Ondrovo.com

Tangara docker dev setup

ondra@ondrovo.com (Ondřej Hruška) — Sun, 13 Apr 2025 23:49:09 +0200

I started editing the Tangara firmware - after all, it cost me a lot of money, so might as well try.

Esp-idf is notoriously a mess and I have had some problems with python versions an pip and whatnot in the past. This setup uses pre-built docker images to avoid that pain.

My Tangara firmware fork can be found here on gitea - branch “custom”: https://git.ondrovo.com/MightyPork/tangara-fw

To work with it, I recursively cloned the tangara project into a folder called tangara-fw. In the parent directory, I created a Makefile with these launchers:

Tangara first impressions

ondra@ondrovo.com (Ondřej Hruška) — Sat, 12 Apr 2025 22:02:21 +0200

Last year I joined crowdfunding on the Tangara music player. They had many delays and then problems with shipping and I only received it yesterday. This article will try to sum up my impressions and opinions so far.

Packaging

Very nice, professional looking box, a small printed user guide. Very nice. I noticed there is a guide only when putting the packaging away but hey, it is there and has all the regulatory stuff on it.

NanoVNA as a RLC meter

ondra@ondrovo.com (Ondřej Hruška) — Sun, 05 Nov 2023 09:24:07 +0100

Building anything RF-related, like filters or amplifiers for ham radio, you quickly find you need a way to measure capacitors and inductors, especially homemade ones like air-wound coils. You can use online calculators to get the number of windings, but there are just too many variables that affect the result.

You will also find the value varies with the operating frequency, this is normal and fine if the change is not too fast. I never really thought of this and kind of ignored things like parasitic capacitance, but you can’t get away with that at RF.

Výprava k nejzápadnějšímu bodu

ondra@ondrovo.com (Ondřej Hruška) — Tue, 19 Sep 2023 22:32:38 +0200

Praha — Panenský Týnec — jezero Most — Boží Dar — Kraslice — Aš — Františkovy Lázně — Krásno — Rakovník

Středa až neděle 6.—10. 9. 2023

Tohle je deník mého zatím nejdelšího vícedenního cyklovýletu. Něco v tomhle smyslu jsem plánoval delší dobu, na jaře 2023 jsem se konečně rozhoupal a zakoupil gravel kolo a brašny. Mým dlouhodobým cílem je na kole dojet k moři, to je něco přes 600 km a vychází to zhruba na týden cesty (a pak nějak zpět, vlakem nebo busem; 1200 km už je trochu moc). Tady jsem chtěl otestovat vybavení a hlavně jestli to dokážu reálně ujet.

Design for 3D printing in FreeCAD, part 1

ondra@ondrovo.com (Ondřej Hruška) — Sat, 18 Feb 2023 00:00:00 +0000

Welcome to my short tutorial on how to use FreeCAD to draw models for 3D printing. I will try to summarize the basics and the techniques I use, so hopefully you can spend less time cursing FreeCAD and more actually drawing and printing.

FreeCAD is a pain to get into as a beginner, the learning curve is steep and the software is buggy and acts weird when not used just right. I have a theory why this is so - all the developers spent so much time using FreeCAD, thet no longer hit the bugs, so nobody spends time fixing them. Some things get fixed over time, of course - your mileage will vary.

Weather station

ondra@ondrovo.com (Ondřej Hruška) — Sat, 04 Feb 2023 15:59:18 +0100

Here’s another project I had on the TODO list since forever, suddenly becoming possible and easy with a 3D printer. It has some history - I initially just wanted to measure and log outdoor temperature, so I had a water-proof DS18B20 probe on the balcony. It worked fine, but in sunny weather, the balcony and the wall heated up like an oven and the sensor reported temperatures over 50°C. The proper way to do this is to have the sensor mounted in a white-painted wooden box with slated walls called a Stevenson screen. It also shouldn’t be on a balcony… well, it is what it is :D

Fixing Arduino bootloaders

ondra@ondrovo.com (Ondřej Hruška) — Fri, 16 Dec 2022 19:35:56 +0100

Refreshing my stock of Arduino Nano and Pro Mini clones from AliExpress, I got some with weird or broken bootloaders. This article details how that can be fixed. I think I’m mostly writing this for myself in the future.

Flashing AVRs

Bootloaders in AVR

Bootloader is a second, smaller firmware (beside the application firmware), which allows the microcontroller to program its own flash memory. This may sound mysterious, but there’s nothing so special about it.

Reverse TÄRNABY

ondra@ondrovo.com (Ondřej Hruška) — Sun, 04 Dec 2022 22:48:30 +0100

The IKEA lamp “TÄRNABY” with the vintage style bulb is really nice when you want to build cozy atmosphere. The design is based on classic kerosene lamps and there’s even a dimmer knob simulating wick length adjustment—just without the stench and soot.

Well, this article isn’t meant to just praise the lamp, it’s about how I modded it to better suit my needs. The dimmer knob is on the side of the lamp. Depending on your particular arrangement, that may be just what you want, or it may be really awkward, the thick power cord wrapped around the lamp, knob hard to reach, etc.

Mochi

ondra@ondrovo.com (Ondřej Hruška) — Thu, 20 Oct 2022 23:44:40 +0200

Pics of my experiment to make Mochi from a recipe I found somewhere online (and didn’t save).

The filling was a paste made from Anko beans. They were pretty good.

Ocarinas

ondra@ondrovo.com (Ondřej Hruška) — Thu, 20 Oct 2022 23:38:09 +0200

Some of my first printing experiments.

The models are from Printables with some custom modifications.

Fun fact: If you scale an ocarina, it changes the pitch. Not that the original sounded particularly good.

Prusa Mini+

ondra@ondrovo.com (Ondřej Hruška) — Thu, 20 Oct 2022 23:36:04 +0200

I bought a Prusa Mini+. This is a gallery from building it and my first test prints.

I later replaced the 0.4mm nozzle for 0.8mm for faster structural prints and better results with transparenct material. I also bought the filament sensor addon.

The printer is reliable for occassional use and if you are tight on space and money, it’s a good deal. I still have it in 2026 and it works fine.

Project Trays

ondra@ondrovo.com (Ondřej Hruška) — Thu, 20 Oct 2022 23:12:00 +0200

This was a project to make these nice plastic trays stackable. It somewhat worked.

In 2026 I no longer use them and don’t know where the feet went. I still have the trays.

The model is uploaded to Printables.com

Geiger Experiments

ondra@ondrovo.com (Ondřej Hruška) — Thu, 20 Oct 2022 23:05:03 +0200

I bought some geiger tubes from eBay and got them working with an esp32.

The circuit is very simply:

a boost converter with the switchign driven by PWM
a super-fast diode and a high voltage capacitor
voltage for feedback measured with some many-megaohm voltage divider
tube pulses amplified by a darlington pair

I later turned this into a permanent installation for radiation monitoring, and a portable geiger counter (click through the article tags)

Ivar Kitchen

ondra@ondrovo.com (Ondřej Hruška) — Thu, 20 Oct 2022 23:04:11 +0200

I didn’t have any money at that time so I just furnished the kitchen from what I had. Over time it got more fleshed out.

fridge
sink
top shelf
oven shelf
fume extractor

I later replaced the ceramic cooktop with Sencor induction 2-hob. It looks kinda ghetto but everything is on hand and it is actually very practical.

PCB Etching

ondra@ondrovo.com (Ondřej Hruška) — Thu, 20 Oct 2022 23:03:12 +0200

While I learned to design and solder PCBs much earlier, until this year I never tried to make my own.

There are many ways to do it, for example:

dry method with a CNC milling machine - if you have the machine, this would be a very appealing method. No chemicals, relatively quick and well reproducible.
etching with etching salts - probably the cleanest chemical method, but you have to buy the salts
etching with ferric chloride - the classic, this is a messy method and makes brown stains
etching with cupric chloride - similar to ferric chloride, this solution is self-regenerating and can last basically forever, plus it doesn’t stain

Electrolysis experiment

First, I tried to use good old electrolysis just to see if it could work. It does, kinda. The problem is that electrolysis is never perfectly uniform and tends to create islands of unetched copper, which then can’t be etched further because of the broken connection. This clearly doesn’t work for large uncovered areas. I believe you could design your boards specifically for electrolysis, with minimal exposed areas, and when done, fix it up with a Dremel or a cutting knife. This might be worth exploring if you can’t get the chemicals needed for other etching methods.

Air Quality Sensor

ondra@ondrovo.com (Ondřej Hruška) — Thu, 20 Oct 2022 23:02:13 +0200

This project connects several air quality sensors to ESP32 and exposes it as a REST API with JSON and also Modbus.

The firmware can be found at https://git.ondrovo.com/electro/esp-airsensor where you can also find more details in the README.

There is nothing particular about the design worth noting. It works longterm except for the CO2 sensor which is rather flaky. I can’t recommend this model. It’s powered by an old phone charger.

Dremel Drill Stand

ondra@ondrovo.com (Ondřej Hruška) — Tue, 18 Oct 2022 00:00:00 +0000

When you have a Dremel and want to drill some PCBs, what do you do? Buy a drill stand for the Dremel, readily available and not terribly expensive?

No: Make a DIY drill stand from a macro slide you bought on AliExpress and waited for it 3 weeks.

Bad macro slide from Aliexpress

That sounds logical, right? Indeed, so, here’s how that went:

Fitting a Dremel to the slide

Handle modelled in OpenSCAD

Testing if it could work

Final build using a particle board

It works pretty well, actually. It just takes a bit too much space.

Pokojový rekuperátor

ondra@ondrovo.com (Ondřej Hruška) — Mon, 19 Sep 2022 00:00:00 +0000

Zakoupil jsem pokojový rekuperátor Zephir LUX. Nakonec jsem elektroniku skoro celou vyhodil a nahradil, takže by stačil levnější model, např. Zephyr Z50, ale o tom později. Nemám bohužel srovnání, zda tento způsob větrání je skutečně úspornější než otvírat okno, ale i samotná možnost vyvětrat na dálku nebo automaticky, když je zrovna venku teplo nebo uvnitř špatný vzduch, má něco do sebe. Určitě by to šlo udělat hezčí a míň “hobby”, ale, no, funguje to.

Homebrew SSR

ondra@ondrovo.com (Ondřej Hruška) — Thu, 08 Sep 2022 00:00:00 +0000

I thought Solid State Relays (SSRs) are way overpriced and could be made cheaper from scratch. So, I took one apart and traced the circuit…

Disassembled commercial SSR

Front and back side overlaid

The hand-drawn schematic has the triac upside down, it doesn’t work that way. Here’s a corrected version:

The final, verified schematic

Don’t use a 150R resistor in place of the 100R + 47R. It’s like that on purpose, the resistors have a breakdown voltage that must not be exceeded. You can even split it to more resistors to be extra safe. I wouldn’t recommend using small SMD ones. The original SSR used MELF resistors, regular through-hole ones are fine too.

libinput scroll fix for MX Master 3

ondra@ondrovo.com (Ondřej Hruška) — Thu, 23 Jun 2022 19:20:46 +0200

libinput 1.19 changed scrolling behavior such that it broke my mouse, MX Master 3, and other models that have a built-in support for high resolution scrolling. It seems each vendor did hi-res scrolling differently, so it might work right for some other mice.

The way this bug manifests varies, here are some examples:

very slow scrolling in a browser
too fast tab switching by wheel
Okular in continuous mode lost the ability to flip through pages by the wheel. I thought it’s actually an Okular bug, but it disappeared after applying this work-around.

I don’t think there was any need to fix scroling, it worked fine, same as I don’t think Inkscape needed a UI rewrite that made it lose features, and Gimp didn’t need new grayscale icons that are harder to use (luckily can be turned off).

Remostat

ondra@ondrovo.com (Ondřej Hruška) — Tue, 07 Jun 2022 00:00:00 +0000

Remostat je regulátor výkonu remosky. Remoska, v žádné verzi, nemá nastavitelný výkon, jediná regulace spočívá v PTC efektu topného tělesa. Většinou to stačí, ale když peču chleba a hodně vyběhne, vršek má tendenci se připalovat. Díky remostatu můžu po prvních cca 20 minutách výkon ubrat na 3/4 až 1/2 a nechat chleba pozvolna dopéct. Regulace výkonu se uplatní i při jiných receptech, např. u zapečené zeleniny, francouzských brambor atd.

Díky tomu, že remoska používá odporové topné těleso s poměrně pomalou odezvou, úplně postačí pomalá regulace pomocí PWM. Střída je efektně znázorněna blikající LED i přímo doutnavkou na vypínači. Klasický triakový regulátor, jaký se používal k vrtačce, by pochopitelně také fungoval.

Magloop Antennas

ondra@ondrovo.com (Ondřej Hruška) — Wed, 18 May 2022 01:33:39 +0100

Magnetic loop is, in my experience, the best receiving antenna for the lower bands (40m and below).

A pre-amp also helps but is not strictly necessary.

The simplest design is just a loop of specially connected coax, fancier ones also add a Balun.

There are also designs for a more rigid transmit version, but I am not interested in that at the moment.

Simply search “magnetic loop”, there are many guides to build these.

Receiving SSTV

ondra@ondrovo.com (Ondřej Hruška) — Fri, 15 Apr 2022 02:03:01 +0100

SSTV is a popular way to transmit images over HAM radio. One frame takes tens of seconds so it’s more like postcards than TV.

You can receive with SDR and any suitable antenna. There are well known frequencies the HAM community uses for this sort of activity.

Sadly my place has a lot of QRM right in the SSTV band, so reception is spotty.

SDR Interesting Signals

ondra@ondrovo.com (Ondřej Hruška) — Mon, 11 Apr 2022 01:29:41 +0100

After buying my first SDR dongle I spent too much time browsing through the RF spectrum, so this is a collection of the more interesting signals I saw. Some can be identified using SigID wiki, some are a mystery.

You can also play some bonus audio clips.

QRM Eliminator

ondra@ondrovo.com (Ondřej Hruška) — Wed, 06 Apr 2022 01:55:44 +0100

I built this using a schematic of a X-Phase QRM eliminator I found online. It was a bit involved but with a custom made PCB not so difficult to build.

The basic principle is that you capture noise on a low quality antenna (diversity antenna) and blend it with the signal from your good antenna, with the opposite phase. The circuit lets you tweak the phase shift and magnitude using the three knobs. Using this device is a lot about finding the right settings for the exact frequency you want to receive, and fiddling with the diversity antenna.

Miniwhip

ondra@ondrovo.com (Ondřej Hruška) — Fri, 18 Mar 2022 01:38:36 +0100

Specifically, I tried to build a PP-Whip, which is a derived design.

Miniwhip is used in many WebSDRs.

It didn’t work. Or rather, I had no suitable place to test it on and it didn’t work on the balcony. You are meant to place it in the middle of a grassy yard or on a flat roof.

Fun to build though.

Receiving NOAA with QFH

ondra@ondrovo.com (Ondřej Hruška) — Sun, 06 Mar 2022 01:47:43 +0100

This is a photo blog of my experiments with receiving the NOAA satellites. These broadcast the meteo image to the ground as they fly around the planet, it’s kinda silly, like a giant scanner that captures the whole continent and sends it back row by row. There is no encryption and no integrity codes, you just tune your receiver to AM, use the right software, frequency tracker and hope for the best.

AM-blocking antenna filter

ondra@ondrovo.com (Ondřej Hruška) — Wed, 02 Mar 2022 00:00:00 +0000

This multi-element filter was designed to block AM broadcast so I have better access to the LF and VLF bands.

It somewhat worked, but I expected more from the calculation. The SMD inductors I used might have been inappropriate for the design, but I tried air-core wirewound ones too and that was not much better.

RF Noise Generator

ondra@ondrovo.com (Ondřej Hruška) — Tue, 01 Mar 2022 01:43:19 +0100

I hope to find the schematic and add it here later. I think the noise is created on a reverse biaded diode.

You can use this to measure RF filters without a VNA, just measure the signal using a SDR.

In-line Powered Antenna Preamp

ondra@ondrovo.com (Ondřej Hruška) — Wed, 23 Feb 2022 00:00:00 +0000

The idea is that the power is sent through the coax to the preamp that sits right at the receiving antenna, and the RF from the preamp is modulated on top of the DC and goes through a foil capacitor to the receiver.

I’m writing this page 4 years late (2026) so I forgot the design used. I may update this with more info in the future. Just gotta say it worked spectacularly for a magnetic loop antenna.

SDR Nooelec

ondra@ondrovo.com (Ondřej Hruška) — Tue, 15 Feb 2022 01:45:47 +0100

This article documents the saga of trying to fight interference and flaky USB port on the NOOELEC stick. It is otherwise a capable SDR but has some flaws, namely overheats to hell, has a lot of interference, and has a wobbly port. For first experiments with the RF spectrum it was well adequate though.

This project ended with me getting a good stick instead (the RTL-SDR Blog one)

ADS-B

ondra@ondrovo.com (Ondřej Hruška) — Tue, 18 Jan 2022 01:13:39 +0100

Experiments with receiving ADS-B (Flightradar signals)

The best antenna type proved to be “1/4-wave ground plane”, which is the one wire with 4 or more beans pointing downwards, but you can receive this on almost anything if it has the right length. The fish can was funny but not very good as an antenna.

For best results, find an on-line calculator and get the dimensions exactly right.

Also note that it is very important to have line of sight view of the planes, I could only see one side of the sky due to receiving on a balcony.

Crate Solder Station

ondra@ondrovo.com (Ondřej Hruška) — Sat, 18 Dec 2021 00:00:00 +0000

Soldering and rework needs many specialized tools and accessories good for nothing else. If you don’t have a workbench where all this stuff can be left lying around, it becomes a problem. I solved this by mounting everything in an IKEA crate, including a small lamp and a fume extracting fan. The whole thing can be moved around, always ready yet not taking up much space.

No point in writing about this, have some pictures:

Easy Pho Recipe

ondra@ondrovo.com (Ondřej Hruška) — Wed, 09 Oct 2019 00:00:00 +0000

I’ve been trying to replicate the delicious pho soup you can get in pretty much any Vietnamese restaurant or fast-food. It has this very specific taste–not overpowering, a sort of pleasant blend of different spices. It comes in many variants, and I think every Vietnamese family will have their own version. You can have chicken pho (Pho Ga) or beef pho (Pho Bo). I made the chicken version, in part because chicken is cheaper, and because I happened to have some chicken breasts in the fridge.

Blocking rap on Spotify

ondra@ondrovo.com (Ondřej Hruška) — Sat, 02 Mar 2019 00:00:00 +0000

I never liked rap or hip-hop, but I keep getting it in my radios and automatic playlists on Spotify. There’s no way to blacklist a genre in Spotify. But there’s a way to do it with an “add-on”.

Introducing: Bread Gallery

ondra@ondrovo.com (Ondřej Hruška) — Sun, 03 Feb 2019 00:00:00 +0000

If you follow my microblog rambling, you know I spent several evenings and a weekend with a brand new silly side project: Bread Gallery

The gallery can be found here: www.ondrovo.com/bread

It’s fully static, generated by a Rust script. Just because. There’s no good reason to do this in Rust; but yeah, it’s really fast because of it–and I didn’t even multi-thread it yet.

About bread

I started baking my own bread just after moving out, as you can see when you look at the oldest bread’s date - September 2018. Since then I maintain a sourdough starter culture and very rarely buy bread from the store.

Kitchen renovation: New cooker and a stand for it

ondra@ondrovo.com (Ondřej Hruška) — Sat, 19 Jan 2019 00:00:00 +0000

I finally got fed up with the old cooker that was in the kitchen (see pic) and bought a more modern one. However, there was a small problem: the old cooker was embedded into a kind of metal box that served as a storage space. Very poorly designed one, because you couldn’t quite reach to the back, and a lot of space was wasted under it as well. But importantly, it filled the hole next to the kitchen cupboards and a wall. That was gone now. What do??

Bird feeder

ondra@ondrovo.com (Ondřej Hruška) — Mon, 10 Dec 2018 00:00:00 +0000

This is really going be just a photo dump, because there’s not much to say about a bird feeder. I spent about a month on this.

Feeder base and roof

Mess on my dining table

Finished feeder

The hardest bit was figuring out a way to attach it to the balcony. The rope you can see in one of the photos was just to make sure it doesn’t fall down when I tried to install it. It’s actually quite stable, if not exactly horizontal. You can’t see that from the room tho, so it doesn’t matter. And birds don’t care.

Making quince cheese

ondra@ondrovo.com (Ondřej Hruška) — Sat, 20 Oct 2018 00:00:00 +0000

I got a bunch of small, “decorative” quinces from the community garden. It’s from Chaenomeles Japonica, Japanese Quince tree. Or rather a bush. They smell really nice, but you can’t eat them, they’re super sour. Just awful. Perhaps this is why hardly anyone tried to cook them. Mistake! They’re perfectly good when cooked. Okay, still a bit on the sour side, but not too bad.

Japanese quice fruits ready for picking

For the actual recipe I’ll point you to your search engine of choice, because a) I don’t remember it exactly, and b) don’t want you to blame me for it coming out bad :P

Building a kitchenware rack

ondra@ondrovo.com (Ondřej Hruška) — Mon, 15 Oct 2018 00:00:00 +0000

I have a small kitchen, and space is at the premium. However, there was this nice empty wall next to it.

I bought some planks, gave them a good double layer of transparent varnish, and furnished them with screw-in hooks. Voilà…

It’s cheap, practical, and also looks nice.

Just figured someone might use the inspiration ^_^

Fruit & herbs drying racks

ondra@ondrovo.com (Ondřej Hruška) — Sun, 30 Sep 2018 00:00:00 +0000

After I got my IVAR shelves, I decided to add a set of fruit and herb drying racks to them. You can’t buy these in IKEA, I built them myself. It was really quite simple, so here’s just some pics.

First, the shelves; the apartment looks horrible, empty like this. I didn’t even have a bed when I did this, go figure. It’s much cozier now (writing this in Feb 2019, after I remembered I never blogged this, oops). Shelves, behold:

Painting IKEA chairs

ondra@ondrovo.com (Ondřej Hruška) — Thu, 20 Sep 2018 00:00:00 +0000

Here’s a project update from Sep 2018, when I moved to my own place and started furnishing it, largely from IKEA. I remembered to post this going through my photos backlog in Feb 2019, so the article is a bit back-dated. But anyway, here it comes

IVAR chairs. You may know IVAR from IVAR shelves, but it’s actually a whole line-up of cheap wooden furniture.

I got these chairs because I’m a cheapskate, but also they seemed quite OK.

Improving the NORDEN gateleg table

ondra@ondrovo.com (Ondřej Hruška) — Sun, 16 Sep 2018 00:00:00 +0000

NORDEN is a gateleg table (with foldable desk) from IKEA. I bought it without much thought because of the nice look and it seeming ideal for my small apartment. I quickly discovered some flaws in its design, but they could be fixed without much trouble.

This article lists the problems I had with the table, and my solutions to them. I’ll try to explain the modifications so that anyone could follow, but if you have any questions, please don’t hesitate to ask for details. I’m not sure about the English terminology in some parts, but you should figure it out from the photos.

Cucamelons: Seed to Harvest

ondra@ondrovo.com (Ondřej Hruška) — Sun, 15 Jul 2018 00:00:00 +0000

If you never heard of cucamelons, also known as mouse melons, or mexican sour gherkins, you’ll be in the same position I was earlier this year when I came across their seeds on eBay. Those vines are applauded in a number of gardening blogs, which you will easily find on Google, as a hardy and tasty addition to the garden. I wanted to try it.

First, I live in an apartment without any garden, so I started looking for community gardens in Prague. Before long I was a member of one such gardening club, quite far away but within a 40-minute bike ride or 30 minutes by the metro. Not too bad. This was March, still plenty of time before I could plant anything. But the seeds arrived, and I was impatient.

First prototype PCB for GEX

ondra@ondrovo.com (Ondřej Hruška) — Thu, 08 Mar 2018 00:00:00 +0000

This is just a quick update about the GEX project: the OSH Park PCBs finally arrived, and they work!

Some pics from the first board’s assembly and testing:

Circuit boards

MCU on board

USB

HUB circuit board

Rainbow gex

I made some mistakes in the layout, but they were easy to fix, and electrically everything seems to work just fine. No big deal, finding bugs in the schematic is why I made this board to begin with. If it doubles as a useful tool, that’s of course a plus.

STM32 Touch Sense

ondra@ondrovo.com (Ondřej Hruška) — Sun, 25 Feb 2018 00:00:00 +0000

GEX has been going steadily forward over the fast few months and is now roughly 80% feature complete; the only notable missing features are PWM output and DAC.

To take a break from the horrors of timer synchronization I went through last week, implementing frequency measurement, I took a look at the Touch Sensing Controller (TSC). There’s not much reason to have this implemented in GEX, as the project is mainly meant to be used as a data acquisition or an experiment automation kit. However, the used principle is interesting enough to warrant a closer look, and it will serve as a nice demonstration.

GEX experiment: RGB ambient lights

ondra@ondrovo.com (Ondřej Hruška) — Mon, 11 Dec 2017 00:00:00 +0000

Here’s a thing I wanted to do for a long time and the idea that actually made me think of creating GEX. The firmware is still in super-early alpha, not even published yet, but I got Pin and Neopixel units working and put together some hacky screengrabber script, so here we go!!

I wanted to have nice ambient lighting for watching movies that e.g. turns dark in dark scenes, blue underwater etc. This has been done a million times before, so, uh, i++.

SD card adapter hack: A sheet music light!

ondra@ondrovo.com (Ondřej Hruška) — Mon, 11 Dec 2017 00:00:00 +0000

Here’s a quick log about a hack I built a couple days ago: Exploiting a SD card slot to power a LED light for my piano’s sheet music tray!

There’s nothing complicated about this hack and you can easily build it too with a few parts from your drawer. The key observation is that SD cards are powered by 3.3 V and can draw up to 100 mA. My piano doesn’t have a host USB socket, so this is the only access to power on it.

Introducing: GEX

ondra@ondrovo.com (Ondřej Hruška) — Fri, 08 Dec 2017 00:00:00 +0000

I don’t update this site as often as I perhaps should, but if you follow me on Mastodon it would be hard to miss my yellings at various development tools and frameworks with ever increasing cadence.

Since early spring 2017 I’ve spent most of my free time working on ESPTerm, a WiFi terminal project I mentioned in the previous post here. It’s now complete as far as the original plans go, with many additional features added that I didn’t think of until later, and a few more still planned. Those additions to ESPTerm are based on suggestions from the slowly growing community, as well as my experience with actually trying to use it and finding what could be improved. The module is presently being tested by some students in an embedded electronics course, which will hopefully bring in more feedback and help push it further.

Don't buy this cheap FTDI adapter!

ondra@ondrovo.com (Ondřej Hruška) — Sat, 18 Mar 2017 00:00:00 +0000

Just a quick post to warn you about this terrible product.

If you’re shopping for a USB-serial adapter, you’ll come across those cheap red ones. Don’t buy them. I just spent 4 hours trying to debug my ESP8266 programmer I was trying to build, where I used one of those and it’d always freeze at 85%.

Don’t repeat my mistakes–yet again, going for the cheapest option “paid off”.

Here’s a blog post where someone was having the same issues, and indeed tracked it down to the bad adapter: esptool-ck, esp8266, and FTDI Bug Hunting. Sadly, I found it too late. He then proceeds to test a variety of different adapters: esptool USB Serial Adapter Shootout.

Wireless Terminal with ESP8266

ondra@ondrovo.com (Ondřej Hruška) — Thu, 16 Mar 2017 00:00:00 +0000

Here’s a ~~short~~ write-up on a thing I’ve been working on recently. It lets you add a wireless interface to any of your breadboard projects, conveniently implemented as a terminal emulator accessible over WiFi.

Updated Jan 2018: see the bottom!

First, how this came about: It’s a small university project, a device for students to add some “IoT oomph” to their seminar breadboard builds. It’s aimed to be easy to use, hard to damage, and above all, fun to mess with for to the aspiring embedded hackers.

Determining the ESP8266 power consumption

ondra@ondrovo.com (Ondřej Hruška) — Tue, 07 Feb 2017 00:00:00 +0000

Intrigued by the schocking revelations from the previous article, I took the ESP8266 to the lab and measured it with a proper oscilloscope.

Here I present my measurements, as well as some screenshots of the waveforms. The measurements were performed on an ESP-01 module using LeCroy WaveRunner 6050A and it’s accessory current probe, as pictured (the probe os off-screen):

ESP8266 killing itself?

ondra@ondrovo.com (Ondřej Hruška) — Sun, 05 Feb 2017 00:00:00 +0000

ESP8266, a popular WiFi chip with many undocumented “features”. Here’s one nasty one, which can cost you the WiFi module.

I’ve observed this issue on ESP-01 and ESP-12 modules, and heard it also occurs on ESP-03. I believe it’s safe to assume it can happen to any module.

Introduction

The ESP is a power hungry chip, normally using about 70~~mA with frequent short current spikes (1~~us at about 400~mA). Those can, to a certain extent, be suppressed by small ceramic capacitors. You’ll still be getting some Vdd ripple, but that could be fixed with a choke (optional) followed by a larger capacitor. Basic stuff.

Getting started with STM8 on Linux

ondra@ondrovo.com (Ondřej Hruška) — Sat, 07 Jan 2017 00:00:00 +0000

In the previous article, we had a look at the cheap STM8 board from eBay and the ST-Link dongle you need to program it. Now it’s time for some action!

Setting up the environment

Literature & examples

It’s always a good idea to start with some reading.

There’s a wealth of free materials provided by ST about our chip (STM8S103F3). The page also lists all the main features of the microcontroller, if you want to have a look.

A first look at the STM8

ondra@ondrovo.com (Ondřej Hruška) — Thu, 05 Jan 2017 00:00:00 +0000

If you, like me, are in the habit of browsing eBay for cheap electronic bits and pieces, you may have stumbled upon this ridicuously cheap STM8 board (eBay, AliExpress). How does it compare with Arduino?

In this post, I’ll present my initial findings about the mysterious microcontroller and the board it comes on. If you’re so inclined, the chips can be purchased separately as well.

How to reduce systemd stop timeouts

ondra@ondrovo.com (Ondřej Hruška) — Sun, 18 Sep 2016 00:00:00 +0000

If you’re running a systemd-based Linux distribution, such as Arch, you might have came across this weird glitch - a 90-second countdown when you try to turn off the machine.

Ctrl-C, Ctrl-D don’t work, you either wait, invoke REISUO, or hold the power switch. If you’re sick of this ritual, this article may have a solution for you.

Open the /etc/systemd/system.conf file with your favourite editor (you need sudo), and look for a (commented out) line with DefaultTimeoutStopSec.

Fixing TTY resolution with proprietary NVIDIA drivers

ondra@ondrovo.com (Ondřej Hruška) — Sat, 17 Sep 2016 00:00:00 +0000

You had enough of nouveau, installed the proprietary NVIDIA driver, and now your TTYs have giant blurred font and look like trash. I’ve struggled with this issue a lot in the past, but now I finally have a fix, and it’s surprisingly easy.

What’s happening is that GRUB fails to detect the right screen mode, and defaults to one of the lowest available, which is then passed to the Kernel and used by the TTYs. The solution is to tell GRUB what resolution to use, instead of giving it a free hand (to mess it up).

Chobot

ondra@ondrovo.com (Ondřej Hruška) — Wed, 09 Nov 2011 00:00:00 +0000

Chobot is a simple vibrobot with a photo-popper circuit.

To get the required voltage of ~3V, it uses 6 solar cells in series. That’s quite wasteful, but if you have enough cells, why not.

Chobot moves using vibrations generated by spinning an asymmetric weight attached to a motor. It’s not very efficient, but it works - somewhat.

The legs are from some “Kinder Surprise” toy. Motor is from a CD-ROM drive (as usual - I have a good collection of those).

Symet

ondra@ondrovo.com (Ondřej Hruška) — Fri, 26 Jun 2009 00:00:00 +0000

Symet is a breed of beambots that have no logic, but change direction by “tipping over” when they hit something.

Sure enough, my symet doesn’t work as expected. I’m not really sure what I did wrong, but instead of going in a straight line, it goes in circles, and doesn’t “tip over” reliably.

Take this as an example of how not to build a symet ^^

Trainbot

ondra@ondrovo.com (Ondřej Hruška) — Fri, 26 Jun 2009 00:00:00 +0000

This is the first beambot I’ve ever built.

I’m not sure it qualifies as a beambot, but it was built in a similar way.
It’s no engineering masterpiece, all it does is simply moving forward.

Materials used

The energy source is a single 1.5V battery, in a battery socket
Wheels are from old casette deck; they pressed the magnetic tape against the reading head.
The motor comes from an old CD-ROM drive, where it served to eject the tray.
It’s not a cylinder as usual, but flattened on two sides, so it nicely fits there.
The aluminium plating is from some old model-train kit

Design

The whole machine is built around the battery socket. It’s super simple - there are two wheels glued to the bottom of the socket, and a motor in between, with axis pressed against one of them from side. Nothing too fancy or efficient, but does the trick.

Flasher

ondra@ondrovo.com (Ondřej Hruška) — Sun, 14 Jun 2009 00:00:00 +0000

This “flasher” is not an exhibitionist, as you might think from the name.

It’s actually a very simple beambot design, one that just flashes a LED.

The tricky bit is getting enough voltage to light up the diode. If you want to power your bot with solar cells or an AA battery, you will need a step-up converter.

Circuitry

There’s many such converters, a quick Google search will give you some ideas.

Helios

ondra@ondrovo.com (Ondřej Hruška) — Sat, 13 Jun 2009 00:00:00 +0000

This bot, despite having no sensors, avoids shadows and stays in the warm sunlight.

I used no complicated electronics in this build - but you could improve it by adding a photo-popper circuit.

How it works

The trick is simple: Left solar cell powers right motor, and vice versa.

Here’s an illustration of the movement:

Here’s also a very old video of it:

Get a better browser!

Materials used

Solar cells in series (2 per motor - the more, the better)
Two motors from CD-ROM drives (or any other)
A piece aluminium, aluminium foil for the chassis, some plastic to encase the cells.

Here’s a detail from the front:

Spinbot

ondra@ondrovo.com (Ondřej Hruška) — Sat, 13 Jun 2009 00:00:00 +0000

This bot was meant to fly. It spins, at least.

Originally, I’ve attached a plastic propeller to the motor, hung it on a thread and excitedly went to try it in the sun.

It did not work.

Instead of gracefully flying in circles, it kept squirming and spinning around like crazy.

So I’ve attached a cogwheel from a CD-ROM drive and placed it on table - the Spinbot was born.

Kartabot

ondra@ondrovo.com (Ondřej Hruška) — Tue, 12 May 2009 00:00:00 +0000

Kartabot, or “brushbot”, is extremely simple and cute!

If you have the parts and a spare toothbrush, you can make your own in just a few minutes!

Materials

2 solar cells in series
vibration motor from a cell phone
toothbrush

Solar cells are very fragile, it’s just a thin silicon sheet. To fix that, I’ve tinned them on the back side.

Video

Your browser does not support HTML5 video.