Transmitting MIDI Signals With XBEE

What do you do when you want to rock out on your keytar without the constraints of cables and wires? You make your own wireless keytar of course! In order to get the job done, [kr1st0f] built a logic translator circuit. This allows him to transmit MIDI signals directly from a MIDI keyboard to a remote system using XBEE.

[kr1st0f] started with a MIDI keyboard that had the old style MIDI interface with a 5 pin DIN connector. Many new keyboards only have a USB interface, and that would have complicated things. The main circuit uses an optoisolator and a logic converter to get the job done. The MIDI signals are converted from the standard 5V logic to 3.3V in order to work with the XBEE.

The XBEE itself also needed to be configured in order for this circuit to work properly. MIDI signals operate at a rate of 31,250 bits per second. The XBEE, on the other hand, works by default at 9,600 bps. [kr1st0f] first had to reconfigure the XBEE to run at the MIDI bit rate. He did this by connecting to the XBEE over a Serial interface and using a series of AT commands. He also had to configure proper ID numbers into the XBEE modules. When all is said and done, his new transmitter circuit can transmit the MIDI signals wirelessly to a receiver circuit which is hooked up to a computer.

Hackaday Links: June 29, 2014

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Ever see a really cool build on YouTube with no build details at all? Frustrating, right? That’s us with the NES Keytar covering the Game of Thrones theme. He’s using a Raspi with the sound chip in the NES to do live chiptunes. Freakin’ awesome. There’s also the ST:TNG theme as well.

A few years ago the folks at Oculus had an idea – because of cellphones, small, high resolution displays are really cheap, so why not make VR goggles? At Google IO this week someone figured out everyone already has a cellphone, so just wrap it in some cardboard and call it a set of VR goggles. You can get a kit here, but the only difficult to source components are the lenses.

What happens when you put liquid nitrogen under a vacuum? Well, it should evaporate more, get colder, and freeze. Then it breaks up into solid nitrogen snow. No idea what you would do with this, but there ‘ya go. Oh, [NC], we’re going to need a writeup of that LN2 generator.

About a month ago, the House4Hack hackerspace in South Africa told us of their plans to bring a glider down from 20km above the Earth. They finally launched it, The CAA only allowed them to glide back from 6km (20,000 feet), but even from there the foam glider hit 230kph (124 knots). That’s a little impressive for a foam FPV platform, and we’re betting something with a larger wingspan would probably break a spar or something. Shout out to HABEX.

All the electronic dice projects we’ve seen have one thing in common: they’re not cubes. Thus uberdice. It’s six nine-pixel displays on the faces of a cube, powered by a battery, and controlled by an accelerometer. Yes, it is by far the most complicated die ever made, but it does look cool.

[Jeri Ellsworth] on making her c64 bass keytar

[Jeri Ellsworth] finally set aside some time to talk about the build process for her Commodore 64 bass keytar. We think what started by taking a band saw to the guitar body ended up as a fantastic new instrument.

When she was showing off the project at Maker Faire we really only got a cursory look at what it could do. Her most recent video covers all that went into pulling off the project. Once the bulk of the guitar body was gone she tore the guts out of a dead c64 in order to mate the case with the guitar neck. Always the craftsman, she altered the computer’s badge to preserve the iconic look, then went to work adding pickups to each string using piezo sensors. This was done with Maker Faire in mind because magnetic pickups would have been unreliable around all of the tesla coils one might find at the event. These were amplified and filtered before being processed via an FPGA which connects to the original c64 SID 6581 chip.

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