TetherPad

Jerez Bain, Sanmeet Chahil, Johan Seaton

Prototype Description

TetherPad is a musical interface powered by Arduino that offers an interactive sound-shaping experience using Firmata, Ableton Live, Max (Max for Live), and for this prototype, a granular synthesis engine. We envisioned the idea of creating an affordable, low-cost yet sturdy DIY pad controller to be used as an interface for live audio performance and improvisational experimentation. The TetherPad is powered by the capabilities of the Firmata library for Arduino, allowing the hardware to interface with Max for Live inside Ableton Live through the M4L Connection Kit. Ableton Live then is able to read the TetherPad’s five pressure sensitive textiles as analog input values to control mappable software parameters through touch. In our prototype, we explored the TetherPad’s response with SoundGuru’s The Mangle, a real-time granular resynthesis tool. Controlling grain rate, sample position, amplitude, and pitch of an audio sample, the TetherPad’s interface is ideal for dynamic timbral control, particularly with granular, spectral, and physical modelling synthesis techniques.

Circuit Layout

The Arduino is hooked up to a breadboard using the ground and power (5v) pins, and each individual pressure sensitive textile is hooked up to power through a 10k Ω resistor and ground. The resistive property of each individual textile is then sent to the arduino as an analog value.

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Code

With regard to code, the TetherPad only requires the standard Firmata library. You can view the exact code used to interface the Arduino here.

*initial tests paired with the 8-Pad sensor had us attempting to integrate the initialising code of the sensor with Firmata, though an issue of conflicting firmware made us rethink the use of the sensor, so we instead made all inputs analog.

Supporting Visuals

Top View dsc07646

 

Process Journal

Ideation.

When we collaboratively began brainstorming ideas for the prototype, we all came to a general consensus of wanting to create a sound-controlling interface. In this case, the ideal textile for our prototype was the pressure sensitive textile, as it generally gave consistent readings and was easily adaptable with paired with other conductive materials. Johan had extensive knowledge with interfacing Arduino with Ableton Live, so we decided that Live would be the brain of software side of our prototype.

Testing.

First, we began with wiring up a voltage divider circuit and the pressure sensitive textile as an input method. Then, we connected the Arduino to Live and began troubleshooting by calibrating the sensor to communicate effectively and activate sound. Once we got it to work correctly, we were planning on including the 8-pad capacitive touch sensor as well in order for the TetherPad to create more sound effects.

8-pad and sensor

Quickly we had realised that including the Firmata code and the 8-pad touch capacitive sensor in one file wasn’t working as well as we expected it to, so we went with only the pressure sensitive textiles.

Layout.

With regard to the physical layout, an early idea was to make the TetherPad’s build in installation form, using the 8-faceted pillar in the room as a surface. We realised that the pillars had quite the surface area and the amount of material required would be extensive and housing the electronics would have proved challenging. We then brainstormed a potential rotating surface as the body of the device, like a lazy-Susan or turntable, but a continuously rotating surface would have introduced some logistical issues that would have distracted the core idea. We eventually landed on the most simple and to the point rectangular planar housing for the TetherPad, the box being ideal for clean wiring inside and the the surface area large enough to facilitate more than one player. The element of play was crucial to informing the design choices from the beginning.

Building.

The two things we had to sort out when building the TetherPad were the equal cutting of the pressure sensitive textile, and a few minor modifications to the box. We began with measuring the height and the width of the TetherPad’s housing, and decided to go with a planar format of placing the pressure sensitive textiles.

Measuring TetherPad

As we only had 5 usable analog input pins on the Arduino, we measured and cut the width of each textile precisely.Measuring Textiles

Once we had cut the pressure sensitive textiles, we had to come up with a minimal way of wiring up each individual textile to power and their respective analog input pins. We had come to the idea of using nails to fixate the position of the pressure sensitive textiles and also connect the electrical current required to use each sensor.

Testing Nails

Next, we had to think of the ideal layout of the pressure sensitive textile, whether it be folded once or twice to fill the height of the surface area. After testing the signal when folding the textile once and twice, we decided that 1 fold was more ideal as two folds resulted in the unwanted upward flexing of the material.

HAMMERTIME!

We had hammered in each individual textile, then moved on to soldering the wires to the nails and securing the breadboard inside of the container.

Breadboarding

We successfully soldered each wire to its respective nail, then wired it to its ideal position on the breadboard.

Soldering

After connecting the wires to the breadboard, we decided on placing the Arduino inside of the box and letting a singular wire connect to the device controlling the TetherPad.

Wire!

We had cut a small hole in the box to access the USB port on the Arduino wire, and had successfully finished building the TetherPad.

Final Troubleshooting.

When we went ahead and tested the TetherPad, we realised that the pressure sensitive textiles were folding in on each other, allowing the signal of one textile pass onto the other, making for unwanted triggering of sound. In order to fix this issue, we had to separate each pressure sensitive textile to a greater extent than our initial tests lead us to believe. Using electrical tape and cutting the excess material of the sides of each textile, we were able to restore more consistent and reproducible readings across all sensor pads. In order to further boost the signal, we had included the usage of aluminium foil to allow for more conductivity between each pressure sensitive textile’s conducting nails.

Project Context

The TetherPad is a musical control surface that is neither cuts corners in design, nor aims to be a replacement of more sophisticated continuous controllers such as the Roli Seaboard or Haken Continuum (HakenAudio). The primary strength of the TetherPad is its limitations; being able to quickly map parameters to 5 pads allows user to experiment quickly with control mapping, bypassing the often tedious and all too familiar process of mapping every element of expression control that is inherent with more sophisticated controllers. The more sophisticated the controller, the more that needs to be mapped manually. On the flipside, no touch controllers in the low price market offer the particular type of control that the TetherPad excels at. The Roli Seaboard Mini carries the same time consuming mapping burden as its bigger counterpart, which ends up promoting the use of presets (“Seaboard GRAND Stage”), and Keith McMillan Instruments’ Qunexus with its flat plastic surface leaves much to be desired.

As for continuous or semi-continuous controllers, the closest cousin to the TetherPad is the classic Ribbon Controller (Jones), a device that converts the pressure and position of the player’s fingers into controlled voltage data. For playability, the larger surface area and ability to map multiple parameters across the surface makes the Tetherpad’s design advantageous for users who want flexibility in addition to a soft playing surface (McPherson).

The ultimate end goal of the TetherPad’s design is to prioritise playfulness over playability, not emulating existing expressive controllers and filling the gap in the controller market for an expressive tool that is both affordable and allows for rapid customisation. Many controllers on the market favour expression at the cost of customisation or customisation at the cost of expression. The blank-slate design of the TetherPad aims to approach this dilemma in a unique and rather direct way – instead of trying to do too many things at once, the aim of the device is to do one thing very well.

Bibliography

HakenAudio | Overview | Introduction, www.hakenaudio.com/Continuum/hakenaudioovervg.html.

Jones, Randy, et al. “A Force-Sensitive Surface for Intimate Control.” Madrona Labs, www.madronalabs.com/pdf/NIME09_k1_FINAL.pdf.

McPherson, Andrew. “Buttons, Handles, and Keys: Advances in Continuous-Control Keyboard Instruments.” MIT Press Journals, Queen Mary University of London, www.mitpressjournals.org/doi/pdf/10.1162/COMJ_a_00297.

“Seaboard GRAND Stage.” Next Generation Synthesizer | ROLI, roli.com/products/seaboard/grand-stage.
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