Microcontrollers

2241 Articles

An Impeccably Designed High-Speed LED Flash

May 16, 2019 by 58 Comments

If you want to take a picture of something fast, and we mean really fast, you need to have a suitably rapid flash to illuminate it. A standard camera flash might be good enough to help capture kids running around the back yard at night, but it’s not going to do you much good if you’re trying to get a picture of a bullet shattering a piece of glass. For that you’ll need something that can produce microsecond flashes, allowing you to essentially “freeze” motion.

You can buy a flash that fast, but they aren’t common, and they certainly aren’t cheap. [td0g] thought he could improve on the situation by developing his own microsecond flash, and he was kind enough to not only share it with the world, but create a fantastically detailed write-up that takes us through the entire design and construction process. Even if you aren’t in the market for a hyper-fast flash for your camera, this is a fascinating look at how you can build an extremely specialized piece of gear out of relatively common hardware components.

So what goes into a fast LED flash? Rather unsurprisingly, the build starts with high-quality LEDs. After some research, [td0g] went with an even dozen CREE CXA2530 arrays at just shy of $7 USD each. Not exactly cheap, but luckily the rest of the hardware is pretty garden variety stuff, including a ATMega328P microcontroller, some MOSFETs, and a TC4452 driver. He did pack in some monstrous 400 V 10μf capacitors, but has since realized they were considerably overkill and says he would swap them out if doing it all over again.

To make development easier (and less costly, should anything go wrong), [td0g] designed the flash so that the LEDs are arranged in banks of three which can be easily removed or swapped in the 3D printed case. Each trio of LEDs is in a removable “sled” that also holds the corresponding capacitor and MOSFET. Then it was just a matter of getting the capacitors charged up and safely dumping their energy into the banks of LEDs without frying anything. Simple.

At this point, the astute reader is probably thinking that a high speed flash is worthless without an equally fast way of triggering it. You’d be right, but [td0g] already figured that part. A couple years back we covered his incredible ballistic chronometer which is being used as a sensor to fire off his new flash.

Bare Metal Programming With Only Three Buttons

May 12, 2019 by 28 Comments

For anyone who’s seen a 1970’s era microcomputer like the Altair 8800 doing its thing, you’ll know the centerpiece of these behemoths is the array of LEDs and toggle switches used as input and output. Sure, computers today are exponentially more capable, but there’s something undeniably satisfying about developing software with pen, paper, and the patience to key it all in.

If you’d like to get a taste of old school visceral programming, but aren’t quite ready to invest in a 40 year old computer, then [GClown25] might have the answer for you. He’s developed a pocket sized “computer” he’s calling the BIT4 that can be programmed with just three tactile switches. In reality it’s an ATMega4809 running C code, but it does give you an idea of how the machines of yesteryear were programmed.

In the video after the break, [GClown25] demonstrates the BIT4 by entering in a simple binary counter program. With a hand-written copy of the program to use as a reference, he steps through the memory addresses and enters in the command and then the value he wishes to operate on. After a few seconds of frantic button pushing, he puts the BIT4 into run mode and you can see the output on the array of LEDs along the top edge of the PCB.

All of the hardware and software is open source for anyone who’s interested in building their own copy, or perhaps just wants to take a peak at how [GClown25] re-imagined the classic microcomputer experience with modern technology. Conceptually, this project reminds us of the Digirule2, but we’ve got to admit the fact this version isn’t a foot long is pretty compelling.

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This Atomic Pi Eats Other Pis For Lunch

May 8, 2019 by 102 Comments

The world is full of single board computers that want a slice of the Raspberry Pi action. Most of them are terrible. But fools and their money, yadda yadda, and there’s a new sucker born every minute. The latest contender to the Raspberry Pi is the Atomic Pi. It’s an x86-based single board computer that costs $35, shipped to your door. Is it worth it? Is it even in the same market as a Raspberry Pi? Or is it just a small budget computer without a box? I have no idea.

With that said, the Atomic Pi comes with an Intel Atom x5-Z8350 with Intel HD Graphics (Cherry Trail). There is 2 GB of DDR3L-16000, 16 GB of eMMC, and an SD slot for storage. Connectivity is a full HDMI port (primary audio out), USB 3.0 and 2.0 ports, a Mediatec RT5572 used for WiFi, a Qualcomm CSR8510 for Bluetooth 4.0, a “Legitimate licensed BIOS”, and a real-time clock. Overall, you’re looking at a top-of-the-line tablet computer from four years ago. One that would run Windows.

To use all the features of the Atomic Pi, you will need to buy a $15 breakout board to supply power to the board, and use a large industrial power supply, the kind you would normally find bolted to a RepRap or a homemade CNC machine. You will need to supply both 5 V and 12 V to the board if you would like to use the Class D audio amplifier, but if you only want to use audio over HDMI, supplying only 5 V will do. If you want to boot this board, it looks like you’ll need to bring a USB/TTL cable to make everything work. This may be a tough sell to a crowd with zero experience booting a bare Linux system. That said, it runs Nintendo 64 emulators well, which is the only reason people buy Raspberry Pis anyway.

Is the Atomic Pi the single board computer you need? I don’t know. But we’ve got an Atomic Pi on order, and we’re ready to go with a full review when it show up.

Play Tetris On A Transistor Tester, Because Why Not?

May 3, 2019 by 4 Comments

[Robson] had been using the same multimeter since he was 15. It wasn’t a typical multimeter, either. He had programmed it to also play the Google Chrome jumping dinosaur game, and also used it as a badge at various conferences. But with all that abuse, the ribbon cable broke and he set about on other projects. Like this transistor tester that was just asking to have Tetris programmed onto its tiny screen.

The transistor tester is a GM328A made for various transistor testing applications, but is also an LCR meter. [Robson]’s old meter didn’t even test for capacitance but he was able to get many years of use out of that one, so this device should serve him even better. Once it was delivered he set about adding more features, namely Tetris. It’s based on an ATmega chip, which quite easy to work with (it’s the same chip as you’ll find in the Arduino Uno but [Robson’s] gone the Makefile route instead of spinning up that IDE). Not only did he add more features, but he also found a mistake in the frequency counter circuitry that he fixed on his own through the course of the project.

If you’ve always thought that the lack of games on your multimeter was a total deal breaker, this project is worth a read. Even if you just have a random device lying around that happens to be based on an ATmega chip of some sort, this is a good primer of getting that device to do other things as well. This situation is a fairly common one to be in, too.

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How-To: Mapping Server Hits With ESP8266 And WS2812

May 2, 2019 by 17 Comments

It has never been easier to build displays for custom data visualization than it is right now. I just finished one for my office — as a security researcher I wanted a physical map that will show me from where on the planet my server is being attacked. But the same fabrication techniques, hardware, and network resources can be put to work for just about any other purpose. If you’re new to hardware, this is an easy to follow guide. If you’re new to server-side code, maybe you’ll find it equally interesting.

I used an ESP8266 module with a small 128×32 pixel OLED display connected via an SSD1306 controller. The map itself doesn’t have to be very accurate, roughly knowing the country would suffice, as it was more a decorative piece than a functional one. It’s a good excuse to put the 5 meter WS2812B LED strip I had on the shelf to use.

The project itself can be roughly divided into 3 parts:

  1. Physical and hardware build
  2. ESP8266 firmware
  3. Server-side code

It’s a relatively simple build that one can do over a weekend. It mashes together LED strips, ESP8266 wifi, OLED displays, server-side code, python, geoip location, scapy, and so on… you know, fun stuff.

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FemtoBeacon Is A Tiny ESP32 Coin-Shaped Dev Board

April 28, 2019 by 21 Comments

Our single board microcontroller platforms have become smaller over the years, from the relatively large classic Arduino and Beagleboard form factors of a decade ago to the postage stamp sized Feather and ESP boards of today. But just how small can they go? With current components, [Femtoduino] think they’ve cracked it, delivering an ESP32-based board with WiFi and Bluetooth, and an LDO regulator for 5 V operation in a circular footprint that’s only 9 mm in diameter.

There are some compromises from such a paucity of real-estate, of which perhaps the most obvious is a lack of space to make I/O lines available. It has SPI, a UART, and a couple of I/O lines, and aside from an onboard RGB LED that’s it. But SPI is versatile well beyond its number of lines, and even with so little there is much that can be done. Another potential compromise comes from the antenna, a Molex surface-mount component, which is an inevitable consequence of a 9 mm circular board.

There has to come a point at which a microcontroller platform becomes so small as to be unusable, but it’s clear that there is a little further for this envelope to be pushed. We’d love to see what other designers do in response to this board.

All You Need To Know About I2S

April 18, 2019 by 24 Comments

Last month we marked the 40th birthday of the CD, and it was as much an obituary as a celebration because those polycarbonate discs are fast becoming a rarity. There is one piece of technology from the CD age that is very much still with us though, and it lives on in the standard for sending serial digital audio between chips. The protocol is called I2S and comes as a hardware peripheral on many microcontrollers. It’s a surprisingly simple interface that’s quite easy to work with and thus quite hackable, so it’s worth a bit of further investigation.

It’s A Simple Enough Interface

Don’t confuse this with the other Philips Semiconductor protocol: I2C. Inter-Integrated Circuit protocol has the initials IIC, and the double letter was shortened to come up with the “eye-squared-see” nomenclature we’ve come to love from I2C. Brought to life in 1982, this predated I2S by four years which explains the somewhat strange abbreviation for “Inter-Integrated Circuit Sound”.

The protocol has stuck around because it’s very handy for dealing with the firehose of serial data associated with high-quality digital audio. It’s so handy that you’ve likely heard of it being used for other purposes than audio, which I’ll get to in a little bit. But first, what does I2S actually do?

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