BeagleBones And Teensies Become KVMs

[pmf], like most of us, I’m sure, spends most of his days on a computer. He also has a smartphone he keeps at his side, but over the years he’s grown accustomed to typing on a real keyboard. He came up with the idea of making a USB switch that would allow his keyboard to control either his computer or his phone, and hit upon a really neat way of doing it. He’s using a BeagleBone Black and a Teensy to switch his keyboard between his computer and his phone with just a press of a button.

This homebrew smart KVM uses a BeagleBone Black for most of the heavy lifting. A keyboard and mouse is connected to the USB host port of the BeagleBone, and the main computer is connected to the device port. The BeagleBone is set up to pass through the USB keyboard and mouse to the computer with the help of what Linux calls a ‘gadget’ driver. This required an update to the Linux 4.0 kernel.

With the BeagleBone capable of being a USB pass through device, the next challenge was sending keypresses to another USB device. For this, a Teensy 2.0 was connected to the UART of the BeagleBone. According to [pmf], this is one of the few examples of the Teensy serving as a composite USB device – sending both keyboard and mouse info.

There are a few neat features for [pmf]’s build: the keyboard and mouse don’t disconnect when switching, and thanks to a slight modification of the USB OTG adapter, this will also charge a phone as well as allow for the use of a keyboard. Because the BeagleBone Black has more than one UART this build can also switch keyboards and mice between more than two computers. For those of us who invest heavily in keyboards, it’s a godsend.

Teensy Adds S/PDIF to Library

With Arduino library support on an ARM Cortex M4 processor, it’s no surprise that we’re fans of the Teensy 3.1. And lately, [Paul Stoffregen] has been building out the Audio Library for this platform, making it even more appealing to the synth / audio geeks among us. And now, with just the addition of a highfalutin LED and some software, the Teensy can output digital audio over optical fiber.

S/PDIF, and more specifically optical TOSLINK, uses LED light sent down an optical fiber to encode audio data. The advantage of this over any voltage-level signals (like with regular wires) is that the source and destination devices aren’t electrically connected at all, which gets rid of the dreaded ground loop hum and any RF interference.

An S/PDIF audio data stream is a bit complex, but if you’re interested [Micah Scott] has a fantastic dissection of it up on her blog. Of course, you don’t have to know anything about any of that to simply use S/PDIF with the Teensy Audio Library.

We love open source hardware and software because of the collaborations that make ultra-rapid development of niche stuff like this possible. You can follow along with the development of the Teensy’s S/PDIF capabilities on the PJRC forum. Contributor [Frank B] modestly claims that “everything was already on the internet”, but that doesn’t make it any less cool that they got from zero to working library in a few weeks. (And note the clever use of a precomputed lookup table for speed.)

LED_TOSLINK2On the hardware side, [Paul] has posted up his adapter board for a cheap, but very professional looking, optical TOSLINK sender. But if you’re feeling ghetto, you can simply use a red LED pointed just right into the optical cable.

The end result? Lossless transmission of CD-quality audio from an Arduino-esque microcontroller, sent on a beam of light, for less than the cost of a latté.

Roswell Eat Your Heart Out

When [Ian Wood] accidentally broke the camera on his fancy-pants FPV quadrotor he was a little bit upset. But out of all things we break, we hack something new. [Ian] decided to strap on some RGB LEDs to the drone and turn it into a UFO to scare his neighbors!

Now we know what you’re thinking: RGB LEDs? That hardly constitutes a hack! You’re right — but [Ian] didn’t just simply strap some LEDs on and call it a day. Oh no. He’s using a Teensy micro-controller and the NazaCANDecoder to listen to the CAN bus for RC stick positions, flight mode, altitude, battery data, etc. This means the LEDs are actually responding to the way he flies the drone. And since there was a spare channel on his Futaba RX controller, he’s also got an animation mode that can be controlled from the ground to do whatever he wants. He also got rid of the standard indicator LEDs on the quad and wired them into his new setup. They’re all being controlled by a FastLED library on the Teensy. Check it out in the clip after the break.

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Improving Active Loads

[Texane]’s job requires testing a few boards under a set of loads, and although the lab at work has some professional tools for this it seemed like a great opportunity to try out the Re:load 2. It’s a nifty little active load that’s available can of course be improved with an injection of solder and silicon.

While the Re:load 2 is a nice, simple device that can turn up to 12 Watts directly into heat, it’s not programmable. The ability to create and save load profiles would be a handy feature to have, so [Texane] took a Teensy 3.1 microcontroller and installed a resistor divider in front of the Re:load’s amplifier. A simple script running on a computer allows [Texane] to set the amount of current dumped and automate ramps and timers.

There is a more fundamental problem with the Re:load; the lowest possible current that can be dumped into a heat sink is 90mA. [Texane] replace the amplifier with a zero-drift amp that brought that 90mA figure down to 7mA.

Of course the Re:load and Teensy 3.1 are sold in the Hackaday store, but if you’re looking for a ready-built solution for a computer-controlled active load you can always check out the Re:load Pro, a fancy-smanchy model that has an LCD. The Pro costs more, and [Texane] just told you how to get the same features with the less expensive model we’re selling, though…

Play Robotic Bongos using your Household Plants

[Kirk Kaiser] isn’t afraid to admit his latest project a bit strange, being a plant-controlled set of robotic bongos. We don’t find it odd at all.  This is the kind of thing we love to see. His project’s origins began a month ago after taking a class at NYC Resistor about creating music from robotic instruments. Inspired to make his own, [Kirk] repurposed a neighbor’s old wooden dish rack to serve as a mount for solenoids that, when triggered, strike a couple of plastic cowbells or bongo drums.

A Raspberry Pi was originally used to interface the solenoids with a computer or MIDI keyboard, but after frying it, he went with a Teensy LC instead and never looked back. Taking advantage of the Teensy’s MIDI features, [Kirk] programmed a specific note to trigger each solenoid. When he realized that the Teensy also had capacitive touch sensors, he decided to get his plants in on the fun in a MaKey MaKey kind of way. Each plant is connected to the Teensy’s touchRead pins by stranded wire; the other end is stripped, covered with copper tape, and placed into the soil. When a plant’s capacitance surpasses a threshold, the respective MIDI note – and solenoid – is triggered. [Kirk] quickly discovered that hard-coding threshold values was not the best idea. Looking for large changes was a better method, as the capacitance was dramatically affected when the plant’s soil dried up. As [Kirk] stood back and admired his work, he realized there was one thing missing – lights! He hooked up an Arduino with a DMX shield and some LEDs that light up whenever a plant is touched.

We do feel a disclaimer is at hand for anyone interested in using this botanical technique: thorny varieties are ill-advised, unless you want to play a prank and make a cactus the only way to turn the bongos off!

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An RGB Word Clock, Courtesy Of WS2812s

A word clock – a clock that tells the time with illuminated letters, and not numbers – has become standard DIY electronics fare; if you have a soldering iron, it’s just what you should build. For [Chris]’ word clock build, he decided to build an RGB word clock.

A lot has changed since the great wordclock tsunami a few years back. Back then, we didn’t have a whole lot of ARM dev boards, and everyone’s grandmother wasn’t using WS2812 RGB LED strips to outshine the sun. [Chris] is making the best of what’s available to him and using a Teensy 3.1, the incredible OctoWS2812 library and DMA to drive a few dozen LEDs tucked behind a laser cut stencil of words.

The result is blinding, but the circuit is simple – just a level shifter and a big enough power supply to drive the LEDs. The mechanical portion of the build is a little trickier, with light inevitably leaking out of the enclosure and a few sheets of paper working just enough to diffuse the light. Still, it’s a great project and a great way to revisit a classic project.

Strapping an Apple II to Your Body

Now that the Apple wristwatch is on its way, some people are clamoring with excitement and anticipation. Rather than wait around for the commercial product, Instructables user [Aleator777] decided to build his own wearable Apple watch. His is a bit different though. Rather than look sleek with all kinds of modern features, he decided to build a watch based on the 37-year-old Apple II.

The most obvious thing you’ll notice about this creation is the case. It really does look like something that would have been created in the 70’s or 80’s. The rectangular shape combined with the faded beige plastic case really sells the vintage electronic look. It’s only missing wood paneling. The case also includes the old rainbow-colored Apple logo and a huge (by today’s standards) control knob on the side. The case was designed on a computer and 3D printed. The .stl files are available in the Instructable.

This watch runs on a Teensy 3.1, so it’s a bit faster than its 1977 counterpart. The screen is a 1.8″ TFT LCD display that appears to only be using the color green. This gives the vintage monochromatic look and really sells the 70’s vibe. There is also a SOMO II sound module and speaker to allow audio feedback. The watch does tell time but unfortunately does not run BASIC. The project is open source though, so if you’re up to the challenge then by all means add some more functionality.

As silly as this project is, it really helps to show how far technology has come since the Apple II. In 1977 a wristwatch like this one would have been the stuff of science fiction. In 2015 a single person can build this at their kitchen table using parts ordered from the Internet and a 3D printer. We can’t wait to see what kinds of things people will be making in another 35 years.

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