My Custom USB Hub: 2x USB-A, 2x USB-C

My Custom USB Hub: 2x USB-A, 2x USB-C

I’ve got a regular desk setup. There’s a monitor on it. All good — except plugging in USB devices is a pain. The USB-A (old) ports are placed on the bottom edge, so every time I need to connect something, I play the classic game of “flip the plug the right way by feel.” And if it’s a USB-C device — it has to go directly into the laptop, since that’s the only place with the right port.
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USB Power Meter

USB Power Meter

Casually put together a small but rather fun project. I got curious about how much power my DIY gadgets actually consume—and at the same time, I wanted to check the real capacity of those AliExpress batteries. Sure, you could use a multimeter, but then you’d have to rig up some janky setup to wedge it into a USB cable, plus keep unplugging it whenever you need it elsewhere. And devices with microcontrollers have fluctuating power draw depending on their operating mode. So I built myself a dedicated device.
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Comparing MH-Z19B and SCD41: Building a Smarter CO₂ Monitor

Comparing MH-Z19B and SCD41: Building a Smarter CO₂ Monitor

A small device based on the MH-Z19B sensor has been sitting on my desk for years, quietly reminding me when it’s time to open a window and let some fresh air in. Its design is… well, not exactly elegant, but the utility more than makes up for any aesthetic shortcomings.
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Custom FM Receiver with STM32 and RDA5807: Full Project Breakdown

Custom FM Receiver with STM32 and RDA5807: Full Project Breakdown

I built an FM radio receiver. As usual, the goal was to “build something useful and learn something new along the way.” What made this project especially exciting was that it involved working with an STM32 microcontroller—something I hadn’t done before, even though I’ve had several dev boards and programmers lying around for years. I also really wanted to use the headphone wire as the antenna, just like in commercial devices.
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Low-Power LCD Clock with ESP32-C3 and Custom HT1621 Driver

Low-Power LCD Clock with ESP32-C3 and Custom HT1621 Driver

I built another clock. Not because I don’t already have clocks—I have plenty, including a few homemade ones. But if you start some big, complicated project, there’s a good chance you won’t finish it… even if you’ve got the long New Year holidays ahead.
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TP4054 - Current-Limiting Resistor Values

In my DIY projects, I frequently utilize lithium batteries and TP4054 chips to charge them. Charging current for a battery should not exceed 1 °C (capacity multiplied by one hour). At this rate, the battery will charge to full capacity in precisely one hour.
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CH340G programmer for ESP8266/ESP32 - updated version

CH340G programmer for ESP8266/ESP32 - updated version

So, I have returned to my last year’s design of the CH340G based programmer and upgraded it with the same pinout as the widely known ESP01 module for the better compatibility and the USB Type C receptacle. Nowadays connectors of this type are way more popular than outdated Micro USB ones.

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Using MPR121 touch keyboard controller with Arduino

Using MPR121 touch keyboard controller with Arduino

I added a tiny capacitive touch keyboard to the URU Card using the MPR121 chip—and it works great! The PCB has 12 touch pads, the setup is dead simple with I2C and the Adafruit library, and best of all… no debouncing needed. Smooth and responsive UI, just like I hoped.

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Universal ESP8266/ESP32 programmer

Universal ESP8266/ESP32 programmer

I finally built myself a universal programmer for ESP8266 and ESP32 boards using a CP2102 chip and a bunch of connectors. It’s simple, cheap, and works with everything—from ESP-01 to my custom URU Card. Full schematic, photos, and files are in the repo if you want to build one too.

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How to solder SMD components with stencil

How to solder SMD components with stencil

I finally tried using a stencil for soldering SMD components—and wow, total game changer. Ordered my URU Card PCBs + stencil from PCBWay, applied solder paste, placed the parts, hit it with hot air… and boom, working device in under 30 minutes. Bonus: I filmed the whole process in a quick tutorial!

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FPC1020 Fingerprint Scanner - detecting finger presence

FPC1020 Fingerprint Scanner - detecting finger presence

Back to FPC1020 driver work! I fired up an ESP8266 with Arduino to detect finger presence using the scanner’s built-in sensor matrix. It’s simple, fast, and could help optimize image capture—or even act like a button or gesture detector. Full example code and visuals inside!

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How to measure battery level with ESP32 microcontroller

How to measure battery level with ESP32 microcontroller

Figured out how to measure battery level on the URU Key using a simple voltage divider and some clever GPIO control. Threw in some ESP32 ADC math to convert readings into a nice 0–100% percentage—and even blink a red LED if the battery’s running low. BLE support coming too!

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Using ATECC508A Cryptographic co-processor with ESP32

Using ATECC508A Cryptographic co-processor with ESP32

Time to tackle the ATECC508A crypto chip! I started building an ESP32 component library to use it in my FIDO2 Authenticator. One chip gave me trouble, but another worked perfectly. Lots of I2C fun, ECC signatures, and some helpful inspiration from SparkFun’s Arduino library. One step closer to full hardware-based security.

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FPC1020A* Fingerprint Scanners

FPC1020A* Fingerprint Scanners

Finally got my hands on the FPC1020 fingerprint scanners! These things are tiny, SPI-based, and perfect for a built-in solution. I built test boards, hooked them up to a NodeMCU, and wrote a basic Arduino sketch to read the hardware ID. Next step: integrating with the main authenticator project!

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CH340G programmer for ESP8266/ESP32

CH340G programmer for ESP8266/ESP32

Slightly tired of big and long-running projects both at work and at home I decided to make a small spin-off project to help me working with ESP8266/ESP32 devices. Is there any reason to make it when there are a lot of cheap USB-Serial converters in the market? I don’t think so. My only reason to make it is to have cool addition allowing ESP8266s to be programmed automatically without flash/reset buttons but simple circuit with two transistors. Most of the USB to Serial converters simply do not have this circuitry on board. And, of course, I wanted to have some fun.

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