A microwave imaging setup. On the left is a monitor displaying a monochrome GUI. In the center is the RP2040-based positioning and measurement system, and on the right is a vector network analyzer.

Precise Positioning With The RP2040

January 1, 2024 by Stephen Ogier 10 Comments

Microwave imaging is similar to CT imaging, but instead of X-rays, the microwaves are used to probe the structure and composition of an object. To facilitate experimentation with microwave imaging, [Zehao Li] and [Kapil Gangwar] developed a system based on the RP2040 to control the height and rotation of a test object.

Their control system has a refreshingly physical user interface—a keypad. The keypad is used to configure the object’s position and the scanning step size, while user menus and the sample position are displayed in a clean and uncluttered interface over VGA. The RP2040 runs a multi-threaded program to handle user input, VGA display, and precise driving of two stepper motors for sample positioning.

The microwave imaging was performed by measuring the RF transmission over 2.5-8 GHz between two Vivaldi antennas on either side of the sample at a variety of angles. 2D cross-sections of the test object were reconstructed in Matlab using filtered back-projection. In this proof-of-concept demonstration, a commercial vector network analyzer was used to collect the data, but one could imagine migrating to a software defined radio (SDR) in the future.

A video demonstrating the system is embedded below the break. If you’re interested in DIY radio imaging, you might be interested in this guide to building your own synthetic aperture radar setup, or this analysis of an automotive radar chip.

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Sound-Reactive Light Saber Flips Allegiance Via Vowel Sounds

December 29, 2023 by Donald Papp 4 Comments

Students [Berk Gokmen] and [Justin Green] developed an RP2040-based LED-illuminated lightsaber as a final project with a bit of a twist. It has two unusual sound-reactive modes: disco mode, and vowel detection mode.

Switching allegiances (or saber color, at least) is only a sound away.

Disco mode alters the color of the saber dynamically in response to incoming sounds. Color and brightness are altered in response to incoming frequencies picked up by the on-board microphone, making a dynamic light show that responds particularly well to music.

The second mode is vowel detection, and changes the lightsaber’s color depending on spoken sounds. The “ee” sound makes the saber red, and the “ah” sound turns it blue. This method requires a lot of processing and filtering, and in the end it works, but is quite dependent on individual speakers for calibration.

The sound functionality centers around FFTs (Fast Fourier Transforms) which are fundamental to processing signals like audio in a meaningful way, and is a method accessible to embedded devices like microcontrollers with ADCs.

The lightsaber is battery-powered and wireless, and there are loads of details about the finer points of the design (including challenges and tradeoffs) on the project page, and the source code is available on GitHub. A video demonstration and walkthrough is embedded below.

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CoreXY On The Pi Pico

December 28, 2023 by Jenny List 8 Comments

There are enough off-the-shelf CoreXY mechanisms out there that for the cost of an AliExpress order it’s possible to quickly and cheaply make yourself a plotter. But [Koushani Das], [Mahathi Andavolu] and [Dengyu Tu] are completing their project for Cornell University’s ECE 5730 course, so of course they have designed one from the ground up. Happily for us it seems to be fairly easy to replicate, so you can build one too if it takes your fancy.

The write-up makes for an interesting dive into the nitty-gritty of design, for which we hope they managed to secure a decent grade. The hardware itself seems pretty straightforward as does the pair of stepper controllers and RP2040 they use to run the thing, and their explanation of the math behind the CoreXY coordinate system is genuinely interesting for those of us who’ve never taken the time to consider it.

All the good stuff can be found in a GitHub repository if you’d like to take this further, and meanwhile they’ve also put up a demo video which you can see below the break. We like this little plotter, and we hope others will take its design and run with it.

Want more CoreXY explanation? We’re happy to oblige.

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Several Raspberry Pi Picos connected to each other

Raspberry Pi Pico Parallel Mandelbrot Computation

December 27, 2023 by Julian Scheffers 11 Comments

The Mandelbrot set is — when visualized with some colors — an interesting shape with infinite detail. While the patterns are immediately obvious to the human eye, anyone who’s run one can tell you that they’re pretty computationally expensive to produce. Fortunately, as with many things in graphics, rendering the Mandelbrot set can be easily parallelized.

That’s what [rak277] and [ir93] demonstrate in their RP2040-based finals project. Computron, as they call it, is a network of Raspberry Pi Picos that work together to compute a visualization of the Mandelbrot set and show it on a VGA display. The Computron is made of two or more “math units” and one “projection unit”. The math units communicate over a shared I²C bus with the projection unit to first divide the workload and then compute their share of the work.

This project shows both the strengths and limitations of parallel computation. It makes use of multiple math units on a highly parallelizable workload, but as more math units are added there are diminishing performance gains due to the increased communications load on the network, which [rak277] and [ir93] suspect to be the current bottleneck in the Computron.

If you’re fresh out of Pi Picos, and don’t mind waiting awhile, you could always crank out a Mandelbrot set on your trusty Atari 800 in BASIC.

An exploded view render of a red 3D printed case with a green PCB is inside with visible USB-A connectors with a mouse and keyboard graphic above each and "A" and "B" labels above USB-C connectors on the other side.

Building A Better Keyboard And Mouse Switch

December 26, 2023 by Navarre Bartz 38 Comments

Switching inputs between desktops seems like something that should be simple but can prove to be a pain in reality. [Hrvoje Cavrak] decided to take matters into his own hands and build a better keyboard and mouse switch.

DeskHop is built from two Raspberry Pi Pico boards connected via UART and separated by an Analog Devices ADuM1201 dual-channel digital isolator. Through the magic of Pico-PIO-USB these RP2040s can be both host and device. To keep things simple, the PCB is single-sided, and the BOM only has five distinct components.

Once hooked up to your Windows, Mac, or Linux device, your mouse pointer “magically” goes from one screen to the other when dragged across the screen edge. Keyboard LEDs can be reprogrammed to indicate which device is active, and the real beauty of the device is that since it’s a hardware solution, you don’t have to install any software on a computer you might not have admin access to.

If you want to see some more ideas for keyboard and mouse switching, check out this Pi KVM with ATX signaling, this USB triplexer, or this Pi KVM on a PCIe card.

Open Source DC UPS Keeps The Low-Voltage Gear Going

December 22, 2023 by Dan Maloney 26 Comments

We all like to keep our network gear running during a power outage — trouble is, your standard consumer-grade uninterruptible power supply (UPS) tends to be overkill for routers and such. Their outlet strips built quickly get crowded with wall-warts, and why bother converting from DC to AC only to convert back again?

This common conundrum is the inspiration for [Walker]’s DC UPS design, which has some interesting features. First off, the design is open source, which of course invites tinkering and repurposing. The UPS is built for a 12 volt supply and load, but that obviously can be changed to suit your needs. The battery bank is a 4S3P design using 18650 cells, and that could be customized as well. There’s an ideal diode controller that prevents DC from back-feeding into the supply when the lights go out, and a really interesting synchronous buck-boost converter in place of the power management chip you’d normally see in a UPS. The converter chip takes a PWM signal from an RP2040; there’s also an ESP32 onboard for web server and UI duties as well as an STM32 to run the BMS. The video below discusses the design and shows a little of the build.

We’ve seen a spate of DC UPS designs lately, some more elaborate than others. This one has quite a few interesting chips that most of us don’t normally deal with, and it’s nice to see how they’re used in a practical design.

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A bald white man stands behind a table with an Apple II, a large green PCB, and a modular purple and black development board system. Atop the Apple II is what appears to be a smaller Apple II complete with beige case and brown fake keyboard.

Mini Apple IIe Now Fully Functional

December 5, 2023 by Navarre Bartz 1 Comment

Here at Hackaday, we love living in a future with miniaturized versions of our favorite retrocomputers. [James Lewis] has given us another with his fully functional Apple IIe from the Mega II chip.

When we last checked in on the Mega IIe, it was only just booting and had a ways to go before being a fully functional Apple II. We really love the modular dev board he designed to do the extensive debugging required to make this whole thing work. Each of the boards is connected with jumper pins, which [Lewis] admits would have been better as edge connectors since he should’ve known he’d be unplugging and replugging them more than he’d like.

This modular prototyping system paid dividends late in the project when a “MEGA bug” threatened the stability of the entire system. Since it was confined to the keyboard PCB, [Lewis] was able to correct the error and, swapping for the third revision of the board, everything that had been crashing the system now ran.

There were still some issues going to the final unified PCB that nearly made him give up on the project, but perseverance paid off in the end. Combining vintage chips and multiple RP2040s isn’t for the feint of heart.

Now that you have a more conveniently-sized Apple II, why not teach it some new tricks like digital photography or ChatGPT?

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