Audio Out Over A UART With An FTDI USB-To-TRS Cable

February 24, 2021 by Maya Posch 41 Comments

What is the easiest way to get audio from a WAV file into a line-level format, ready to be plugged into the amplifier of a HiFi audio set (or portable speaker)? As [Konrad Beckmann] demonstrated on Twitter, all you really need is a UART, a cable and a TRS phono plug. In this case a USB-TTL adapter based around the FTDI FT232R IC: the TTL-232R-3V3-AJ adapter with 12 Mbps USB on one end, and a 3 Mbps UART on the other end.

[Konrad] has made the C-based code available on GitHub. Essentially what happens underneath the hood is that it takes in a PCM-encoded file (e.g. WAV). As a demonstration project, it requires the input PCM files to be a specific sample rate, as listed in the README, which matches the samples to the baud rate of the UART. After this it’s a matter of encoding the audio file, and compiling the uart-sound binary.

The output file is the raw audio data, which is encoded in PDM, or Pulse-Density Modulation. Unlike Pulse-Code Modulation (PCM), this encoding method does not encode the absolute sample value, but uses binary pulses, the density of which corresponds to the signal level. By sending PDM data down the UART’s TX line, the other side will receive these bits. If said receiving device happens to be an audio receiver with an ADC, it will happily receive and play back the PDM signal as audio. As one can hear in the video embedded in the tweet, the end result is pretty good.

If we look at at the datasheet for the TTL-232R-3V3-AJ adapter cable, we can see how it is wired up:

When we compare this to the wiring of a standard audio TRS jack, we can see that the grounds match in both wirings, and TX (RX on the receiving device) would match up with the left channel, with the right channel unused. A note of caution here is also required: this is the 3.3V adapter version, and it lists its typical output high voltage as 2.8V, which is within tolerances for line-level inputs. Not all inputs will be equally tolerant of higher voltages, however.

Plugging random TRS-equipped devices into one’s HiFi set, phone or boombox is best done only after ascertaining that no damage is likely to result. Be safe, and enjoy the music.

Launching An Open Source Keyboard; System76 Has Published Their Design Files

February 20, 2021 by Kerry Scharfglass 46 Comments

System76, a computer manufacturer known for selling machines which run Linux, recently unveiled the complete sources for their forthcoming Launch mechanical keyboard. Made with familiar tools, mass produced, and backed by a stable company it looks like the Launch will be a compelling entrant into the world of mechanical keyboards.

Back in March of 2020 System76 published a blog post about a new project they were embarking on; a mechanical keyboard with an unusual layout. At the time there was scant information available besides a summer 2021 target and little was heard until last week when they opened up access to the Launch repository. Everything should be recognizable if you’ve ever looked at the sources for a customized mechanical keyboard before, which is what gets our attention. Electrical sources are authored with KiCad and should be easy to tweak or fabricate. And mechanical components are provided in STEP files with mechanical drawings, presumably because they intend to actually manufacture these.

Feature wise all the usual hallmarks of a well designed keyboard are here. The Launch uses hostswap sockets to make it easy to install the usual Cherry MX compatible switch options, and includes per-key RGB backlighting courtesy of SK6805 LEDs. The ATmega32U4 runs the popular and extremely capable QMK firmware instead of something bespoke, so it should be easy to customize to the user’s desire.

System76 touts an unusual key layout, but if you’ve seen a 75% keyboard before it shouldn’t be too threatening (though we do wonder about that shrunken right shift). The most unusual feature is that it features a USB hub capable of full speed 10 gigabit USB 3.1 Gen 2 on two USB-C and two USB-A ports. It’s worth checking out the schematic to appreciate how much more complicated the hub design is than the rest of the keyboard, which is practically vestigial in comparison.

The remaining unknown is how the Launch integrates with Pop!_OS, System76’s awkwardly named remix of Ubuntu. They promise deep, compelling integration and we’re excited to see how that manifests.

Dynamic Macro Keyboard Controls All The Things

February 18, 2021 by Kristina Panos 8 Comments

Keyboard shortcuts are great. Even so, a person can only be expected to remember so many shortcuts and hit them accurately while giving a presentation over Zoom. [Sebastian] needed a good set of of shortcuts for OBS and decided to make a macro keyboard to help out. By the time he was finished, [Sebastian] had macro’d all the things and built a beautiful and smart peripheral that anyone with a pulse would likely love to have gracing their desk.

The design started with OBS, but this slick little keyboard turned into a system-wide assistant. It assigns the eight keys dynamically based on the program that has focus, and even updates the icon to show changes like the microphone status.

This is done with a Python script on the PC that monitors the running programs and updates the macro keeb accordingly using a serial protocol that [Sebastian] wrote. Thanks to the flexibility of this design, [Sebastian] can even use it to control the office light over MQTT and make the CO2 monitor send a color-coded warning to the jog wheel when there’s trouble in the air.

This project is wide open with fabulous documentation, and [Sebastian] is eager to see what improvements and alternative enclosure materials people come up with. Be sure to check out the walk-through/build video after the break.

Inspired to make your own, but want to start smaller? There are plenty to admire around here.

Continue reading “Dynamic Macro Keyboard Controls All The Things” →

Using MIDI To Solve A Keyboard Shortcut Problem

February 16, 2021 by Donald Papp 4 Comments

[Pete] admits that his MIDI-based slide advance alert system is definitely a niche solution to a niche problem, but it is a wonderful example of using available tools to serve a specific need. The issue was this: [Pete] is involved in numerous presentations streamed over video, and needed a simple and effective way for the Presenter to notify the Producer (the one responsible for the video streaming and camera switching) to discreetly advance slides on cue.

To most of us, this is a simple problem to solve. Provide the presenter with a USB macro keyboard to trigger the keyboard shortcuts for slide advancement, and the job’s done. But that didn’t quite cut it for [Pete]. In their situation, the Producer is managing more than just the slides as they switch between cameras, watch the chat window, and manage the video streaming itself. Triggering slide advancement via keyboard shortcuts only works if the presentation software is in focus when the buttons are pressed, which isn’t guaranteed.

[Pete’s] solution was to make a small two-button device (one button for next slide, one for previous slide) that uses MIDI to communicate with a small custom application on the producer’s machine, and doesn’t care about application focus. Pressing the slide advance button plays a distinct tone into the producer’s headphones, plus the custom application displays “Forward”, “Back”, or “Waiting” in a window, depending on the state of the Presenter’s buttons. The design is available on Instructables for anyone wanting a closer look.

[Pete] reports that it works and it’s far more discreet than saying “next slide, please” twenty or more times per presentation. You may notice from the photo that LEGO bricks play a prominent part in the device, and if you’d like to see more of that sort of thing, make sure to check out these other brick-mountable PCB designs.

FreeTouchDeck Upgrades Its Hardware And Its Name: ESP32 Touchdown

February 14, 2021 by Matthew Carlson 23 Comments

With many folks continuing to work from home for far longer than they ever thought, it’s no surprise that we’re seeing the rise of small DIY devices to make that video call or virtual presentation a little easier. [Dustin Watts] was interested in the functionality of the Elgato Stream Deck — a macro keyboard where each key is its own screen. But that kind of fancy hardware comes with a formidable price tag. So he built his own, and made it open source!

His first iteration — FreeTouchDeck — was built using commonly available modules but has since evolved into the ESP32 Touchdown which does it all with a single PCB. It’s a highly-customizable touchscreen macro keyboard which provide easy access shortcuts and macros for quick actions. Need a quick mute button, want to switch camera views on OBS, or maybe you want smarter shortcut keys for your CAD of choice. This will can get you there.

There a few key differences from the first version (FreeTouchDeck). The ESP32 dev board was ditched for a tidy PCB the directly integrates the module. This one has a capacitive touch controller (FT6236) rather than a resistive one as the capacitive screens deliver a far nicer user experience. A built-in battery and charger circuit (which the FreeTouchDesk didn’t have) allows for the extra bit of flexibility to stream from anywhere (within wireless range of course). Multiple case designs are available in STL form that allows it to be placed on a wall or desk with ease.

Datasheets, gerbers, kicad files, BOMs, and example firmware is provided on GitHub. The software is easily configurable so it can be set up to do any sort of macro, key combination, or action. This isn’t just limited to emulating a Bluetooth keyboard as there are examples showing how to connect to Home Assistant. All in all, this is a wonderful example of continued iteration on a project.

Thanks [Timothy Gregory] for sending this one in!

This Joy-Con Grip Steers Its Way To Sweaty Victory

February 8, 2021 by Kerry Scharfglass No comments

Here at Hackaday we’re always exited to see hacks that recycle our favorite childhood consoles into something new and interesting. In that context, it’s not so uncommon to see mods which combine new and unusual control methods with old devices in ways that their manufacturers never intended. What [Mike Choi] has built with the Labo Fit Adventure Kit is the rare hack that combines radically new control schemes with a modern console: without actually modifying any hardware.

In short, the Labo Fit Adventure Kit lets the player play Mario Kart on the Nintendo Switch by riding a stationary exercise bike, steering with a wheel, and squeezing that wheel to use items. The Fit Kit combines the theme of Labo, Nintendo’s excellent cardboard building kit for the Nintendo Switch with the existing Ring-Con accessory for the unrelated Nintendo game Ring Fit Adventure plus a collection of custom hardware to tie it all together. That hardware senses cadence on the stationary bike, watches for the user to squeeze the handheld wheel controller, and translates those inputs to button presses on the controller to play the game.

The most fascinating element of this project is the TAPBO module which adapts the Joy-Con controller to remote input. The module includes electronics, actuators, and a clever mechanical design to allow it to be mounted to the Ring-Con in place of an unmodified Joy-Con. Electrically the components will be familiar to regular Hackaday readers; there is a breakout board for a Teensy which also holds an XBee module to receive inputs remotely and drive a pair of servos. The entire module is described in detail starting at 4:42 in the video.

Mechanically the TAPBO relies on a pair of cam-actuated arms which translate rotational servo motion into linear action to press shoulder or face buttons. The module directly measures flex of the Ring-Con with an added flexible resistor and receives cadence information from another module embedded in the stationary bike via Zigbee. When these inputs exceed set thresholds they drive the servos to press the appropriate controller buttons to accelerate or use an item.

We’ve focused pretty heavily on the technical aspects of this project, but this significantly undersells the level of polish and easy to understand documentation [Mike] has produced. It includes a TAPBO Amiibo in customized packaging, and more. Check out the full video to get the complete scope of this project.

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Master Video Call Control Panel Is Made Of PCBs

January 30, 2021 by Kristina Panos 6 Comments

[memestra] is a teacher whose life has become a series of videoconferences over the last year or so. With all the classes and meetings, they spend the whole day switching between either Zoom, Teams, or Meet. If anyone needs a single piece of hardware to control them all, it’s [memestra]. Well, and every other teacher out there.

The hardware — an Arduino Pro Micro and some buttons — should come as no surprise, except for maybe [memstra]’s use of a resistor network for the LEDs. Still, there’s a lot to like about this little box, starting with the enclosure. That’s not milled or laser-cut metal — each side is a PCB, and they’re all soldered together into a box.

We especially like the top panel, which fits down over the PCB that all the components are soldered to. Each of the non-volume buttons has multiple functions that are accessed by pressing, long pressing, or double pressing. But even the volume buttons do double duty: press them together to mute and un-mute. If [memestra] ever forgets which button does what and how, there’s a handy reference table silkscreened on the bottom panel.

In true teacher fashion, [memestra] has written comprehensive instructions for anyone looking to build a similar device. The heavily-commented code should make it a cinch to drop in keyboard shortcuts for Discord or anything else you might be using, though it’s worth noting that this box is optimized for the desktop apps and not the browser-based versions.

Just looking for a fun way to end video calls? Pull chains are pretty fun.