Hackaday Links: June 14, 2020

You say you want to go to Mars, but the vanishingly thin atmosphere, the toxic and corrosive soil, the bitter cold, the deadly radiation that sleets down constantly, and the long, perilous journey that you probably won’t return from has turned you off a little. Fear not, because there’s still a way for you to get at least part of you to Mars: your intelligence. Curiosity, the Mars rover that’s on the eighth year of its 90-day mission, is completely remote-controlled, and NASA would like to add some self-driving capabilities to it. Which is why they’re asking for human help in classifying thousands of images of the Martian surface. By annotating images and pointing out what looks like soil and what looks like rock, you’ll be training an algorithm that one day might be sent up to the rover. If you’ve got the time, give it a shot — it seems a better use of time than training our eventual AI overlords.

We got a tip this week that ASTM, the international standards organization, has made its collection of standards for testing PPE available to the public. With titles like “Standard Test Method for Resistance of Medical Face Masks to Penetration by Synthetic Blood (Horizontal Projection of Fixed Volume at a Known Velocity)”, it seems like the standards body wants to make sure that that homebrew PPE gets tested properly before being put into service. The timing of this release is fortuitous since this week’s Hack Chat features Hiram Gay and Lex Kravitz, colleagues from the Washington University School of Medicine who will talk about what they did to test a respirator made from a full-face snorkel mask.

There’s little doubt that Lego played a huge part in the development of many engineers, and many of us never really put them away for good. We still pull them out occasionally, for fun or even for work, especially the Technic parts, which make a great prototyping system. But what if you need a Technic piece that you don’t have, or one that never existed in the first place? Easy — design and print your own custom Technic pieces. Lego Part Designer is a web app that breaks Technic parts down into five possible blocks, and lets you combine them as you see fit. We doubt that most FDM printers can deal with the fine tolerances needed for that satisfying Lego fit, but good enough might be all you need to get a design working.

Chances are pretty good that you’ve participated in more than a few video conferencing sessions lately, and if you’re anything like us you’ve found the experience somewhat lacking. The standard UI, with everyone in the conference organized in orderly rows and columns, reminds us of either a police line-up or the opening of The Brady Bunch, neither of which is particularly appealing. The paradigm could use a little rethinking, which is what Laptops in Space aims to do. By putting each participant’s video feed in a virtual laptop and letting them float in space, you’re supposed to have a more organic meeting experience. There’s a tweet with a short clip, or you can try it yourself. We’re not sure how we feel about it yet, but we’re glad someone is at least trying something new in this space.

And finally, if you’re in need of a primer on charlieplexing, or perhaps just need to brush up on the topic, [pileofstuff] has just released a video that might be just what you need. He explains the tri-state logic LED multiplexing method in detail, and even goes into some alternate uses, like using optocouplers to drive higher loads. We like his style — informal, but with a good level of detail that serves as a jumping-off point for further exploration.

Returning Digital Watches To The Analog Age: Enter The Charliewatch

The Charliewatch by [Trammell Hudson] is one of those projects which is beautiful in both design and simplicity. After seeing [Travis Goodspeed]’s GoodWatch21 digital watch project based around a Texas Instruments MSP430-based SoC, [Trammell] decided that it’d be neat if it was more analog. This is accomplished using the CC430F5137IRGZR (a simpler member of the MSP430 family) and a whole bunch of 0603 SMD LEDs which are driven using Charlieplexing.

This time-honored method of using very few I/O pins to control many LEDs makes it possible to control 72 LEDs without dedicating 72 pins. The density makes animations look stunning and the digital nature melts away leaving a distinct analog charm.

A traditional sapphire crystal was sourced from a watchmaker for around 14€ as was the watch band itself. The rest is original work, with multiple iterations of the 3D printed case settling in on a perfect fit of the crystal, PCB, and CR2032 coin cell stackup. The watch band itself hold the components securely in the housing, and timekeeping is handled by a 32.768 kHz clock crystal and the microcontroller’s RTC peripheral.

The LEDs can be seen in both daylight and darkness. The nature of Charlieplexing means that only a few of the LEDs are ever illuminated at the same time, which does wonders for battery life. [Trammell] tells us that it can run for around six months before the coin cell needs replacing.

It’s completely open source, with project files available on the project’s Github page. We hope to see an army of these watches making appearances at all upcoming electronics-oriented events. Just make sure you lay off the caffeine as the process of hand-placing all those LEDs looks daunting.

Tucoplexing: A New Charliplex For Buttons And Switches

Figuring out the maximum number of peripherals which can be sensed or controlled with a minimum number of IOs is a classic optimization trap with a lot of viable solutions. The easiest might be something like an i2c IO expander, which would give you N outputs for 4 wires (SDA, SCL, Power, Ground). IO expanders are easy to interface with and not too expensive, but that ruins the fun. This is Hackaday, not optimal-cost-saving-engineer-aday! Accordingly there are myriad schemes for using high impedance modes, the directionality of diodes, analog RCs, and more to accomplish the same thing with maximum cleverness and minimum part cost. Tucoplexing is the newest variant we’ve seen, proven out by the the prolific [Micah Elizabeth Scott] (AKA [scanlime]) and not the first thing to be named after her cat Tuco.

[Micah’s] original problem was that she had a great 4 port USB switch with a crummy one button interface. Forget replacement; the hacker’s solution was to reverse and reprogram the micro to build a new interface that was easier to relocate on the workbench. Given limited IO the Tucoplex delivers 4 individually controllable LEDs and 4 buttons by mixing together a couple different concepts in a new way.

Up top we have 4 LEDs from a standard 3 wire Charlieplex setup. Instead of the remaining 2 LEDs from the 3 wire ‘plex at the bottom we have a two button Charlieplex pair plus two bonus buttons on an RC circuit. Given the scary analog circuit the scan method is pleasingly simple. By driving the R and T lines quickly the micro can check if there is a short, indicating a pressed switch. Once that’s established it can run the same scan again, this time pausing to let the cap charge before sensing. After releasing the line if there is no charge then the cap must have been shorted, meaning that switch was pressed. Else it must be the other non-cap switch. Check out the repo for hardware and firmware sources.

Last time we talked about a similar topic a bunch of readers jumped in to tell us about their favorite ways to add more devices to limited IOs. If you have more clever solutions to this problem, leave them below! If you want to see the Twitter thread with older schematics and naming of Tucoplexing look after the break.

Continue reading “Tucoplexing: A New Charliplex For Buttons And Switches”

Get Twelve Charlieplexed PWM Outputs From An ATtiny85

Most of us are aware that charlieplexing can drive a large number of LEDs from a relatively small number of I/O pins, but [David Johnson-Davies] demonstrates adding another dimension to that method to create individually controlled PWM outputs as well. His ATtiny85 has twelve LEDs, each with individually-set brightness levels, and uses only four of the five I/O pins on the device.

Each LED can be assigned a brightness between 0 (fully off) and 63 (fully on). The PWM is done by using one of the timers in the ATtiny85 to generate a periodic interrupt, and the ISR for the interrupt takes care of setting the necessary ratios of on and off times for each charlieplexed output. The result? Twelve flicker-free LEDs with individually addressable brightness levels, using an 8-pin microcontroller and just a few passive components on a tiny breadboard. There’s even one I/O pin left on the ATtiny85, for accepting commands or reading a sensor.

[David] really wrings a lot out of the ATtiny series of microcontrollers with his compact projects, like his Tiny Function Generator (which recently got an update.) He also demonstrated that while charlieplexing is usually used with LEDs, charlieplexing can be used with switches just as easily.

Building And Controlling 19 LEDs & Five Buttons From Five Outputs

Numbers are hard enough in English, but [Sadale] decided to take things a step further by building a calculator that works in Toki Pona. The result is Ilo Nanpa, an awesome hardware calculator that works in this synthetic minimal language. This is a bit harder than you might think, because Toki Pona doesn’t have digits in the same way that Neo-Latin languages like English do. Instead, you combine smaller numbers to make bigger ones. One is Wan, Two is Tu, but three is Wan Tu (1+2). As you might expect, this makes dealing and representing larger numbers somewhat complicated.

Ilo Nanpa gets around this in a wonderfully elegant way, and with some impressive behind the scenes work. The calculator has 16 LEDs, nine buttons and a slider switch, but they are all controlled and read through just five IO pins on the STM8S001J3 controller that runs the device.

That’s because {Sadale] did some remarkable work with multiplexing and charlieplexing. Multiplexing is controlling more outputs than there are control inputs by using rows and columns: it is how the LED display you are probably reading this on can be controlled by just a few wires. By switching through these rows and columns at a higher speed than the eye can see, you create the illusion of a single, continuous display.

Charlieplexing takes this a step further by using multiple voltages on a single connection to further split the signal. With the clever use of voltage dividers the directional properties of LEDs and multiple voltage levels, the Ilo Nanpa runs all of the LEDs and senses all of the buttons and the slider from just five pins. That’s a remarkably neat piece of design, and it is worth spending some time looking over the excellent explanation of the process that [Sadale] wrote to see how it is done, and poring over the code for the device to see how he programmed this all into a single low powered chip. And, while you are reading, you might pick up a few words of Toki Pona. Tawa Pona!

Continue reading “Building And Controlling 19 LEDs & Five Buttons From Five Outputs”

Less Is More: A Micromatrix Display In A Square Inch

In your living room, the big display is what you want. But in an embedded project, often less is more. We think [bobricius] will agree since he submitted a tiny 4×5 LED display into our square inch challenge. The board features an ATtiny CPU and twenty SMD LEDs in a nice grid. You can see them in action, scrolling to some disco music in the video below.

There is plenty of room left in the CPU for bigger text strings — the flash memory is just over 10% full. A little side-mounted header makes it easy to program the chip if you want to change anything.

Continue reading “Less Is More: A Micromatrix Display In A Square Inch”

Minimum Viable 1-D PONG

What makes a game a game? Like, how do we know that we’re looking at a variation of PONG when confronted with one? And how do we know how to play it? [Bertho] sought to answer this question as he designed what is probably the smallest-ever 1-D PONG game. His answer involves charlieplexing LEDs, using a voltage divider to save I/O pins, and a couple of AAAs that should last for a long, long time.

[Bertho]’s Minimum 1-D PONG, or m1dp for short, puts an ATTiny85 through its paces as gameplay quickly progresses from ‘I got this’ to ‘no one could possibly keep this up’. This state machine sleeps until one of the two buttons is pressed, at which time a wait animation starts. The action begins with the next button press.

Game play across only five LEDs makes for some pretty intense action, too. Fortunately, the buzzer is a big part of the experience. It sounds one tone for each LED when the ball is in play, and a different tone to confirm button presses. [Bertho] saved so many I/O pins with charlieplexing that he added a green LED that lights up when it’s OK to return the ball. If we were playing, we’d keep our eye on this LED instead of trying to watch the ball. We’re serving the demo after the break point, so don’t let it get past you.

For a study in minimalism, there sure is a lot going on here with all the different tones and animations. If you’d prefer maximalist 1-D PONG, there’s always LED strips. If dungeon crawlers with satisfying hardware are more your thing, you really need to check out Twang.

Continue reading “Minimum Viable 1-D PONG”