Author: Bryan Cockfield

1564 Articles

Button Debouncing With Smart Interrupts

January 4, 2025 by 55 Comments

Debouncing button or switch inputs on microcontrollers can be a challenging problem for those first starting to program these devices. Part of the reason for this difficulty is that real-world buttons don’t behave like the idealized textbook components we first learn about, and therefore need special consideration to operate like one would expect. There are simple ways to debounce inputs like adding a delay after a button is pressed, but for more efficient use of computer resources as well as adding some other capabilities to inputs you might want to look at this interrupt service routine (ISR) method from [Lee] aka [stockvu].

The strategy with this debounce method is not simply to use a single ISR for the button input, but to activate a second timer-based ISR at that time that runs at a certain interval which timestamps any button press and checks the amount of time the button has been active. If it’s under a certain threshold the ISR assumes it’s caused by bounce and blocks the bounce. If the timestamp ages past another longer threshold it knows the button has been released. This method allows on-the-fly adaptation between long button presses and rapid button presses and is capable of debouncing both types.

For those wanting to try this out, [stockyu] has included some example Arduino code for others to use. It’s an interesting take on a solution for a common problem, and puts very little load on the microcontroller. There are about as many ways to debounce inputs as there are microcontroller platforms, though, and you can even use a 555 timer to get this job done which frees up 100% of the microcontroller’s CPU.

Math On A Checkerboard

January 3, 2025 by 3 Comments

The word “algorithm” can sometimes seem like a word designed to scare people away from math classes, much like the words “calculus”, “Fourier transform”, or “engineering exam”. But in reality it’s just a method for solving a specific problem, and we use them all the time whether or not we realize it. Taking a deep dive into some of the ways we solve problems, especially math problems, often leads to some surprising consequences as well like this set of algorithms for performing various calculations using nothing but a checkerboard.

This is actually a demonstration of a method called location arithmetic first described by [John Napier] in 1617. It breaks numbers into their binary equivalent and then uses those representations to perform multiplication, division, or to take the square root. Each operation is performed by sliding markers around the board to form certain shapes as required by the algorithms; with the shapes created the result can be viewed directly. This method solves a number of problems with other methods of performing math by hand, eliminating other methods like trial-and-error. The video’s creator [Wrath of Math] demonstrates all of these capabilities and the proper method of performing the algorithms in the video linked below as well.

While not a “hack” in the traditional sense, it’s important to be aware of algorithms like this as they can inform a lot of the way the world works on a fundamental level. Taking that knowledge into another arena like computer programming can often yield some interesting results. One famous example is the magic number found in the code for the video game Quake, but we’ve also seen algorithms like this used to create art as well.

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Custom Firmware Adds Capabilities To Handie Talkie

January 3, 2025 by 56 Comments

Although ham radio can be an engaging, rewarding hobby, it does have a certain reputation for being popular among those who would fit in well at gated Florida communities where the preferred mode of transportation is the golf cart. For radio manufacturers this can be a boon, as this group tends to have a lot of money and not demand many new features in their technology. But for those of us who skew a bit younger, there are a few radios with custom firmware available that can add a lot of extra capabilities.

The new firmware is developed by [NicSure] for the Tidradio TD-H3 and TD-H8 models and also includes a browser-based utility for flashing it to the radio without having to install any other utilities. Once installed, users of these handheld radios will get extras like an improved S-meter and detection and display of CTCSS tones for repeater usage. There’s also a programmer available that allows the radio’s memory channels to be programmed easily from a computer and a remote terminal of sorts that allows the radio to be operated from the computer.

One of the latest firmware upgrades also includes a feature called Ultra Graph which is a live display of the activity on a selected frequency viewable on a computer screen. With a radio like this and its upgraded firmware, a lot of the capabilities of radios that sell for hundreds of dollars more can be used on a much more inexpensive handheld. All of this is possible thanks to an on-board USB-C interface which is another feature surprisingly resisted by other manufacturers even just for charging the batteries.

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A Modern Battery For A Classic Laptop

January 2, 2025 by 12 Comments

Aside from their ability to operate fairly well in extreme temperatures, lead-acid batteries don’t have many benefits compared to more modern battery technology. They’re heavy, not particularly energy dense, have limited charge cycles, and often can’t be fully discharged without damage or greatly increased wear. With that in mind, one can imagine that a laptop that uses a battery like this would be not only extremely old but also limited by this technology. Of course, in the modern day we can do a lot to bring these retro machines up to modern standards like adding in some lithium batteries to this HP laptop.

Simply swapping the batteries in this computer won’t get the job done though, as lead-acid and lithium batteries need different circuitry in order to be safe while also getting the maximum amount of energy out. [CYUL] is using a cheap UPS module from AliExpress which comes with two 18650 cells to perform this conversion, although with a high likelihood of counterfeiting in this market, the 18650s were swapped out with two that were known to be from Samsung. The USB module also needs to be modified a bit to change the voltage output to match the needs of the HP-110Plus, and of course a modernized rebuild like this wouldn’t be complete without a USB-C port to function as the new power jack.

[CYUL] notes at the end of the build log that even without every hardware upgrade made to this computer (and ignoring its limited usefulness in the modern world) it has a limited shelf life as the BIOS won’t work past 2035. Hopefully with computers like this we’ll start seeing some firmware modifications as well that’ll let them work indefinitely into the future. For modern computers we’ll hope to avoid the similar 2038 problem by switching everything over to 64 bit systems and making other software updates as well.

Handheld Satellite Dish Is 3D Printed

December 23, 2024 by 10 Comments

Ham radio enthusiasts, people looking to borrow their neighbors’ WiFi, and those interested in decoding signals from things like weather satellites will often grab an old satellite TV antenna and repurpose it. Customers have been leaving these services for years, so they’re pretty widely available. But for handheld operation, these metal dishes can get quite cumbersome. A 3D-printed satellite dish like this one is lightweight and small enough to be held, enabling some interesting satellite tracking activities with just a few other parts needed.

Although we see his projects often, [saveitforparts] did not design this antenna, instead downloading the design from [t0nito] on Thingiverse. [saveitforparts] does know his way around a satellite antenna, though, so he is exactly the kind of person who would put something like this through its paces and use it for his own needs. There were a few hiccups with the print, but with all the 3D printed parts completed, the metal mesh added to the dish, and a correctly polarized helical antenna formed into the print to receive the signals, it was ready to point at the sky.

The results for the day of testing were incredibly promising. Compared to a second satellite antenna with an automatic tracker, the handheld 3D-printed version captured nearly all of the information sent from the satellite in orbit. [saveitforparts] plans to build a tracker for this small dish to improve it even further. He’s been able to find some satellite trackers from junked hardware in some unusual places as well. Antennas seem to be a ripe area for 3D printing.

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Dog Plays Chess On ESP32

December 22, 2024 by 10 Comments

The ESP32 is s remarkably powerful microcontroller, where its dual-core processor and relatively high clock speed can do some impressive work. But getting this microcontroller designed for embedded systems to do tasks that would generally be given to a much more powerful PC-type computer takes a little bit more willpower. Inspired by his dog, [Folkert] decided to program an ESP32 to play chess, a famously challenging task for computer scientists in the past. He calls this ESP32 chess system Dog.

One of the other major limitations of this platform for a task like this is memory. The ESP32 [Folkert] is using only has 320 kB of RAM, so things like the transposition table have to fit in even less space than that. With modern desktop computers often having 32 or 64 GB, this is a fairly significant challenge, especially for a memory-intensive task like a chess engine. But with the engine running on the microcontroller it’s ready to play, either in text mode or with something that can use the Universal Chess Interface (UCI). A set of LEDs on the board lets the user know what’s going on while gameplay is taking place.

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Training A Self-Driving Kart

December 21, 2024 by 1 Comment

There are certain tasks that humans perform every day that are notoriously difficult for computers to figure out. Identifying objects in pictures, for example, was something that seems fairly straightforward but was only done by computers with any semblance of accuracy in the last few years. Even then, it can’t be done without huge amounts of computing resources. Similarly, driving a car is a surprisingly complex task that even companies promising full self-driving vehicles haven’t been able to deliver despite working on the problem for over a decade now. [Austin] demonstrates this difficulty in his latest project, which adds self-driving capabilities to a small go-kart.

[Austin] had been working on this project at the local park but grew tired of packing up all his gear when he wanted to work on his machine-learning algorithms. So he took all the self-driving equipment off of the first kart and incorporated it into a smaller kart with a very small turning radius so he could develop it in his shop.

He laid down some tape on the floor to create the track and then set up the vehicle to learn how to drive by watching and gathering data. The model is trained with a convolutional neural network and this data. The only inputs that the model gets are images from cameras at the front of the kart. At first, it could only change the steering angle, with [Austin] controlling the throttle to prevent crashes. Eventually, he gave it control of the throttle as well, which behaves well except at the fastest speeds.

There were plenty of challenges along the way, especially when compared to the models trained at the park; [Austin] correctly theorized that the cause of the hardship in the park was a lack of contrast at the boundary between the track and any out-of-bounds areas. With a few tweaks to the track, as well as adding some wide-angle lenses to his cameras, he was able to get a model that works fairly well. Getting started on a project like this doesn’t have as high of a barrier to entry as one might imagine, either. Take a look at this comprehensive open-source Python library for self-driving projects. If you want to start smaller, perhaps don’t start with a self-driving kart.

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