Be Wary Of Flash-less ESP32-C3 Super Mini Boards

December 23, 2025 by Maya Posch 6 Comments

Everyone loves tiny microcontroller boards, and the ESP32-C3 Super Mini boards are no exception. Unfortunately if you just casually stroll over to your nearest online purveyor of such goods to purchase a bunch of them, you’re likely to be disappointed. The reason for this is, as explained in a video by [Hacker University] that these boards are equipped with any of the variants of the ESP32-C3. The worst offender here is probably the version with the ESP32-C3 without further markings, as this one has no built-in Flash for program storage.

Beyond that basic MCU version we can see the other versions clearly listed in the Espressif ESP32-C3 datasheet. Of these, the FN4 is already listed as EOL, the FH4AZ as NRND, leaving only the FH4 and FH4X with the latter as ‘recommended’ as the newest chip revision. Here the F stands for built-in Flash with the next character for its temperature rating, e.g. H for ‘High’. Next is the amount of Flash in MB, so always 4 MB for all but the Flash-less variant.

Identifying this information from some online listing is anything but easy unless the seller is especially forthcoming. The chip markings show this information on the third row, as can be seen in the top image, but relying solely on a listing’s photos is rather sketchy. If you do end up with a Flash-less variant, you can still wire up an external Flash chip yourself, but obviously this is probably not the intended use case.

As always, caveat emptor.

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ESP32 Hosts Functional Minecraft Server

September 13, 2025 by Tyler August 11 Comments

If you haven’t heard of Minecraft, well, we hope you enjoyed your rip-van-winkle nap this past decade or so. For everyone else, you probably at least know that this is a multiplayer, open world game, you may have heard that running a Minecraft server is a good job for maxing out a spare a Raspberry Pi. Which is why we’re hugely impressed that [PortalRunner] managed to squeeze an open world onto an ESP32-C3.

Of course, the trick here is that the MCU isn’t actually running the game — it’s running bareiron, [PortalRunner]’s own C-based Minecraft server implementation. Rewriting the server code in C allows it to be optimized for the ESP32’s hardware, but it also let [PortalRunner] strip his server down to the bare essentials, and tweak everything for performance. For example, instead of the multiple octaves of Perlin noise for terrain generation, with every chunk going into RAM, he’s using the x and z of the corners as seeds for the psudorandom rand() function, and interpolating between them. Instead of caves being generated by a separate algorithm, and stored in memory, in bareiron the underground is just a mirror-image of the world above. Biomes are just tiled, and sit separately from one another.

So yes, what you get from bareiron is simpler than a traditional Minecraft world — items are simplified, crafting is simplified, everything is simplified, but it’s also running on an ESP32, so you’ve got to give it a pass. With 200 ms to load each chunk, it’s playable, but the World’s Smallest Minecraft Server is a bit like a dancing bear: it’s not about how well it dances, but that it dances at all.

This isn’t the first time we’ve seen Minecraft’s server code re-written: some masochist did it in COBOL, but at least that ran on an actual computer, not a microcontroller. Speaking of low performance, you can’t play Minecraft on an SNES, but you can hide the game inside a cartridge, which is almost as good.

Thanks to [CodeAsm] for the tip. Please refer any other dancing bears spotted in the wild to our tips line.

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A clear acrylic cylinder is shown, inside of which plants are visible. There is mist inside the tube, and LEDs light it from above. A black plastic cap to the tube is visible.

Preserve Your Plants With An Automated Terrarium

June 30, 2025 by Aaron Beckendorf 1 Comment

For those of us who aren’t blessed with a green thumb and who are perhaps a bit forgetful, plants can be surprisingly difficult to keep alive. In those cases, some kind of automation, such as [Justin Buchanan]’s Oasis smart terrarium, is a good way to keep our plants from suffering too much.

The Oasis has an ultrasonic mister to water the plants from a built-in tank, LED grow lights, fans to control airflow, and a temperature and humidity sensor. It connects to the local WiFi network and can set up recurring watering and lighting schedules based on network time. Most of the terrarium is 3D-printed, with a section of acrylic tubing providing the clear walls. Before installing the electronics, it’s a good idea to waterproof the printed parts with low-viscosity epoxy, particularly since the water tank is located at the top of the terrarium, where a leak would drip directly onto the control electronics.

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Simple Antenna Makes For Better ESP32-C3 WiFi

April 7, 2025 by Dan Maloney 46 Comments

We’ve seen tons of projects lately using the ESP32-C3, and for good reason. The microcontroller has a lot to offer, and the current crop of tiny dev boards sporting it make adding a lot of compute power to even the smallest projects dead easy. Not so nice, though, is the poor WiFi performance of some of these boards, which [Peter Neufeld] addresses with this quick and easy antenna.

There are currently a lot of variations of the ESP32-C3 out there, sometimes available for a buck a piece from the usual suspects. Designs vary, but a lot of them seem to sport a CA-C03 ceramic chip antenna at one end of the board to save space. Unfortunately, the lack of free space around the antenna makes for poor RF performance. [Peter]’s solution is a simple antenna made from a 31-mm length of silver wire. One end of the wire is formed into a loop by wrapping it around a 5-mm drill bit and bending it perpendicular to the remaining tail. The loop is then opened up a bit so it can bridge the length of the ceramic chip antenna and then soldered across it. That’s all it takes to vastly improve performance as measured by [Peter]’s custom RSSI logger — anywhere from 6 to 10 dBm better. You don’t even need to remove the OEM antenna.

The video below, by [Circuit Helper], picks up on [Peter]’s work and puts several antenna variants to further testing. He gets similarly dramatic results, with 20 dBm improvement in some cases. He does note that the size of the antenna can be a detriment to a project that needs a really compact MCU and tries coiling up the antenna, with limited success. He also did a little testing to come up with an optimal length of 34 mm for the main element of the antenna.

There seems to be a lot of room for experimentation here. We wonder how mounting the antenna with the loop perpendicular to the board and the main element sticking out lengthwise would work. We’d love to hear about your experiments, so make sure to ping us with your findings.

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A light-up clock displays the day of the week.

What Day Is It Again? Check The Clock

January 22, 2025 by Kristina Panos 7 Comments

If you’re lucky enough to work from home, you’ll soon find that it presents its own set of challenges, mostly related to work/life balance. It can get so bad that you don’t know what day of the week it is. Really. Ask us how we know.

Rather than miss a meeting (or a day off), prolific hacker [Arnov Sharma] created this day of the week clock. It uses a customized LED driver board with seven sets of three LEDs, each driven by a MOSFET. Each MOSFET is controlled by a DFRobot Mini Beetle ESP32-C3. It runs on a 2200 mAh, 3.7 V lithium-ion battery.

While this is mostly PCBs, there are three printed parts that turn it into a displayable object. We really like the look of this clock — it has just the right amount of pizazz to it and reminds us of a and old movie marquee. Be sure to check out the great build instructions.

We love a good clock around here. In case you missed it, here is the latest from [Moritz v. Sivers] that uses a caustic lens to display the time.

A small mood/busy indicator attached to a laptop.

Personal Traffic Light Stops Them In Their Tracks

December 14, 2024 by Kristina Panos 30 Comments

Working from home can be pretty cool, but if you’re not the only one in the house trying to do it, the whole situation can feel like you’re right back in the office with all those walking, talking distractions. Except they’re in pajamas instead of business casual.

So, what’s the answer? Many times it’s not practical to stop what you’re doing, especially just to communicate that you’re busy. We suppose you could glare at them, put up your hand, or even give a dismissive wave, but a better solution might be this mood signal built by [gokux].

Through a simple web app, you can be red to indicate that you’re super busy, yellow to mean busy-ish, and green for let’s gossip about the cats.

This mood indicator is built on the Seeed Xiao ESP32-C3 and shows the given mood indicator on a small matrix of sixteen WS2812B LEDs. It’s powered by a 600 mAh, 3.7 V battery and a small push button switch. As usual, [gokux] has grade-A instructions for building your own version of this slick solution.

Would you like something more tactile and low-tech? Check out our own [Bob Baddeley]’s free/busy indicator from the lockdown days.

Little Quadruped Has PCB Spine And No Wiring

October 29, 2024 by Danie Conradie 10 Comments

Dealing with all the wiring can quickly become a challenge on robots, especially the walking variety which have actuators everywhere. [Eric Yufeng Wu] sidestepped the wiring issue by creating Q8bot, a little quadruped where all the components, including the actuators, are mounted directly on the PCB.

[Eric] uses a custom PCB as the spine of the robot, and the eight servos plug directly into connectors on the PCB. With their bottom covers removed, the servos screw neatly into a pair of 3D printed frames on either side of the PCB, which also have integrated 14500 battery holders. The PCB is minimalist, with just the XIAO ESP32C3 module, a boost converter circuit to drive the servos, and a battery fuel gauge. Each SCARA-style leg consists of four SLS 3D printed segments, with press-fit bearings in the joints.

The little one moves quickly, and can even do little jumps. For this prototype, most of the control processing is done on a laptop, which sends raw joint angles to the onboard ESP32 via the ESP-Now protocol. We think this little robot has a lot of development potential, and fortunately [Eric] has made all the hardware and software files available for others to build their own.

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