Uncovering The Echo Dot’s Hidden USB Port

If you upgraded to Amazon’s latest Echo Dot, you might have been surprised to find that the diminutive voice assistant had shed its USB port. Earlier models of the Dot used a garden variety micro USB port for power, which hackers eventually figured out also provided a helpful way to snoop around inside the device’s firmware. The fact that the USB port was deleted on the latest Echo Dot in favor of a simple barrel connector for power was seen by some as a sign that Amazon was trying to keep curious owners out of their hardware.

But as [Brian Dorey] shows, all they did was put a bump in the road. While they removed the external USB connector, the traces for it are still on the board waiting to be accessed. Even better, it turns out the USB data lines are connected to the test points located on the bottom of the Dot. All you need is a simple breakout that will connect through the existing opening in the device’s case, and you’ve got your USB port back.

So what can you do with USB on the Echo Dot? Well, not much right now. [Brian] found that the Dot shows up as a Mediatek device under Linux using lsusb, and fastboot can see it and even confirms the presence of a locked bootloader. It’s going to take some work from the community to see how deep this particular rabbit hole goes.

Even if you’re not interested in restoring its USB port, [Brian] has uncovered a wealth of fascinating hardware information about the Echo Dot during his deep-dive. He’s mapped out many of the test points located throughout the device’s PCBs, and found a few interesting points that might be worth further investigation. For example, he found that driving one of the pins high would trigger the Dot to mute its microphones; which could be useful for anyone looking to cover Alexa’s ears.

[Brian] first cracked open the Echo Dot last month, after scoring one for cheap during Amazon’s Prime Day sale. It looks like he’s making fairly rapid progress on unraveling the mysteries of this popular gadget, and we’re very interested in seeing where this research takes us.

DIY PC Test Bench Puts Hardware Troubleshooting Out In The Open

If you’ve built a few PCs, you know how frustrating troubleshooting can be. Finding a faulty component inside the cramped confines of a case can be painful — whether its literal when sharp edges draw blood, or just figurative when you have to open that cramped case multiple times to make adjustments.

[Colonel Camp] decided to make life a bit easier by building this PC test bench which makes component troubleshooting much easier and can be built with old parts you probably have lying around. [Camp] was inspired by an old Linus PC Tech Tips video on the same topic. The key to the build is an old PC case. These cases are often riveted together, s a drill makes quick work of disassembling the chassis to easily get to all of the components. The motherboard pan and rear panel/card cage become the top shelf of the test bench, while the outer shell of the case becomes the base and a storage area. Two pieces of lumber support the upper shelf. The build was primed and painted with several coats of grey.

[Camp] built up his testbench with a modest motherboard, cooler and a 970 video card. He loaded up Manjaro Linux to verify everything worked. The basic hardware has already been replaced with a new system including a ridiculously huge cooler. But that’s all in a day’s work for a test bench PC.

We’ve seen some wild workbenches over the years, and this one fits right in for all your PC projects. Check out the video after the break!

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Switching Over To SMPS For Efficiency

[Hesam Moshiri] has built a variable switch-mode power supply over on hackaday.io. When prototyping a new circuit, often the goal is to get a proof-of-concept working as soon as possible to iron out all of the bugs it might have. The power supply can easily be an afterthought, and for smaller projects we might just reach for an adjustable LM317 voltage regulator to dial in the correct voltage and then move on with the meat of the project. These linear regulators are incredibly inefficient though, so if you find yourself prototyping with one of these often enough, it might be worthwhile to switch to something better.

While it’s easy to simply buy a switch-mode power supply (SMPS) that has everything you need, and rated for 90% or higher efficiency at the same time, getting one with an adjustable output isn’t as easy. This one is based on the relatively popular LM2576-Adj chip which handles the switching frequency part of the circuit automatically. You will also need some large capacitors, an inductor (one of the disadvantages of an SMPS circuit) and a small potentiometer to use as the feedback control for the LM2576. This special pin allows the output voltage of the SMPS to be precisely controlled.

Granted, this project might not be breaking any new grounds, but if you’ve never given serious thought to your small breadboard circuit power supplies, it’s definitely worth looking into. An improvement from a linear regulator’s 30% efficiency to 90% efficiency from an SMPS will not only save you a ton of energy but also solve a lot of heat dissipation problems. If you don’t want to build a switch-mode supply 100% from scratch, though, it might also be possible to modify an existing one to suit your needs as well.

Taking A Peek Inside Amazon’s Latest Dot

Like a million or so other people, [Brian Dorey] picked up a third generation Echo Dot during Amazon’s big sale a couple weeks ago. Going for less than half its normal retail price, he figured it was the perfect time to explore Amazon’s voice assistant offerings. But the low price also meant that he didn’t feel so bad tearing into the thing for our viewing pleasure.

By pretty much all accounts, the Echo Dot line has been a pretty solid performer as far as corporate subsidized home espionage devices go. They’re small, fairly cheap, and offer the baseline functionality that most people expect. While there was nothing precisely wrong with the earlier versions of the Dot, Amazon has used this latest revision of the device to give the gadget a more “premium” look and feel. They’ve also tried to squeeze a bit better audio out of the roughly hockey puck sized device. But of course, some undocumented changes managed to sneak in there as well.

For one thing, the latest version of the Dot deletes the USB port. Hackers had used the USB port on earlier versions of the hardware to try and gain access to the Android (or at least, Amazon’s flavor of Android) operating system hiding inside, so that’s an unfortunate development. On the flip side, [Brian] reports there’s some type of debug header on the bottom of the device. A similar feature allowed hackers to gain access to some of Amazon’s other voice assistants, so we’d recommend hopeful optimism until told otherwise.

The Echo Dot is powered by a quad-core Mediatek MT8516BAAA 64-bit ARM Cortex-A35 processor and the OS lives on an 8GB Samsung KMFN60012M-B214 eMMC. A pair of Texas Instruments LV320ADC3101 ADCs are used to process the incoming audio from the four microphones arranged around the edge of the PCB, and [Brian] says there appears to be a Fairchild 74LCX74 flip-flop in place to cut the audio feed when the user wants a bit of privacy.

Of course, the biggest change is on the outside. The new Dot is much larger than the previous versions, which means all the awesome enclosures we’ve seen for its predecessor will need to be reworked if they want to be compatible with Amazon’s latest and greatest.

A New KiCAD Tutorial Hits The Scene

KiCAD has a rightfully earned image problem regarding beginners. The shiny new version 5 has improved things (and we’re very excited for v6!) but the tool is a bit obtuse even when coming from a electronics design background, so we’re always excited to see new learning material. [Mike Watts] is the latest to join the esteemed group of people willing to export their knowledge with his KiCAD tutorial series on GitHub that takes the aspiring user from schematic through fab and assembly.

The tutorial is focused around the process of creating a development board for the dimuitive Microchip née Atmel ATSAMD10 Cortex M0 ARM CPU. It opens by asking the reader to create a schematic and proceeds to teach by directing them to perform certain actions then explaining what’s going on and which shortcuts can accelerate things. This method continues through layout, manufacturing, and assembly.

Of note is that when defining the board outline [Mike] describes how to use OpenSCAD to parametrically define it; a neat micro-tutorial on using the two great tools to compliment each other. We also love that upon successful completion of the tutorial series the user will have developed a tiny but useful development board that can be assembled for about $3 in single quantities!

As with all open source work, if you have quibbles or want to contribute open a pull request and give [Mike] a hand!

High Precision Analog IO With Digital Pins

Reading the temperature of your environment is pretty easy right? A quick search suggests the utterly ubiquitous DHT11, which speaks a well documented protocol and has libraries for every conceivable microcontroller and platform. Plug that into your Arduino and boom, temperature (and humidity!) readings. But the simple solution doesn’t hit every need, sometimes things need to get more esoteric.

The technique summarized by an image from Microchip Appnote AN685

For years we’ve been watching [Edward]’s heroic efforts to build accessible underwater sensing hardware. When we last heard from him he was working on improving the accuracy of his Arduino’s measurements of the humble NTC thermistor. Now the goal is the same but he has an even more surprising plan, throw the ADC out entirely and sample an analog thermistor using digital IO. It’s actually a pretty simple trick based on an intuitive observation, that microcontrollers are better at measuring time than voltage. 

The basic circuit

The circuit has a minimum of four components: a reference resistor, the thermistor, and a small capacitor with discharge resistor. To sense you configure a timer to count, and an edge interrupt to capture the value in the timer when its input toggles. One sensing cycle consists of discharging the cap through the discharge resistor, enabling the timer and interrupt, then charging it through the value to measure. The value captured from the timer will be correlated to how long it took the cap to charge above the logic-high threshold when the interrupt triggers. By comparing the time to charge through the reference against the time to charge through the thermistor you can calculate their relative resistance. And by performing a few calibration cycles at different temperatures ([Edward] suggests at least 10 degrees apart) you can anchor the measurement system to real temperature.

For all the gory details, including tips for how to save every last joule of energy, check out [Edward]’s post and the Microchip appnote AN685 he references. Besides this series [Edward]’s Cave Pearl Project has already yielded an impressive number of Hackday posts. For more great hardware writeups check out a general hardware build for a single sensing node, or the “temperature sensor” [Edward] made with no external parts at all!

A Microwave Kiln, From Scratch

We are normally told that microwave ovens are strictly for food only, and that anything else will cause all sorts of bad things to come our way. There can be few readers who haven’t at some time seen the shower of sparks when an inadvertent metallic object finds its way onto the turntable.

A particularly useful non-food application for a microwave oven comes in the form of the small kilns sold for glass fusing. These are ceramic cylinders coated internally with silicon carbide, and [ShakeTheFuture] shows us how to make your own.

Key to the process is ceramic fibre insulation, which is bonded both to itself and to the fused silicon carbide grit by a cured solution of waterglass, sodium silicate. The result can easily reach the required temperature for fusing glass, but also has an application in burning out surplus wax or PLA from a plaster mould. It’s particularly interesting to see the technique with the waterglass in action, and you can see a run-down of the whole thing in the video below the break.

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