Welcome back for another Design Challenge Project Summary. For those of you who are new to my content, in this series I will pick a single project from the past week’s updates, and write a short summary of the project to date. Over the course of each challenge, I try to revisit each project at least once, and I am sure that some project summaries will get more than one update if they themselves are updated frequently. Some project creators like to keep their own project summary going, and this series is not meant to overshadow those post, but to highlight each project from an outsider's perspective.


The subject of this week’s installment is project PlectralEffects by Elliot Tanner (elliot.tanner). This project got off to a great start via a wonderful introduction post that laid out the project's goals, expectations, and a little background on its creator. Unfortunately it appears that shipping issues has caused a very long delay in the project getting off the ground, and even now, with two weeks left in the challenge, parts of the challenger kit have still not arrived.



In his first project update post, Elliot laid out the three key components to the project which included Real Time Digital Signal Processing utilizing the two available Programmable Real Time Unit Subsystems on the Beaglebone Black. The next key component to the project was listed as Input Control that featured up to two piezo transducers that would be used to determine the direction of a strum on a guitar string. The third and final key component to the project was listed as a custom PCB that would be used to clean up the input, output, and supporting electronics into a small and tidy package.



In his second post, Elliot described how he would create a circuit connection using a custom made guitar pick that would feature two conductive sides with an insulator separating them in the middle. This so-called sandwich would have a wire connected to each conductive side, and used to strum guitar strings which were connected to the circuit. When the metal faces make contact with the strings, the circuit is completed, and the signal is fed to an amplification circuit before being converted into MIDI data.



The circuit is fairly simple and contains two resistors, a diode, and a pair of transistors, One leg of the 3.3V side of the circuit is connected to a guitar string, while the other is connected to the custom made guitar pick. A 100k resistor is utilized here to prevent any current spikes from damaging the delicate circuitry of the Beaglebone Black. The two transistors in the circuit serve as an amplifier that raises the signals voltage to a level that can be used to trigger the Beaglebone Black.


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This brings us to today. After his last post, Elliot began the waiting game on the rest of his challenger kit to arrive. Unfortunately the Beaglebone Black has yet to arrive, and we have just two weeks left in the challenge. This has forced Elliot to continue forward with the project, but at a much more limited level. Elliot will be offloading the effect processing to a desktop PC that is running a DAW.



This will allow the LeoStick to act as a controller mechanism that will be used to pass HID compliant MIDI data to the DAW. The hardware for the project has also been greatly simplified, and now consist of the LeoStick, an alligator clip, and a guitar string. Good luck Elliot, and we can’t wait to see the finished project!

Update: May 4, 2016



In his second to last post, Elliot informed us that he has had some success using the steel strings on his guitar to feed in MIDI data to the DAW over a USB connection. This is great news, and since he’s utilizing class-compliant MIDI, the project should be able to work with Mac based devices as well. To top off this post he the showcased the project's progress with a five-minute long video that was really informative. In addition to the demonstration, Elliot also shared the Arduino-based source code that he is running on the LeoStick, which is something I have been curious about since he brought this nifty little device to my attention a few post ago.



After a couple of weeks of absence, Elliot posted the final update to Project PlectralEffects on April 10th. The project was capped off with a final, quite impressive, demonstration of the project in full working order. Elliot mentions that he did have a few hurdles to overcome, with one being a good understanding of how the MIDI Clock works. “The main challenge for me in implementation of the enveloped effects was gaining an understanding of MIDI Clock,” Elliot said. “The effect mode is varied between two states, depending on which side of the plectrum is used. Effects are tempo synced to the DAW and are in time with beats.  MIDI Clock generates a byte 0xF8 at exactly 24 pulses per quarter note.  The envelope effects are sinusoidal calculated at 1/24th of a 1/2 wave, or 0.130899 radians to keep in time with the MIDI Clock.”


Despite the Beaglebone BlackBeaglebone Black from the official challenger kit never arriving, Elliot managed to complete a fully functional musical instrument using the LeoStick, a custom made, double sided, metallic guitar pick, and some clever coding. While he did not make the top 3, I want to give a huge shoutout to Elliot for continuing to push this project forward despite several large obstacles. His drive to compete in this challenge has inspired myself, and I am sure that the same is true for many others. This was simply a wonderful project to follow, and I truly hope to see Elliot in future challenges! 


This final update wraps up my summary of project PlectralEffect, and subsequently my coverage of the Open Source Music Tech Design Challenge here at Element14. This project has served as inspiration to many, and I am sure that somewhere, someone is planning to make their own version! Tune in next week for another installment to the Design Challenge Project Summary Series here at Element14, and the beginning of my project summary coverage of the Make Life Accessible Design Challenge. Until then, remember to Hack The World, and Make Awesome!