Two hands holding a 3d printed alarm clock with an LCD display, snooze button and knob on top

IO Connected Radio Alarm Clock

December 19, 2022 by Abe Connelly 3 Comments

[CoreWeaver] creates an alarm clock that includes features one might expect in such a project, including an FM radio, snooze button inputs and a display, but goes beyond the basic functionality to include temperature sensing and a PC connection, opening the way for customizable functionality.

An Atmega328 is used for the main microcontroller which communicates via I2C both to a DS1307 real time clock (RTC) and a TEA5767 FM module. The main power comes from a 9V power source with an LM317 and LM7805 linear regulators providing a 3.3V and 5V power rail, respectively. Most of the electronics are powered using 5V except for the TEA5767, which is powered from the 3.3V rail and has its I2C communication levels shifted from 5V to 3.3V. The audio output of the TEA5767 feeds directly into the TDA7052 audio amplifier to drive the speakers. Since the RTC has an auxiliary coin cell battery for power, the alarm clock can keep accurate time even when not plugged in. Continue reading “IO Connected Radio Alarm Clock” →

Minimal Tic Tac Toe Business Card

September 24, 2022 by Stephen Ogier 38 Comments

The PCB business card has long been a way for the aspiring electronics engineer to set themself apart from their peers. Handing out a card that is also a two player game is a great way to secure a couple minutes of a recruiter’s time, so [Ryan Chan] designed a business card that, in addition to his contact information, also has a complete Tic-Tac-Toe game built in.

[Ryan] decided that an OLED display was too expensive for something to hand out and an LED matrix too thick, so he decided to keep it simple and use an array of 18 LEDs—9 in each of two colors laid out in a familiar 3×3 grid. An ATmega328p running the Arduino bootloader serves as the brains of the operation. To achieve a truly minimal design [Ryan] uses a single SMD pushbutton for control: a short press moves your selection, a longer press finalizes your move, and a several-second press switches the game to a single-player mode, complete with AI.

If you’d like to design a Tic-Tac-Toe business card for yourself, [Ryan] was kind enough to upload the schematics and code for his card. If you’re still pondering what kind of PCB business card best represents you, it’s worth checking out cards with an updatable ePaper display or a tiny Tetris game.

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The Inner Machinations Of The Arduino Are An Enigma

September 19, 2022 by Bryan Cockfield 88 Comments

Arduinos have been the microcontroller platform of choice for nearly two decades now, essentially abstracting away a lot of the setup and lower-level functions of small microcontrollers in favor of sensible IDEs and ease-of-use. This has opened up affordable microcontrollers to people who might not be willing to spend hours or days buried in datasheets, but it has also obscured some of those useful lower-level functions. But if you want to dig into them, they’re still working underneath everything as [Jim] shows us in this last of a series of posts about interrupts.

For this how-to, [Jim] is decoding linear timecodes (LTCs) at various speeds. This data is usually transmitted as audio, so the response from the microcontroller needs to be quick. To make sure the data is decoded properly, the first thing to set up is edge detection on the incoming signal. Since this is about using interrupts specifically, a single pin on the Arduino is dedicated to triggering an interrupt on these edges. The rest of the project involves setting up an interrupt service routine, detecting the clock signal, and then doing all of the processing necessary to display the received LTC on a small screen.

The project page goes into great detail about all of this, including all of the math that needs to be done to get it set up correctly. As far as general use of interrupts goes, it’s an excellent primer for using the lower-level functionality of these microcontrollers. And, if you’d like to see the other two projects preceding this one they can be found on the first feature about precision and accuracy, and the second feature about bitbanging the protocol itself.

Diagram of the LTC protocol, showing the difference between 1 bits and 0 bits - both transmitted using one up and one down pulse, but with '1' bit pulses being half as short.

Animate Arcane Protocols With Interrupt-Backed Bitbanging

June 19, 2022 by Arya Voronova 10 Comments

We often take our “SoftwareSerial” libraries for granted, and don’t investigate what goes on under the hood — until they fail us, at least. Would you like to learn how to harness the power of interrupt-driven bitbanging? [Jim Mack] teaches us how to make our protocol implementations fly using the LTC protocol as a springboard.

LTC (Linear/[Longitudinal] TimeCode) is a widely-used and beautifully-crafted protocol that tends to fly under our radar, and is one that hackers could learn plenty from. It’s used for synchronization of audio/video devices during media production and playback. LTC’s signal is almost digital but not quite: it doesn’t need a clock, and it has no polarity. Additionally, it mimics an audio signal really well, you can decode it at any playback speed, and many other benefits and quirks that [Jim] outlines. You do need to maintain the timings, though, and [Jim]’s article shows us how to keep them right while not inconveniencing your primary tasks.

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A graph visualising approximation errors - the specific principle pictured is described well by the linked article

Time And Accuracy In Las ATMegas

January 31, 2022 by Arya Voronova 4 Comments

Do you ever have to ensure that an exact amount of time passes between two tasks in your microcontroller code? Do you know what’s the difference between precision and accuracy? Today, [Jim Mack] tells us about pushing timers and interrupts to their limits when it comes to managing time, while keeping it applicable to an ever-popular ATMega328P target! Every now and then, someone decides to push the frontiers of what’s possible on a given platform, and today’s rules is coding within constraints of an Arduino environment. However, you should check [Jim]’s post out even if you use Arduino as a swearword – purely for all of the theoretical insights laid out, accompanied by hardware-accurate examples!

This will be useful to any hacker looking to implement, say, motor encoder readings, signal frequency calculations, or build a gadget processing or modifying audio in real time. To give you a sample of this article, [Jim] starts by introducing us to distinctions between precision and accuracy, and then presents us with a seemingly simple task – creating exactly 2400 interrupts a second. As much as it might look straightforward, problems quickly arise when clock crystal frequency doesn’t cleanly divide by the sampling frequency that you have to pick for your application! This is just a taste of all the examples of hidden complexity presented, and they’re accompanied with solutions you can use when you eventually encounter one of these examples in your hacker pursuits. In the end, [Jim] concludes with links to other sources you can study if you ever need to dig deeper into this topic.

Keeping our projects true to the passage of time can be an issue, and we’ve been at it for ages – calibrating your RC oscillator is a rite of passage for any ATTiny project. If you ever decide to have an interrupt peripheral help you with timing issues, we’ve gone in-depth on that topic in the past, with a three-part series describing the benefits, the drawbacks and the edgecases of interrupts. Going for a more modern target? Our piece on using interrupts with STM32 is a great path for trying out tools of the modern age.

Arduino Compatible IR Blaster Keeps TVs At Bay

June 8, 2021 by Tom Nardi 39 Comments

The TV-B-Gone is a well known piece of kit in hacker circles: just point it at a noisy TV in a public space, hit the button, and one of the hundreds of IR remote codes for “Power Off” that it blinks out in rapid succession is more than likely to get the intended response. Unfortunately, while a neat conversation starter, its practical use is limited to a single function. But not so with this programmable IR development board that creator [Djordje Mandic] describes as a “TV-B-Gone on steroids”.

Sure you can point it at a random TV and turn it off with a single button press, but you can also plug the board into your computer and control it directly through the serial connection provided by its CP2104 chip. Using a simple plain-text control protocol, the user can modify the behavior of the device and monitor its status. [Djordje] imagines this feature being used in conjunction with a smartphone application for covert applications. To that end, the device’s support for an onboard battery should keep it from draining the phone during extended operations.

Of course you could do something else entirely with it simply by firing up the Arduino IDE and writing some new code for the device’s ATmega328P microcontroller. As with the IR-enabled ESP8266 development board we looked at a few months ago, there are plenty of applications for an all-in-one board that allows you to communicate with the wide world of IR devices.

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Build-It-Yourself LC Meter

March 22, 2021 by Stephen Ogier 31 Comments

A basic digital multimeter (DMM) is usually the first measurement tool the aspiring electronics tinkerer buys. Even a bargain-bin DMM will happily measure voltage, current, and resistance; check continuity; and may even have a mode to measure transistor gain. Every toolbox needs at least one DMM, but most have an crucial limitation— they can’t measure two of the fundamental electrical quantities: inductance and capacitance. On Hackaday.io, [core weaver] has developed an open-source LC meter to allow you to build your own tool to measure inductance and capacitance.

[core weaver]’s design is all through-hole, so even just assembling one would be a great exercise for someone getting started in electronics. However, he didn’t just release a design, in a series of videos he goes through the theory of the device’s operation; explains the design of the circuit, firmware, and case; and shows you how to put it all together. For times when you need to measure a lot of parts (e.g. if you have to sort a bag of cheap capacitors looking for specific value), he’s even developed a desktop program to save you some trouble!

The finished meter looks incredible! If you want to build one for yourself, he’s put all of the files up on GitHub, and we highly recommend you check out his first video after the break. If you’d like to build yourself a 6.5-digit DMM to go with our LC Meter, consider this one which even has a home-built ADC.

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