Mark Matamoros ITP Blog

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Fall 2020

Textile Interfaces

Final Project. November 2, 2020.


For my final project, I chose to create a Bluetooth MIDI controller for guitar straps. While other MIDI guitar attachments have been typically designed to sit on top of the instrument's body, a strap-fastened device allows the user to maintain the guitar's aesthetics and body's real estate. Though this particular design allows a guitarist to manipulate effects via analog sensors, the unit can be re-programmed for other MIDI control needs.


The unit's construction entailed the fastening of three analog sensors, a development board, and a bluetooth module to a stretchable, non-conductive fleece-like material. Furthermore, velcro was attached to the backside-ends of this large fabric piece for securing the work. Regarding the component attachments, hot glue, conductive thread, and non-conductive thread were utilized to connect the items.


All of three pressure-sensitive, analog sensors were designed in a nearly idential manner. Conductive fabric surrounded the inner velostat (resistor) to vary the incoming voltage. Thereafter, an Adafruit Flora (development board) grabbed the three incoming signals and converted them into useable MIDI values. Regarding the transmission of MIDI data, a FLORA Bluefruit LE (bluetooth) module was wirelessly connected to the computer for guitar effect processing. It must be noted that while the video demonstration contains a connected mini USB cable to the development board, Bluetooth was being utilized for the connection. This issue pertained to the monitoring of generated MIDI values and the handling of a (potential) faulty battery.


Regarding playability, the design requires the user to utilize the strumming hand to interact with the analog sensors. These particular pressure pads are rather sensitive; therefore, the user must finesse the controller to produce a wide range of MIDI values. And regarding these mapped values, conditional statements in conjunction with mathematical manipulation created an output range between 0 and 127.

The following pictures and video display and demonstrate my project. It must be noted that the sensors and programming are set to manipulate Native Instrument's Guitar Rig 5, a plug-in for guitar processing. Furthermore, these sensors are specifically manipulating a harmonizer, tremolo, and wah effect.



I am eager to recieve another JST-connecting battery to test my circuit, as the present one is not powering my unit. Furthermore, if my project proves to be functional in this particular setup, I will need to design a pouch to house this extra component. Additionally, the programming pertaining to the analog sensors appear to be too sensitive. I will need to reassess this area and manipulate the current script to remedy this situation.

Lastly, it must be noted that Adafruit's BluefruitLE nR51's "MIDI" example was heavily utilized throughout the programming process.