Multitasking On The Humble Z80 CPU

Multitasking is something we take for granted these days. Just about every computer we use, from our desktops to our phones, is capable of multitasking. It might sound silly to implement multitasking on lower-spec machines from many decades ago, given their limited resources, but it can be done, as [bchiha] demonstrates on a Z80-based machine.

[bchiha] has achieved pre-emptive multitasking on the TEC-1G Z80 computer, a modern reimagining of the classic Talking Electronics TEC-1 from the 1980s. The proof of concept code allows running up to eight separate tasks at once. Task switching runs on interrupts, triggered at approximately 50 Hz. When an interrupt fires, the CPU registers are transferred onto that task’s stack, and the next task’s stack is swapped to the stack pointer to allow execution of the new task to proceed. There is an overhead, of course, with [bchiha] noting that the task swapping routine itself takes about 430 clock cycles to run in between tasks.

Multitasking took some time to appear on home computers for good reason—it’s not very useful unless you have a machine with enough power to practically run multiple tasks at once. While a Z80 machine like this can do multitasking, you’d better hope each task is pretty tiny to avoid each individual task taking forever to run.

[bchiha] has made the simple multitasking code available on Github for the curious. We’ve featured multitasking work on other unconventional platforms before, too, like the Arduino Uno. Video after the break.

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[Thanks to Stephen Walters for the tip!]

hackaday.com/2025/11/01/multit…

An Audio Brick For Your Smart Home

If you’ve ever wanted to pump sound to all the rooms of your house, you might use any one of a number of commercial solutions. Or, you could go the more DIY route and whip up something like the Esparagus Audio Brick built by [Andriy].

The concept is simple—it’s a small unit, roughly the size of a brick, which streams high-quality audio. It’s based around an ESP32, which pulls in digital audio over Wi-Fi or Ethernet. The microcontroller is hooked up to a TAS5825M DAC, which comes with a built-in amplifier for convenience. The Esparagus is designed for integration with Home Assistant, allowing for easy control as part of a smart home setup. It’s also compatible with Spotify Connect, AirPlay, and Snapcast—the latter of which provides excellent sync when using multiple units across several rooms.

Design files are available on Github for the curious. We’ve seen other neat projects in this space, before, too—like the charmingly-named OtterCast. Video after the break.

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hackaday.com/2025/11/01/an-aud…

Building a PV Solar-Powered Quadcopter

The solar-powered quadcopter from below. (Credit: Luke Maximo Bell)
One of the most frustrating parts about flying a quadcopter is having to regularly swap battery packs, as this massively limits what you can do with said quadcopter, never mind its effective range. Obviously, having the sun power said quadcopter during a nice sunny day would be a much better experience, but how workable is this really? While airplanes have used solar power to stay aloft practically indefinitely, a quadcopter needs significantly more power, so is it even possible? Recently, [Luke Maximo Bell] set out to give it a whirl.

His quadcopter build uses a large but very lightweight carbon fiber frame, with large 18″ propellers. This provides the required space and lift for the solar panel array, which uses 27 razor-thin panels in a 9×3 grid configuration supported by a lightweight support frame.

Due to the lightweight construction, the resulting quadcopter actually managed to fly using just the direct power from the panels. It should be noted however that it is an exceedingly fragile design, to the point that [Luke]’s cat broke a panel in the array when walking over it while it was lying upside-down on a table.

After this proof of concept, [Luke] intends to add more panels, as well as a battery to provide some buffer and autonomous flying hardware, with the goal of challenging the world record for the longest flying drone. For the rest of us, this might make for a pretty cool idea for a LoRaWAN mesh node or similar, where altitude and endurance would make for a great combo.

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hackaday.com/2025/11/01/buildi…

Vogtsbauernhof

Visited the Black Forest open air museum Vogtsbauernhof in 77793 Gutach / Germany. This is a huge areal that has several very old farm buildings, that have been carefully de- and reconstructed on this site. There are often also tours, demonstrations or hands-on activities how people used to live in the Black Forest area but as a half-timber nutter I’m mostly interested in the buildings. These are from various periods starting as early as 1407 (though that’s an often refurbished exception).

Shooting any sort of pictures with my smartphone camera was very hard because the insides of the buildings are unbelievable dark and hardly lit. I guess this is driving home a point in itself. Anyway I did my best to improve the photos somewhat with Darktable (not that I have any idea what I’m doing there). Also the galleries won’t syndicate so you’ll have to check the source for the pictures.

Here are some of the pictures that are very dark in reality.

We also looked at plenty of farm equipment, of course. In fact one of the farms is still operated and has livestock around.

One of the most interesting things I found was a “mini house” that is basically of fridge for milk. It utilizes a water stream to keep milk on the inside cold.

Some of these buildings simply look gorgeous on the outside but my kids were pretty certain that they’d not actually want to life in such a building. Beside the darkness on the inside one could also always feel how air makes it inside. There’s always a slight breeze, which is probably nice in the summertime but not so much in the wintertime. Especially with only a few places around to heat the buildings.

One of their major show pieces is probably the Schlössle von Effringen, which is basically a mini castle that has been remade again and again dating back to ~11C.

This is also where I shot most of my pictures. Sadly we were running out of time and I have to revisit this again so look at some things a little closer. And maybe leave the kids at home too. They don’t really have the required patience.

I also rather enjoyed the various kitchens, that were almost all “smoke kitchens” – means the smoke from the kitchen fire was used to conserve food. This is a very medieval thing to do. Sadly the pictures I made don’t do them justice since they are basically black holes, that cameras struggle hard with.

One of the things I enjoyed most are models of various buildings. I made many photos of these for inspiration. Maybe I’ll come back to recreating such buildings in the Rising World game one day.

And last some unsorted photos in portrait mode (ugh, it happens, mkay?)

Website of the museum is: vogtsbauernhof.de/en with plenty of more pictures and a 360deg tour. Can recommend. Alas bring food along – the restaurants next to the site are rather expensive. Museum is worth every cent though IMHO.

This content is licensed under a Creative Commons Attribution 4.0 International license.

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#Halftimber #timberframed

2025 Component Abuse Challenge: A Transistor As A Voltage Reference

For our 2025 Component Abuse Challenge there have been a set of entries which merely use a component for a purpose it wasn’t quite intended, and another which push misuse of a part into definite abuse territory, which damages or fundamentally changes it. [Ken Yap]’s use of a transistor base-emitter junction as a voltage reference certainly fits into the latter category.

If you forward bias a base-emitter junction, it will behave as a diode, which could be used as a roughly 0.7 volt reference. But this project is far more fun than that, because it runs the junctions in reverse biased breakdown mode. Using one of those cheap grab bags of transistor seconds, he finds that devices of the same type maintain the same voltage, which for the NPN devices he has works out at 9.5 volts and the PNP at 6.5. We’re told it damages their operation as transistors, but with a grab bag, that’s not quite the issue.

We’ve got a few days left before the end of the contest, and we’re sure you can think of something worth entering. Why not give it a go!

hackaday.com/2025/11/01/2025-c…