, 2025 by 15 Comments

The ZX Spectrum is known for a lot of things, but it’s not really known for a rich and deep library of FPS titles. However, there is finally such a game for the platform, thanks to [Jakub Trznadel]—and it’s called World of Spells.

Like so many other games of this type, it was inspired by the 3D raycasting techniques made so popular by Wolfenstein 3D back in the day. For that reason, it has a very similar look in some regards, but a very different look in others—the latter mostly due to the characteristic palette available on the ZX Spectrum. A playable FPS is quite a feat to achieve on such limited hardware, but [Jakub] pulled it off well, with the engine able to reach up to 80 frames per second.

Continue reading “The ZX Spectrum Finally Got An FPS” →

Bridging RTL-433 To Home Assistant

December 6, 2025 by 18 Comments

If you’ve got an RTL-SDR compatible receiver, you’ve probably used it for picking up signals from all kinds of weird things. Now, [Jaron McDaniel] has built a tool to integrate many such devices into the world of Home Assistant.

It’s called RTL-HAOS, and it’s intended to act as a bridge. Whatever you can pick up using the RTL_433 tool, you can set up with Home Assistant using RTL-HAOS. If you’re unfamiliar with RTL_433, it’s a multitalented data receiver for picking up all sorts of stuff on a range of bands using RTL-SDR receivers, as well as a range of other hardware. While it’s most closely associated with products that communicate in the 433 MHz band, it can also work with products that talk in 868 MHz, 315 MHz, 345 MHz, and 915 MHz, assuming your hardware supports it. Out of the box, it’s capable of working with everything from keyless entry systems to thermostats, weather stations, and energy monitors. You can even use it to listen to the tire pressure monitors in your Fiat Abarth 124 Spider, if you’re so inclined.

[Jaron’s] tool integrates these devices nicely into Home Assistant, where they’ll appear automatically thanks to MQTT discovery. It also offers nice signal metrics like RSSI and SNR, so you can determine whether a given link is stable. You can even use multiple RTL-SDR dongles if you’re so inclined. If you’re eager to pull some existing environmental sensors into your smart home, this may prove a very easy way to do it.

The cool thing about Home Assistant is that hackers are always working to integrate more gear into the ecosystem. Oftentimes, they’re far faster and more efficient at doing this than big-name corporations. Meanwhile, if you’re working on your own hacks for this popular smart home platform, we’d probably like to know about it. Be sure to hit up the tips line in due time.

Garage Fridge Gets New DIY Controller

December 5, 2025 by 44 Comments

[Rick] had a problem. His garage refrigerator was tasked with a critical duty—keeping refreshing beverages at low temperature. Unfortunately, it had failed—the condenser was forever running, or not running at all. The beverages were either frozen, or lukewarm, regardless of the thermostat setting. There was nothing for it—the controller had to be rebuilt from scratch.

Thankfully, [Rick]’s junk drawer was obliging. He was able to find an Arduino Uno R4, complete with WiFi connectivity courtesy of the ESP32 microcontroller onboard. This was paired with a DHT11 sensor, which provided temperature and humidity measurements. [Rick] began testing the hardware by spitting out temperature readings on the Uno’s LED matrix.

Once that was working, the microcontroller had to be given control over the fridge itself. This was achieved by programming it to activate a Kasa brand smart plug, which could switch mains power to the fridge as needed. The Uno simply emulated the action of the Kasa phone app to switch the smart plug on and off to control the fridge’s temperature, with the fridge essentially running flat out whenever it was switched on. The Uno also logs temperature to a server so [Rick] can make sure temperatures remain in the proper range.

We’ve seen some great beverage-cooling hacks over the years. If you’ve mastered your own hacky methods of keeping the colas chilled, don’t hesitate to let us know on the tipsline.