A touchscreen would not be much use without software (and hardware) to use it on. There’s two angles of attack that I’m playing with in my head. These are;

1. Software runs locally on the computer that is controlling the synths / ableton etc..
2. Software runs on another piece of hardware and utilizes MIDI over LAN (or something similar

There’s pro’s and con’s to both of these approaches. The first is easier to maintain and is more portable for the traveling DJ (unless you could really scale down option 2). However it has draw backs as the CPU power required to process the swishy graphics would detract from the power available for whatever application that it is controlling. Another thing is that it becomes a little more difficult to write portable code, by which I mean that it’s more work to write something for Windows / Mac / Linux.

The second approach is a little better in terms of systems segmentation and separation (which is beneficial, resources aren’t taken from the host that you want to contol). The downside is extra hardware and more work linking the host to the controller with MIDI over LAN.

Anyway.. whilst I think about this here’s some links to take a look at

http://monotouchlive.com/

“If you are looking for an alternative way to control Ableton Live, and you are not afraid of investing in a touch screen, look no further. Although other solutions, such as JazzMutant’s Lemur controller have been around for a while, the MonoTouchLive package is the first, flexible software application designed for mass produced tablet PC’s, rather than custom built machines.

The software package is a stand-alone software controller, with a six channel mixer, designed to allow control over Ableton Live with a touch screen, bringing compatibility to both Windows XP and Apple bootcamp machines. Using the touch screen interface and a normal display, the innovation is almost ready for its first release, and incorporates a crossfader, various start stop buttons, track navigation alongside effect parameters and eq in its simple yet powerful interface.”

.. more to come

Well, I think for the first informative post I should journey into the wonderful world of touchscreens.

Touchscreens come in many different shapes and sizes. Depending on the application used, some are better than others. For the purposes of this post, I’ll speak about 3 different types. These are;

• Resistive
• Capacitive
• Surface Wave Acoustics

Here’s some information stolen from wikipedia written by myself:

Resistive

A resistive touch screen panel is composed of several layers. The most important are two thin metallic electrically conductive and resistive layers separated by thin space. When some object touches this kind of touch panel, the layers are connected at certain point; the panel then electrically acts similar to two voltage dividers with connected outputs. This causes a change in the electrical current which is registered as a touch event and sent to the controller for processing. When measuring press force, it is useful to add resistor dependent on force in this model — between the dividers.

Capacitive

A capacitive touch screen panel is coated with a material, typically indium tin oxide that conducts a continuous electrical current across the sensor. The sensor therefore exhibits a precisely controlled field of stored electrons in both the horizontal and vertical axes - it achieves capacitance. The human body is also an electrical device which has stored electrons and therefore also exhibits capacitance. When the sensor’s ‘normal’ capacitance field (its reference state) is altered by another capacitance field, i.e., someone’s finger, electronic circuits located at each corner of the panel measure the resultant ‘distortion’ in the sine wave characteristics of the reference field and send the information about the event to the controller for mathematical processing. Capacitive sensors can either be touched with a bare finger or with a conductive device being held by a bare hand. Capacitive touch screens are not affected by outside elements and have high clarity.

Surface Wave Acoustics

Surface Acoustic Wave (SAW) technology uses ultrasonic waves that pass over the touch screen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. Surface wave touch screen panels can be damaged by outside elements. Contaminants on the surface can also interfere with the functionality of the touchscreen.

.. Well that’s all very well and good Joel, I hear you cry, but what does this mean in terms of creating a touchscreen interface for DJing / controlling sequencers & synths etc? It all boils down to application. When we control parameters on the screen, we generally move and drag. For this purpose, Surface Wave Acoustics is the best, as it maps the motion much better than the other two. Whilst they aren’t  bad, we need maximum accurate resolution to be able to make the most out of our kit.

There’s a fair few companies that sell SWA technology. One that comes to mind it ELO’s IntelliTouch screens. When purchasing a screen, I’ve become aware of this and have conducting my eBay bidding accordingly. With any luck I should have myself a nice 17″ TFT SWA bagged very shortly!

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