Your ESP32 As A USB Bluetooth Dongle

Using Bluetooth on a desktop computer is now such a seamless process; it’s something built-in and just works. Behind that ubiquity is a protocol layer called HCI, or Host Controller Interface, a set of commands allowing a host computer to talk to a Bluetooth interface.  That interface doesn’t have to be special, and [Dakhnod] is here to show us that it can be done with an ESP32 microcontroller through its USB interface.

The linked repository doesn’t tell us which of the ESP32 variants it works with, but since not all of them have a USB peripheral we’re guessing one of the newer variety. It works with Linux computers, and we’re told it should work with Windows too if a HCI driver is present. We might ask ourselves why such a project is necessary given the ubiquity of Bluetooth interfaces, but for us it’s provided the impetus to read up on how it all works.

We can’t find anyone else in our archive who’s made a Bluetooth dongle in this way, but we’ve certainly seen sniffing of HCI commands to reverse engineer a speaker’s communications.

The Last Instrument To Get Auto-Tuned

Various decades have their musical signature, like the excessive use of synthesizers and hairspray in the 1980s pop music scene. Likewise, the early 2010s was marked by a fairly extreme use of autotune, a technology that allows sounds, especially vocals, to be shifted to precise pitches regardless of the pitch of the original source. In this dark era, a wide swath of instruments and voices on the charts were auto-tuned at some point, although we don’t remember this iconic instrument ever being featured among the annals of pitch-shifted pop music.

The auto-tuned kazoo created by [Guy Dupont] does its pitch corrections on-the-fly thanks to a built-in ESP-32-S3 microcontroller which, through a microphone inside the kazoo, listens for note of the musician’s hum and corrects it to the closest correctly pitched note. Once it identifies the note it outputs a kazoo-like pitch-corrected note from a small speaker, also hidden inside the instrument. It does this fast enough for live performances using the YIN fundamental frequency estimation algorithm. Not only can the kazoo be played directly, but thanks to the implementation of MIDI it can be used to control other synthesizers or be played through other means as a stand-alone synthesizer.

Much like the 80s, where the use of synthesizers relaxed from excessive use on nearly every instrument on every track throughout the decade to a more restrained use as the decade faded, so has autotune been toned down in most music to be more subtly applied. But like our enjoyment of heavily synthesized tunes outside the 80s like those by Daft Punk or The Weeknd, we can also appreciate something heavily auto-tuned outside of the 2010s like a stylized kazoo or a T-Pain-style guitar effects pedal.

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A fast-looking hand plays a reaction time game.

2024 Tiny Games Challenge: Improving Reaction Time

What lies at the heart of many games? In a sense, it’s your response time, which is a function of hand-eye coordination. Although the 2024 Business Card Challenge has come to a close, [gokux] tends to go small anyway, and has taken their miniature approach to the Tiny Games Challenge with this awesome little reaction time game.

It’s basically whack-a-mole, but instead of striking down fuzzy puppets, you get fast and furious on big buttons that light up. Press any button to start, and there is a 3-2-1 countdown to get you geared up for action. Once the screen says ‘GO’, you’re off to the races. Each of the four buttons will light up in random order, and your overall response time is taken as the average of these four.

While there are many microcontrollers that would work here, [gokux] chose the Seeed Studio Xiao ESP32-C3. If you want to make one of these for yourself, there are excellent build instructions waiting for you. Be sure to check it out in action after the break. Oh, and be sure to let [gokux] know if you can beat 220 ms.

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Photoresistor-based Single Pixel Camera

[Hugh] has been going back through episodes of the Hackaday podcast, and Elliot mentioned in episode 67 that it can often be inspiring to go back through the archives of Hackaday to find ideas for new projects. Well, he did just that and came across a single-pixel camera made using an infrared photodiode. He decided to try and hack together his own single-pixel camera, but this time on the cheap and using an ever simpler component – a photoresistor!

His description of the project tickled me – “I’ve used an ESP32, MicroPython, two servos, a peanut butter jar lid, a toilet paper roll, a paper towel roll, magnets and scrap wood for this version.” That’s certainly a much simpler bill of materials than the original (which was written up by Hackaday way back in 2015), which used a nice metal frame to hold everything together. However, there’s absolutely nothing wrong with improvising with things you happen to have to hand.

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2024 Business Card Challenge: CardTunes Bluetooth Speaker

A business card form factor can be quite limiting, but that didn’t stop [Schwimmflugel] from creating CardTunes, an ESP32-based Bluetooth audio speaker that tried something innovative to deliver the output.

What’s very interesting about this design is the speaker itself. [Schwimmflugel] aimed to create a speaker out of two coils made from flexible circuit board material, driving them with opposite polarities to create a thin speaker without the need for a permanent magnet.

The concept is sound, but in practice, performance was poor. One could identify the song being played, but only if holding the speaker up to one’s ear. The output was improved considerably with the addition of a small permanent magnet behind the card, but of course this compromised the original vision.

Even though the concept of making a speaker from two flexible PCB panel coils had only mixed success, we love seeing this kind of effort and there’s a lot to learn from the results. Not to mention that it’s frankly fantastic to even have a Bluetooth speaker on a business card in the first place.

The 2024 Business Card Challenge is over, but judging by all the incredible entries we received, we’re thinking it probably won’t be too long before we come up with another sized-constrained challenge.

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A bunch of unpopulated PCB business cards with rad dead rat artwork.

2024 Business Card Challenge: A Very Annoying Business Card, Indeed

Usually the business card itself is the reminder to get in contact with whoever gave it to you. But this is Hackaday, after all. This solar-powered card reminds the recipient to send [Dead Rat Productions] an email by beeping about every two hours, although the gist of that email may simply be begging them to make it stop, provided they didn’t just toss the thing in the garbage.

The full-on, working version of the card is not intended for everyone — mostly serious-looking A-list types that ooze wealth. Most of [Dead Rat Productions]’ pub mates will get an unpopulated version, which could be a fun afternoon for the right kind of recipient, of course.

That person would need a Seeed Studio Xiao SAMD21, a solar panel, plus some other components, like an energy-harvesting chip to keep the battery topped up. Of note, there is a coin cell holder that requires prying with a screwdriver to get the battery out, so there’s really no escaping the beeping without some work on their part. We rather like the artwork on this one, especially the fact that the coin cell sits inside the rat’s stomach. That’s a nice touch.

Swapping Vinyl For Cardboard With This ESP32 Turntable

Cardboard is a surprisingly durable material, especially in its corrugated form. It’s extremely lightweight for its strength, is easy to work, can be folded and formed into almost any shape, is incredibly inexpensive, and when it has done its duty it can be recycled back into more paper. For these reasons, it’s often used in packaging material but it can be used to build all kinds of things outside of ensuring that products arrive at their locations safely. This working cardboard record player is one example.

While the turntable doesn’t have working records in the sense that the music is etched into them like vinyl, each has its own RFID chip embedded that allows the ESP32 in the turntable’s body to identify them. Each record corresponds to a song stored on an SD card that instructs the ESP32 to play the appropriate song. It also takes care of spinning the record itself with a small stepper motor. There are a few other details on this build that tie it together too, including a movable needle arm held on with a magnet and a volume slider.

As far as a building material goes, cardboard is fairly underrated in our opinion. Besides small projects like this turntable, we’ve also seen it work as the foundation for a computer, and it even has the strength and durability to be built into a wall or even used as shelving material. And, of course, it’s a great material to use when prototyping new designs.

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