DIY Wireless Serial Adapter Speaks (True) RS-232

There is a gotcha lurking in wait for hackers who look at a piece of equipment, see a port labeled “Serial / RS-232”, and start to get ideas. The issue is the fact that the older the equipment, the more likely it is to be a bit old-fashioned about how it expects to speak RS-232. Vintage electronics may expect the serial data to be at bipolar voltage levels that are higher than what the typical microcontroller is used to slinging, and that was the situation [g3gg0] faced with some vintage benchtop equipment. Rather than deal with cables and wired adapters, [g3gg0] decided to design a wireless adapter with WiFi and Bluetooth on one end, and true RS-232 on the other.

The adapter features an ESP32 and is attached to a DB-9 plug, so it’s nice and small. It uses the ST3232 chip to communicate at 3 V logic levels on the microcontroller side, supports bipolar logic up to +/-13 V on the vintage hardware side, and a rudimentary web interface allows setting hardware parameters like baud rate. The nice thing about the ST3232 transceiver is that it is not only small, but can work from a 3 V supply with only four 0.1 uF capacitors needed for the internal charge pumps.

As for actually using the adapter, [g3gg0] says that the adapter’s serial port is exposed over TCP on port 23 (Telnet) which is supported by some programs and hardware. Alternately, one can connect an ESP32 to one’s computer over USB, and run firmware that bridges any serial data directly to the adapter on the other end.

Design files including schematic, bill of materials, and PCB design are shared online, and you can see a brief tour of the adapter in the video, embedded below.

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Exploring Op Amp Loading

Op amps are generally pretty easy to apply, but there are some practical nonideal behaviors you have to keep in mind. [EEforEveryone] takes a test board with some 2X amplifiers on it and — after some fiddling around with the scope probes — demonstrates the effect of capacitive loading on the output of an op amp. (Video, embedded below.)

The op amp in question is the OP07. In fact, there are two identical opamps looking at the single input. The output of one op amp feeds directly to the scope probes. The second one passes through a bipolar transistor buffer consisting of an NPN and PNP transistor. Both outputs have optional capacitors that can be jumpered in or out of the circuit.

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Hackaday Links: April 18, 2021

More bad news from Mars this week, and this time not just from Perseverance. Last week the eagerly anticipated first flight of the helicopter Ingenuity was delayed for a couple of days after failing a full-speed spin-up test of its rotors. That appears to have been a bigger deal than initially thought, as it required a significant rewrite of the helicopter’s software. That meant testing, of course, and subsequent upload to the UAV, which at 174 million miles away takes a bit of doing. The good news is that they were able to complete the full-speed rotor test without the full program upload, so we’re one step closer to flight, which may take place as early as Monday morning.

Meanwhile, over at Elysium Planitia, the Mars InSight lander has troubles of its own. The geophysical laboratory, which has been trying to explore the inner structure of Mars since landing in 2018, entered an “emergency hibernation” state this week because of a lack of sufficient power generation. Unlike the radioisotope-powered Perseverance rover, InSight relies on a pair of solar panels for its electricity, and those panels are being obscured by Martian dust. The panels normally get blown clean by Martian winds, but things have been calm lately and the dust has really built up. If this seems like deja vu all over again, it’s probably because a planet-wide dust storm is what killed the plucky Opportunity rover back in 2018. Here’s hoping the wind picks up a little and InSight can get back to work.

Funny what crops up in one’s newsfeed, especially when one is responsible for putting out content that populates others’ newsfeeds. We recently took a look at the dangers of “zinc fever”, a flu-like illness that can crop up after inhaling gasses produced by molten zinc. That resulted in stumbling across an article from last year about mild steel welding fumes being classified as a human carcinogen. This comes from the Health and Safety Executive, a UK government agency concerned with workplace health issues. The release is an interesting read, and it suggests that mild steel fumes can cause not only lung cancer but kidney cancer. The announcement is mainly concerned with British workplaces, of course, but there are some interesting tidbits in there, such as the fact that welding fumes make dust particles so small that they can reach down into the very lowest reaches of lungs, the alveoli where gas exchange occurs. It’s enough to make one invest in PAPR or some kind of fume extractor.

For those of a certain vintage, our first computer was probably something that bore little resemblance to a PC or laptop. It was likely a single-board affair or something like a C64, and acquiring the essential bit of hardware usually left little in the budget for a proper monitor. Little 12″ B&W TVs were a dime a dozen, though, and easily — if grainily — enlisted into service as a monitor by way of an RF modulator. To recreate a little of that magic with modern hardware, Hackaday contributor Adam Zeloof came up with the PiMod Zero, an RF-modulator hat for the Raspberry Pi Zero that turns the component video into an NTSC analog signal. He’s open-sourced the design files, or there’s a CrowdSupply campaign for those who prefer to buy.

And finally, if you somehow traveled back in time to the 1940s with a laptop, how long would it have taken you to crack the Enigma code? Longer than you think, at least according to Dr. Mike Pound over at Computerphile, who released a fascinating video on how Enigma worked and what it took for Turing and the gang at Bletchley to crack the code. We knew some of the details of Enigma’s workings before seeing this video, but Mike’s explanation was really good. And, his explanation of the shortcut method he used to decode an Enigma message made the whole process clearer to us than it’s ever been. Interesting stuff.

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Shapeshifting Streetlights Are The Future We Want To Live In

Regular streetlights are all well and good, bathing us in the glow of their sodium, or more increasingly LED, lamps. They’re mostly rigid metal contraptions installed primarily for public safety purposes. They could be so much more, however, as the Bloomlight demonstrates.

The light consists of a flexible main stem, which can be pulled in different directions by six steel cables controlled by stepper motors. At the top, it has a shroud made of wooden slats and fabric that can bloom like a flower around its central lamp, thanks to a 3D printed mechanism. LIDAR is used to detect approaching humans, at which point the Bloomlight leans over towards them and begins to bloom open, showering them with light.

It’s a beautiful art piece from the Dutch design firm [Vouw], and one we’d love to see in person. The design reminds of this useful tentacle design. With that said, it could grow emotionally exhausting having to repeatedly ignore plaintively waving streetlights that crave human attention as you walk on through the night. Anthropomorphizing anything is usually a double edged sword.

Perhaps the neatest streetlight hack we’ve seen is way back from 2013 – using a laser diode to shut off a streetlight from a distance. Video after the break.

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This Pineapple Keyboard Is The Bomb

Now why didn’t we think of this? While building a dactyl manuform — a semi-ergonomic split keyboard — [dapperrogue] had the life-changing epiphany that keyboards can be any shape or size, as long as there is room for wiring and a microcontroller inside. [dapperrogue]’s first foray into the world of fictional ordnance came in the form of an F-bomb — a round macro keeb made in the classic round explosive shape and covered with function keys. Building on the explosive feedback from that, [dapperrogue] built this bomb of a pineapple keeb, the only anti-personnel factor being the clickiness of the key switches.

This groovy grenade has 25 keys total, 24 of which are in a 4×6 grid around the body. The 25th key, the best one, is hiding under the lever and you bet it can only be actuated by pulling the pin first. We love the use of the lever because it makes us think of Morse code keyers, which might be what we would use that switch for.

Inside is an Arduino Pro Micro running QMK and some skillful wiring. The entirely 3D-printed enclosure is in two main pieces that are connected with M3 screws, plus the top. If you want to pack one of your own, the STLs and firmware are out on GitHub. Just don’t take it to the airport.

Be sure to check out the demos after the break — in the stock firmware, every key types out a different onomatopoeic boom-type sound. Are you more of a pacifist when it comes to macro pad design? That’s understandable. We have plenty of different builds to admire.

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Bridging The PC And Embedded Worlds With Pico And Python

Although protocols like I2C and SPI are great for communicating between embedded devices and their peripherals, it can be a pain to interface these low-level digital interfaces to a PC. [Alexandre] typically used an Arduino to bridge between the PC and embedded worlds, but he got tired of defining a custom serial protocol for each project. Inspired by MicroPython’s machine module, [Alexandre] has developed u2if—an implementation of some of MicroPython’s machine module for PC—using a USB-connected Raspberry Pi Pico to bridge between a PC and low-level digital interfaces.

u2if consists of two parts: the PC portion is a Python implementation of a portion of the MicroPython machine module, and the Raspberry Pi Pico receives some custom C++ firmware. Thus far, [Alexandre] has implemented functionality for the onboard ADCs, I2C, SPI, UART, and GPIO lines as well as additional support for I2S sound and the WS2812B addressable LED.

Development board for Raspberry Pi Pico.

In addition to the u2if package, [Alexandre] has designed a PCB to break out all of the Raspberry Pi Pico’s interfaces in a handy 3×3.9″ board. We especially like that multiple headers are supplied for I2C, including one with enough space to mount an SSD1306 OLED display.

We think this could be an incredibly useful tool, and what makes it even more impressive is that it uses a board many of us already have laying around. If you want a dedicated device for interfacing with low-level digital buses, you may want to check out the GreatFET.

Toggle Switch Puzzle Boggles The Mind, Opens The Box

We all have too much stock of one component or another. Maybe you have more audio pots than you know what to do with, or maybe it’s zener diodes. For [technologyguy], that thing is a pile of toggle switches.  Fortunately he’s always wanted to build a locking box with a binary code that’s laid out in switches — as in, find the right code, and a solenoid unlatches the box. This lovely parts bin special only responds to two combinations out of a possible 4,000+, so anyone who tries to open it should probably block out the afternoon.

Inside you’ll find two 9 V batteries, a home-brew metal latch, a solenoid, and the undersides of four DPDT and eight SPDT toggle switches. If you just picked this thing up and had no idea what was going on, you’d be so screwed as to what to do first. The box needs power, so you’d have to figure out which switch is which. But it’s so much harder than that, because the bottom left switch selects between the two paths that result in an unlocked book-box.

The next two toggles in from the left are on/off selectors for code A and code B, so not only do you have to have the right path chosen, you have to power it, too. The only progress indicators are the LEDs — there’s one for main power, and the other lets you know that the box is unlatched. What a fun conversation piece for the coffee table Zoom-viewable area!

Want to do something far less useful with your throng of toggles? How about a complicated useless machine?