The PT2399 Delay/Echo Chip Data Sheet You Never Had

If you are fortunate enough to have had the opportunity to play with an analogue-reel-to-reel tape recorder in a well-equipped studio, you probably looped the tape around to create an echo, or a delay in the audio. It was a desirable effect to have, but not a practical one for a guitar pedal or similar portable accessory. Silicon alternatives for creating delays have been in production since the 1960s, first the so-called bucket brigade delay lines that used a switched chain of on-chip capacitors, and more recently all-digital chips that process the delay by storing samples in RAM. One of the more popular of those is the Princeton Technology PT2399, but it comes with something of a snag for the experimenter in the form of a sparse data sheet. Thankfully the folks at [Electrosmash] have come to the rescue on that front with a thorough technical examination of the chip that should fill in any gaps in the official documentation.

After a brief examination of the range of chips of which the 2399 is a part, they dive right into the chip’s internals by rearranging the internal circuit diagram from the data sheet to the point at which it makes more sense. At which point the difference between the chip’s delay and echo functions becomes obvious, through the inclusion of a feedback path.

We then are taken through the pins, examining what lies behind the power supply and analog inputs and outputs. We are somewhere between a data sheet and an app note here, as some of this is information rarely present even in really good data sheets. Finally, we are taken through the chip’s performance, with real-world distortion and noise measurements. Armed with this page, the would-be PT2399 designer really can say they know what they are working with.

Surprisingly few PT2399s have appeared on these pages, however one did pop up in the Synthbike.

Cloning the Echo Show With a Fabric Wrapped Pi

After seeing an Echo Show in the flesh plastic, [anonteapot] was inspired to create his own take on Amazon’s latest on-ramp to their ecosystem. He had the Raspberry Pi and a touch screen, but not much else. He doesn’t even have a dedicated work area at home, much less something as exotic as a 3D printer to run off a custom case. For this decidedly low-tech build, all that was required tool-wise was a razor blade knife and a screwdriver.

The majority of the device, which he refers to as the PiShow, is made of hand-cut pieces of MDF. In fact, the whole build relied on his ability to neatly cut pieces of MDF with hand tools on his bedroom floor. We wouldn’t suggest such a setup as a general rule, but respect for pushing ahead without so much as a table to work on.

To connect the pieces of MDF, he used angle brackets from the hardware store. These were originally 90 degrees, but he bent them by hand to achieve the angles seen in the final device. He notes that there was no specific angles he was aiming for when putting the box together; he simply wanted something that looked cool and was large enough internally to hold his electronics.

Covering the PiShow is some jersey material that [anonteapot] bought at a local fabric store. It has a little stretch to it so he was able to pull it tight over the MDF frame and keep the wrinkles out. As a general rule we don’t see many projects here at Hackaday that are wrapped in fabric, but we’ve got to admit, it makes for a nice final look.

The trickiest part of the build ended up being the side panels. While the rest of the frame was relatively simple, the sides needed to precisely conform to some fairly complex geometry. Luckily the side panels aren’t actually holding any weight, so he decided to just cut them out of cardboard. There’s a bit of a gap at the top, but he’s going to try and rectify that with a visit from his glue gun soon.

Internally things are sort of just hanging around inside the case, but since this device is never going to move off of the nightstand, it probably doesn’t need to be terribly secure. In truth, getting all the hardware mounted up cleanly with the construction methods available to [anonteapot] would have been a bit tricky anyway.

This is the first time we’ve seen somebody take a swing at replicating the Echo Show, usually we just see people trying to cram the Echo Dot into something else. If the software side is more your thing, be sure to check out this excellent guide on Alexa Skills development by our very own [Al Williams].

The Amazon Echo As A Listening Device

It is an inevitability that following swiftly on the heels of the release of a new device there will be an announcement of its rooting, reverse engineering, or other revealing of its hackability. Now the device in question is the Amazon Echo, as MWR Labs announce their work in persuading an Echo to yield the live audio from the microphone and turn the voice assistant device into a covert listening device.

The work hinges on a previous discovery and reverse engineering (PDF) of Amazon’s debug connector on the base of the Echo, which exposes both an SD card interface and a serial terminal. Following that work, they were able to gain root access to the device, analyze the structure of the audio buffers and how the different Echo processes use them, and run Amazon’s own “shmbuf_tool” application to pipe raw audio data to a network stream. Astoundingly this could be done without compromising the normal operation of the device.

It should be stressed, that this is an exploit that requires physical access to the device and a bit of knowledge to perform. But it’s not inconceivable that it could be made into a near-automated process requiring only a device with a set of pogo pins to be mated with an Echo that has had its cover quickly removed.

That said, inevitably there will be enough unused Echos floating around before too long that their rootability will make them useful to people in our community. We look forward to what interesting projects people come up with using rooted Echos.

This isn’t the first time we’ve covered the use of an Echo as a listening device.

Via Hacker News.

Amazon Echo image: FASTILY [CC BY-SA 4.0].

Alexa, Sudo Read My Resistor! A Challenge for Hackers

Nothing makes us feel more like we’re on Star Trek then saying “Computer, turn on desk light,” and watching the light turn on. Of course, normal people would have left the wake up word as “Alexa,” but we like “Computer” even if it does make it hard to watch Star Trek episodes without the home automation going crazy.

There’s a lot of hype right now about how voice recognition and artificial intelligence (AI) are transforming everything. We’ve even seen a few high-profile types warning that AI is going to come alive and put us in the matrix or something. That gets a lot of press, but we’re not sure we are even close to that, yet. Alexa and Google’s similar offerings are cool, there’s no doubt about it. The speech recognition is pretty good, although far from perfect. But the AI is really far off still.

Today’s devices utilize two rather rudimentary parts to provide an interaction with users. The first is how the devices pattern match language; it isn’t all that sophisticated. The other is the trivial nature of many of the apps, or — as Alexa calls them — skills. There are some good ones to be sure, but for every one useful application of the technology, there’s a dozen that are just text-to-speech of an RSS feed. Looking through the skills available we were amused at how many different offerings convert resistor color codes back and forth to values.

There was a time when building electronics meant learning the resistor color code. With today’s emphasis on surface mount components, though, it is less useful than it used to be. Still, like flossing, you really ought to do it. However, if you have an Amazon Alexa, it can learn the color code for you thanks to [Dennis Mantz].

Don’t have an Alexa? You can still try it in your browser, as we will show you shortly. There are at least eight similar skills out there like this one from [Steve Jernigan] or [Andrew Bergstrom’s] Resistor Reader.

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That’s No Moon! That’s a Virtual Assistant

[Wisecracker] likes how the Amazon Echo Dot works, but he doesn’t like how they sound or how they resemble hockey pucks. A little 3D printing, though, and he transformed the Dot into a credible Death Star. That doesn’t sound very friendly, we guess, so he calls it Alex-Star.

What makes it work is the Death Star’s “superlaser” — the weapon operated by a console that looks suspiciously like some studio video equipment — happens to be about the size and shape of a two-inch speaker. [Wisecracker] added a slot to let the sound out of the second speaker. You can see the thing in action in the video below.

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Controlling a Game Room with Amazon Echo

If there are two things we love here at Hackaday, it’s games and automating mundane tasks by adding a lot of electronics and voice control. A game room is, therefore, the perfect sandbox for projects that get us excited in all of the right ways. Liberty Games, a UK-based games room company, already had a really impressive game room (as you might expect). They’ve just posted an awesome build log showcasing how they went about automating mundane game room tasks by adding a lot of electronics and voice control.

There were four tasks that Liberty Games wanted to be able to complete with voice control: releasing billiards balls on their pool table, adding credits to an arcade machine, releasing pinballs on a pinball machine, and control of a CD jukebox. For all of these tasks, they used an Amazon Echo, which already has built-in support for adding new “skills” (Amazon’s term for user-created Alexa commands). These skills allow the Echo to communicate with other devices using JavaScript Object Notation (JSON).

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Retrofitting a Vintage Intercom to Run Amazon Alexa

The Amazon Echo is a pretty cool piece of tech: it lets you ask questions, queue up music, find out the weather, and more, without having to do anything but talk. But, the device itself is a bit pricey, and looks a little boring. What if you could have all the features of the Echo, but in a cool retro case and at a cheaper price?

Well, you can, and that’s exactly what [nick.r.brewer] did, using a ’50s intercom and a Raspberry Pi. He picked the vintage intercom up at an antique store for $20, and the Raspberry Pi Zero is less than $10. So, for about $30 (and some parts most of us have lying around) he was able to build a cool looking device with all of the capabilities of the Amazon Echo.

The hardware portion of the build was pretty straightforward, with the Raspberry Pi, a sound card, WiFi dongle, USB hub, and microphone all fitting nicely inside the case of the intercom. The software side of things is a little more tricky, but with a device like this it runs well with Amazon’s Alexa SDK. Of course, if you want to add more hardware features, that’s possible too.

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