ITOHI — Open-Source Hardware, Embedded Systems & DIY Builds

Pavo20 Pro II GPS Fix Attempts: BEC Switching Noise at 1575 MHz and What Actually Helped

Thu, 09 Jul 2026 00:00:00 +0000

The Pavo20 Pro II is a capable 2.5" whoop — compact, powerful, with a good camera and a surprisingly solid video link even on linear whip antennas. I wanted it as a mountain trip quad: something that fits in a jacket pocket, dives canyons, and has GPS Rescue as a genuine safety net. GPS is not included; I added a module myself, soldered and configured it. That's when the problems started.

FPV Tuning with Sintra AI — And Why I'm Not Building Another AI Platform

Thu, 25 Jun 2026 00:00:00 +0000

This post grew out of the drone detector article, where I mentioned using Sintra for the FPV side of the work. That mention deserves its own treatment, because it raises a question I want to address directly: why am I using an external AI tool for this instead of building my own?

Why Sintra, Not My Own AI

There are projects in my history I don't talk about much. MentalMentor. BabyAI. Others at various levels of completion, none of which became products. The pattern is consistent across all of them: I build the technically interesting part — the architecture works, the core functionality is there — and then the work shifts to distribution, community building, marketing. Things that require either a budget I don't have or social capital I've never managed to accumulate. I have no network. I cannot self-promote. The projects expire quietly.

Training a Neural Network to Detect Shaheds and Quads from Audio

Mon, 15 Jun 2026 00:00:00 +0000

Live demo: drone-detector.sintra.site

A note before the technical content: the staggered training protocol described in this article was developed with significant help from Sintra AI. What started as a series of questions about why the naive P1→P2 schedule kept plateauing turned into a structured debugging conversation that identified the calibrated checkpointing problem and shaped the cycle logic.

FPV: how it all began

Mon, 01 Jun 2026 00:00:00 +0000

For years my drones travelled with me. A DJI Air first, then a Mini 3 — camera platforms that rode along on every trip, packed next to the rest of the gear. They were good at exactly one thing: hovering somewhere legal and taking a clean photo.

That was the problem. Hovering at the permitted altitude, framing a mountain from a respectful distance, felt underwhelming every single time. The footage was fine. It was also lifeless — the drone observed from a polite distance and brought back postcards. Eventually I stopped packing one at all. On motorcycle trips especially, the Mini 3 stayed home; the weight and the faff weren't worth another set of hover shots.

Building a Portable Visible Light Spectrometer with Raspberry Pi and Fiber Optics

Sat, 21 Feb 2026 19:48:00 +0200

After successfully reverse engineering the CR30 colorimeter, I found myself wanting something more versatile - a device that could not only measure reflected light but also handle transmittance measurements with fiber optic coupling. The result is this compact, portable visible light spectrometer built around a Raspberry Pi Zero 2 W and some clever optical engineering.

Why Build a DIY Visible Light Spectrometer?

While the CR30 colorimeter works great for surface measurements, it has limitations. I wanted a device that could:

Adventures in Color Science: Building a DIY Calorimetric Laser Power Meter

Sat, 21 Feb 2026 14:00:00 +0200

So here I am, a physicist who got bitten by the color science bug. What started as innocent curiosity about how light works has turned into a full-blown obsession with spectrometers, colorimeters, and now... laser power meters. You know how it goes - you start with one simple question and before you know it, you're knee-deep in soot-covered copper plates and differential amplifiers at 3 AM.

The thing is, I'm building up to something bigger: a Raman spectrometer. And for that, I need a proper 785nm IR laser diode. But here's the catch — I'm coupling light through cheap TOSLINK optical fibers (yes, really), and I needed to know exactly how much laser power I'm losing along the way. Spoiler alert: it's a lot. That's why my cuvette holder has the laser embedded directly in it.

Reviving a Dead Synology DS420+: A BIOS Recovery Adventure

Tue, 28 Oct 2025 15:30:00 +0200

One day my DS420+ just died. Well, not completely dead - it powered on, fans spun up, disks spun up too, blue LED blinked... but that was it. No network, no beeps, nothing. Just an expensive paperweight with my data trapped inside.

Initial Diagnostics

First thing I tried was removing all the drives. Sometimes a bad drive can prevent boot. Nope - same blinking blue LED.

DIY Color Calibration Chart: From Sublimation Printer to Acrylic Paint

Sun, 26 Oct 2025 18:00:00 +0200

The plan from the CR30 teardown: print a set of known color patches, measure each with the CR30, and use ArgyllCMS to build a correction profile. Simple in theory. In practice it took two completely different approaches before I got anything usable.

What ArgyllCMS expects

ArgyllCMS can generate a target chart — a grid of color patches with known Lab values — and then, after you measure each patch with a colorimeter, compute the delta between what you printed and what you intended. From that it builds an ICC profile or a Darktable color checker correction.

Adventures in Color Science: Reverse Engineering a Chinese Colorimeter CR30

Sun, 19 Oct 2025 20:05:19 +0200

I've always been fascinated by the intersection of hardware and software, especially when it comes to understanding how devices communicate. Recently, I developed a need for monitor calibration as well as properly color correct my photos. I've been looking at X-Rite, Datacolor and other calibration devices and am on the path of acquiring one of those. However, in the meantime I got this idea of creating a simple color chart that could substitute one of those ColorChecker24 cards for simple color correction. For that I needed to print an accurate replica of one of those charts so that Darktable and/or Davinci Resolve would recognize it. Of course it is impossible to do due to various reasons, but it is possible to produce one close enough for regular use(not scientifically accurate at all). For that purpose I have an old sublimation printer that only has CMY colors. Clearly not enough to produce the full gamut, but close enough. Or so I thought...

Exploring the sound of DML

Wed, 10 May 2023 20:01:28 +0200

My obsession with audio reproduction started with my first i386 PC. Back then, getting any sound out of a computer required creativity. I experimented with the internal PC speaker, directly accessing the timer IC to generate crude audio through clever PWM modulation. The results were terrible, but fascinating. Next came a DAC cobbled together on the LPT port - better, but still harsh. Eventually I graduated to mediocre Sound Blaster cards, though my very first experience with proper PC audio was actually through a Spectrum PC that featured a dedicated sound synthesizer chip. Programming that chip during the pre-internet era was an exercise in trial and error with photocopied datasheets.

Adventures with Hugo

Mon, 05 Dec 2022 20:05:19 +0200

I've been involved in Full Stack for a while now in one form or another(either maintaining, designing or working on Full Stack projects). Even during school time, I was building websites for myself and my friends. I've built sites commercially even. Although I've been using either pure HTML+JS or even PHP/Perl at some point. I rarely liked this activity, especially since the visual designs of the web pages were lacking and I just couldn't make myself study some visual design :(

ESP32 as Bluetooth audio receiver (A2DP sink)

Thu, 01 Dec 2022 20:01:28 +0200

I was building a Christmas set of spherical speakers just to familiarize myself with ADAU1401 Sigma DSP. And I wanted to add Bluetooth capability to the speakers so that they could receive sound data from an old Samsung Galaxy Note 10.1 in the kitchen.

Granted, I have ordered some Bluetooth audio receivers, however, while they are being shipped, I thought to myself: Hey, I already have powerful CPUs(ESP32) with Bluetooth. These chips have I2S and I have I2S DACs waiting for another project! Why don't I give it a try and just google some Arduino projects that connect ESP32 A2DP sink with I2S and use that as a receiver?

How Its Been in 2020-2022

Sun, 13 Nov 2022 12:46:27 +0200

Years 2020, 2021 and 2022 have been tough for almost everyone. The pandemic, the war, global economic collapse, bancruptcies in Crypto sphere... You name it. Although, for me it was a rather productive period(despite a divorce spanning almost 3 years), since I have accustomed to working from home and working on various project remotely. The range of projects varied from working on a system that tailors advertisements to people behavior to optimizing Internet traffic by cleverly and autonomously arranging relay nodes all around the globe. All these projects mainly keep the food on my table and fund my other, more experimental, theoretical or sometimes even absurd ideas.

Multilanguage Test

Fri, 13 May 2022 18:26:47 +0200

This is a simple test for multilanguage support. Sometimes I feel like writing in native tongue, sometimes in multiple languages... So, let's see how that goes.

Here's a comic strip about why I have so many unfinished projects:

Esp8266 Driven Oven Controller Over Web Ui

Sat, 13 Jul 2019 17:44:47 +0200

!!! WARNING: This project deals with mains power and high current !!! Please be careful if you wish to replicate any of its functionality and never work on a PCB or any open wires that are connected to the mains ! Author has no responsibility for your safety and wellbeing, so please take care of yourself.

How it works

The purpose of this project is to control a heater of any sort to facilitate SMT reflow soldering utilizing a predefined temperature profile. Control of the heater is performed by ESP8266 or ESP32 chip via Web UI over WiFi.

Arduino ESP8266 Smart Motion Sensor using PIR and MQTT

Fri, 19 Apr 2019 01:01:28 +0200

My son has a cat. And I've become very curious about the cat's feeding and toilet habits. Mainly I'm interested in how long does it take him to go to the toilet after eating as I've noticed a pattern: At first he goes to the kitchen, eats and then runs around the house wrecking havoc for some time and then goes to the toilet. So I'm curious whether this is his usual routine and moreover how many times during the day and night does he need to use his toilet. I might even build a collar for him to track the magnitude of his movements in the future :)

Building ESP8266 Weather station with BME280 (part 2)

Mon, 15 Apr 2019 01:01:28 +0200

In a previous post I've described how to build a Weather Station based on ESP8266 chip and various breakout boards you can buy e.g. on Aliexpress. In this post, however I'll share with you how I built a standalone PCB boards containing all the required components. To recap - this is a ESP8266 based Weather Station, that measures surrounding air temperature, humidity, pressure along with light and battery voltage. Connects to an MQTT broker and reports it's data there. There are three variants: bare board with no display, which can be connected to a lipo battery, solar panel and sit somewhere with plenty of sunlight for ages, or it can have either an ePaper display or 0.96" OLED display and sit on your desk.

Arduino Metal Detector using frequency counter and OLED display

Sun, 08 Jul 2018 01:01:28 +0200

There are a lot of forests in Lithuania which I like exploring on my bike. In the past a lot of Lithuanian resistance troops resided in those forests, so there is a big probability to stumble upon a stash of some kind. However that stash might as well be a grenade or a bomb of some kind, but nevertheless I always wanted to combine my motorcycle riding through the woods with treasure hunting and some time ago I decided to build a simple metal detector. Granted there are lots of metal detector designs, like BFO, VLFD, PI and so on (I'll briefly cover some of them in the theory section). Some of them I've tried in the past with various results and then during one boring evening of browsing the internet I stumbled upon this blog and decided to build this type of metal detector. The design is really simple - there is a simple oscillator circuit and a frequency counter. When the coil passes over or near various ferromagnetic or paramagnetic materials the frequency of the oscillator changes and based on this change you can decide where to dig. Moreover since the frequency counter can be implemented on any microcontroller you can analyse the frequency change in many different ways potentially enabling metal differentiation and even filter out frequency drift, that plagues other types of detectors.

Arduino Developing with Atom IDE and PlatformIO for AVR and ESP chips

Thu, 05 Jul 2018 01:01:28 +0200

There are many different ways to develop and deploy embedded solutions, one of the most popular ones would be Arduino IDE. But the editor is very simplistic, without handy features such as intellisense, code refactoring and many others. I've used AVR Studio, IAR, even VIM to develop code for AVR/STM microcontrollers.. But they are either designed specifically for that platform or are commercial products. And I love Open Source :)

Python development with Visual Studio Code

Thu, 05 Jul 2018 01:01:28 +0200

VS Code is an light but powerful editor developed by Microsoft. I have been using this editor for Python and embedded development(using PlatformIO) for a few months now.

Using PlatformIO with VSCode is rather simple - just install it through built in package manager and you're good to go. However python development needs a bit more work to setup properly. Especially if you want to develop Django apps with VSCode. That is what I'll be covering here in this post.

Building ESP8266 Weather station with BME280 (part 1)

Tue, 03 Jul 2018 01:01:28 +0200

Ever since I started playing around with ESP modules I wanted to measure weather conditions in multiple location at home, friends, etc. The best way to achieve that would be to build a station that gathers various environment parameters and publishes them somewhere. That is what I've done. The very first prototype was done using ESP-1 module, DHT-11 humidity sensor and BMP280 breakout board. The station publishes gathered data to a MQTT broker from where it can be further gathered and analysed.

Building ESP-1 balancing robot

Mon, 02 Jul 2018 01:01:28 +0200

I was always fascinated with balancing robots and wanted to build one myself. Some time ago I started collecting IMU, arduino boards, wheels, motors for other wheeled robots and one day decided to build a balancing robot instead. I've used wheels from old four wheel drive robot that used mouse sensors for odometry and was driven by an Arduino Pro mini. That robot never went alive anyway :)

Originally the robot was built using Arduino pro mini and all it could do was balance. I was thinking to add BT module to control it until I discovered that I have ESP8266 lying around. Also I decided to use a better IMU algorithm instead of DPU of the MPU6050. Thus the ESPBalancingRobot was born. It does use DC motors to balance and no encoders. Speed is being estimated using PWM signal averaging and constant angle is maintained using a double stage PID controller.

ESP8266 Wheelie

Mon, 02 Jul 2018 01:01:28 +0200

As I've mentioned in the last blog post, I was trying to build a four wheel drive robot using arduino that utilizes two A3080 mouse sensors for odometry. Sadly that project never got finished and I disassembled the robot and built a balancing robot instead. However later I decided to not abandon the four wheel drive robot and ordered several ADNS3080 sensors with proper optics, obtained an electric wheelie toy, which lead to the birth of this WiFi controlled toy car.