TetherPad

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.

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.

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.

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.

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.

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

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.

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.

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.

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

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.

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.