Direct Digital Synthesis (DDS)

Direct Digital Synthesis (DDS) Explained By [Bil Herd]

November 24, 2014 by 42 Comments

One of the acronyms you may hear thrown around is DDS which stands for Direct Digital Synthesis. DDS can be as simple as taking a digital value — a collection of ones and zeroes — and processing it through a Digital to Analog Converter (DAC) circuit. For example, if the digital source is the output of a counter that counts up to a maximum value and resets then the output of the DAC would be a ramp (analog signal) that increases in voltage until it resets back to its starting voltage.

This concept can be very useful for creating signals for use in a project or as a poor-man’s version of a signal or function generator. With this in mind I set out here to demonstrate some basic waveforms using programmable logic for flexibility, and a small collection of resistors to act as a cheap DAC. In the end I will also demonstrate an off-the-shelf and inexpensive DDS chip that can be used with any of the popular micro-controller boards available that support SPI serial communication.

All of the topics covered in the video are also discussed further after the break.

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Bil Herd: Computing With Analog

July 25, 2014 by 34 Comments

When I was young the first “computer” I ever owned was an analog computer built from a kit. It had a sloped plastic case which had three knobs with large numerical scales around them and a small center-null meter. To operate it I would dial in two numbers as indicated by the scales and then adjust the “answer” by rotating the third dial until the little meter centered. Underneath there was a small handful of components wired on a terminal strip including two or three transistors.

In thinking back about that relic from the early 1970’s there was a moment when I assumed they may have been using the transistors as logarithmic amplifiers meaning that it was able to multiply electronically. After a few minutes of thought I came to the conclusion that it was probably much simpler and was most likely a Wheatstone Bridge. That doesn’t mean it couldn’t multiply, it was probably the printed scales that were logarithmic, much like a slide rule.

Science Fair Analog Computer
Old meets new: Analog and digital computation

Did someone just ask what a slide rule was? Let me explain further for anyone under 50. If you watch the video footage or movies about the Apollo Space Program you won’t see any anyone carrying a hand calculator, they didn’t exist yet. Yet the navigation guys in the first row of Mission Control known aptly as “the trench”, could quickly calculate a position or vector to within a couple of decimal places, and they did it using sliding piece of bamboo or aluminum with numbers printed on them.

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Herd Single Cell Organisms With Your Mind

May 23, 2013 by 7 Comments

mind-controlled-paramecium

Most project tips involving brainwaves get passed over because it’s hard to make much out of that type of control. This project doesn’t necessarily make progress on the control side on this, but you have to admit that herding life forms with your thoughts deserves a closer look.

[Geva] set up a rig that allows him to interact with paramecium — tiny single cell organism that are happy to swim around all day long. Just like vertebrates they’re not big fans of electric shocks. Run some current through the fluid and they’ll swim toward the negative electrode.

This experiment uses four pencil leads as electrodes. These are driven by an Arduino which reacts to the input from a toy brain wave device. Concentrate in just the right way and they will swim wherever you will them to.

This isn’t quite as involved as cockroach mind control, but it’s every bit as interesting
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The Hackaday Summer Reading List: No AI Involvement, Guaranteed

July 7, 2025 by 43 Comments

If you have any empathy at all for those of us in the journalistic profession, have some pity for the poor editor at the Chicago Sun-Times, who let through an AI-generated summer reading list made up of novels which didn’t exist.  The fake works all had real authors and thus looked plausible, thus we expect that librarians and booksellers throughout the paper’s distribution area were left scratching their heads as to why they’re not in the catalogue.

Here at Hackaday we’re refreshingly meat-based, so with a guarantee of no machine involvement, we’d like to present our own summer reading list. They’re none of them new works but we think you’ll find them as entertaining, informative, or downright useful as we did when we read them. What are you reading this summer? Continue reading “The Hackaday Summer Reading List: No AI Involvement, Guaranteed” →

Adaptive Keyboards & Writing Technologies For One-Handed Users

June 15, 2025 by 12 Comments

After having been involved in an accident, [Kurt Kohlstedt] suffered peripheral neuropathy due to severe damage to his right brachial plexus — the network of nerves that ultimately control the shoulder, arm, and hand. This resulted in numbness and paralysis in his right shoulder and arm, with the prognosis being a partial recovery at best. As a writer, this meant facing the most visceral fear possible of writing long-form content no longer being possible. While searching for solutions, [Kurt] looked at various options, including speech-to-text (STT), before focusing on single-handed keyboard options. Continue reading “Adaptive Keyboards & Writing Technologies For One-Handed Users” →

Wireless Power Makes For Cable-Free Desk

June 8, 2025 by 33 Comments

Some people hate cables with a passion; others are agnostic and prefer cabled peripherals to having to stop and charge their mouse. [Matt] from DIYPerks has the best of both worlds with this wireless-powered, no-cable desk setup.

The secret is embedded within the plywood desk: an evaluation kit from Etherdyne Technologies, Inc consisting of a 100 W RF power supply and its associated power antenna looping around the desktop edge. The mechanism is similar to the inductive charging often seen on phones nowadays, but at higher frequency and larger scale, enabling power to be transmitted several feet (at least a meter) above the desktop.

The range is impressive (this isn’t the maximum), but the efficiency is not advertised.

The kit from ETI contained several PCB-coil receivers, which [Matt] built into a number of devices, including a lamp, heated cup, microphone, speakers, his mouse, keyboard, and even a custom base to run his monitor, which really shows the power these things can pull.

The microphone is a non-Bluetooth RF unit lovingly modified to studio quality, at least as far as we can tell on laptop speakers through YouTube’s compression. The speakers use a pair of Bluetooth modules to negotiate stereo sound while staying in sync. And before you ask “what about signal for the monitor?”– we have to inform you that was taken care of too, via a wireless HDMI dongle. Check it out in the video below.

Of course the elephant in the room here is power usage — there’s a 10 W base draw, and probably a big hit to efficiency vs cabled-everything– but we figure he gets partway to a pass on that by using a Frameworks mainboard instead desktop hardware. Indeed, a full analysis might show that the transmission efficiency of this system is no worse than the power to charge/discharge inefficiencies in a more conventional battery powered wireless setup.

While no wires is pretty clean, we’re not sure this beats the totally-hidden-in-the-desk PC [Matt] built last year in terms of minimalist aesthetic.  That Frameworks mainboard also likely lacks the power of his triple-screen luggable, but this was still an entertaining build.

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Let’s Buy Commodore! Well, Somebody Is.

June 7, 2025 by 61 Comments

When a man wearing an Atari T-shirt tells you he’s buying Commodore it sounds like the plot for an improbable 1980s movie in which Nolan Bushnell and Jack Tramiel do battle before a neon synthwave sunset to a pulsating chiptune soundtrack. But here on the screen there’s that guy doing just that, It’s [Retro Recipes], and in the video below he’s assembling a licensing deal for the Commodore brand portfolio from the distant descendant of the Commodore of old.

It’s a fascinating story and we commend him for tracing a path through the mess that unfolded for Commodore in the 1990s. We tried the same research path with a friend a few years ago and ended up with an anonymous Dutch paper company that wouldn’t answer our calls, so we’re impressed. In conjunction with several other players in the Commodore retrocomputing world he’s trying to assemble a favourable percentage deal for manufacturers of new parts, computers, and other goodies, and we’re pleased to see that it’s for the smaller player as much as for the industry giant.

When looking at a story like this though, it’s important not to let your view become clouded by those rose tinted glasses. While it’s great that we’re likely to see a bunch of new Commodore-branded Commodore 64s and parts, there are many pitfalls in taking it beyond that. We’ve seen the Commodore logo on too many regrettable licensed products in the past, and we fear it might be too tempting for it to end up on yet another disappointing all-in-one video game or just another budget PC. If something new comes out under the Commodore brand we’d like it to be really special, exploiting new ground in the way the Amiga did back in the day. We can hope, because the alternative has dragged other famous brands through the mud in recent years.

If you want an insight into the roots of the original Commodore’s demise, have a read of our Hackaday colleague [Bil Herd]’s autobiography.

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