TECHNOLOGY IN SYSTEMS
User Interface Design for Small Devices
Unlocking the Potential of a Multi-Touch Experience
Creating an effective multi-touch user interface requires a combination of technology and art. The foundation must be reliable hardware with adequate graphics and processing performance. This must support a UI design that understands the user’s needs and behavior.
MARK HAMBLIN, TOUCH REVOLUTION
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Today’s smartphones and tablets have awakened the world to the capabilities and ease of use of multi-touch systems. Innovative OEMs, ODMs and systems integrators are designing multi-touch capabilities into products as far ranging as retail point-of-sale systems, industrial control equipment, seatback entertainment systems and white goods. The research firm Display Search forecasts the total touch screen module market will grow to $9 billion annually by 2015, from $3.6 billion in 2008, a CAGR (compounded annual growth rate) of 14%.
Drivers of the Multi-Touch Experience
While traditional keyboards and mice will have a place in certain applications, multi-touch will continue to proliferate into a wider range of products, replacing lower-tech interfaces such as buttons, dials and knobs. Five key factors are driving the expanded use of multi-touch interfaces.
A well-designed multi-touch interface simplifies the interaction with the device by providing features that are more intuitive. For example, any user of a smart device knows that if they spread their fingers apart on a screen, the image will zoom in. Multi-touch provides for more accessible interfaces and also enables continuous inclusion of new functions into a device. Therefore multi-touch helps “future proof” a device since software can be continuously upgraded.
A well-implemented multi-touch interface can be much simpler to use than a conventional mechanical or button-based interface. It can show the user only those controls that are relevant to a particular operation versus conventional controls that are always visible to the user. This characteristic also facilitates expanding the interface’s functionality since additional functions can remain hidden until they are needed (Figure 1).
Multi-touch graphic displays allow the design of user interfaces that are graphically intuitive to the user and show only those functions that are relevant for the particular stage of interaction. They also ease the addition of functionality and specialized applications that convey the appropriate user experience.
Designers can also implement multi-touch interfaces to offer a sequential guide to help users through a series of control steps, similar to a “set up wizard” on a PC. These features improve the user experience by making the device easier to understand.
For example, many of today’s kitchen appliances include a multi-touch interface that appears at first glance to have fewer features since the interface is clean and simple. In fact, these appliances offer many more features than the button and knob controlled products of just a few years ago.
As seen on today’s smart devices, multi-touch interface gestures, defined as two-dimensional figure motions, can further simplify an interface and provide an intuitive user experience that transcends the typical “button replacement” configuration of most simple multi-touch interfaces. Gestures allow a sense of control over interface elements that mirror physical elements, allowing for a concept known as “direct manipulation.” For example, swiping emulates the finger motion involved in turning the pages of a book.
Interactive multi-touch interfaces provide a significant benefit over conventional static interfaces since designers can configure them individually for each user, languages can be changed as required, options can be simplified for beginning users, and pop-up help menus can appear automatically. The device can even automatically make these reconfigurations upon sensing information about the user. Accessibility will become increasingly important as multi-touch interfaces move into more devices and face an increasingly diverse user base.
A reconfigurable multi-touch interface without hardware dependencies enables designers to modify and improve the interface over time, and even upgrade and change the functionality of the entire device. Designers can introduce new features to devices after the initial sale, fix bugs remotely by upgrading the software over a network connection, reconfigure the interface after actual field usage data is collected, and load new applications on the device through an online store or other provisioning system.
As device manufacturers continue to add more complex features and interfaces, the ability to future proof will become increasingly important, as already realized in automotive and GPS applications.
A multi-touch interface is really just a blank slate onto which the control of any application or function can be placed. This allows a multi-touch interface to be the common element through which various functions can converge into one device. In the past, the need for different physical interfaces such as buttons determined the need for products and applications to be separate. For example, in a business environment, a physical business card file or phone list on paper is often located beside a desktop phone. Neither of these two products provides an interface that a designer can merge with the other. If a gesture-based multi-touch interface were implemented on the desktop phone, integrating a GUI-based electronic contact direction, there is an obvious workflow improvement.
Deploying the Multi-Touch System
Critical to the successful deployment of a multi-touch system is selecting the optimal multi-touch technology, controller board, enclosure and HMI, such as OS, graphics and CPU power. These components are customizable to fit a wide range of conditions and user needs. Clearly, a multi-touch system used on a forklift in a distribution center, a system used to operate an MRI machine in a hospital, and a system integrated into an informational kiosk outside a convention center have enormously different requirements.
There are several multi-touch technologies available, each with benefits and deficiencies. The flexibility of industrial design, optical clarity, accuracy, response speed, need (or lack thereof) for a stylus are among the factors that will guide the choice as to which multi-touch technology is best for a given deployment.
Projected capacitive (P-cap) technology provides a high-quality, multi-touch experience and suits a wide range of applications, including both indoor and outdoor environments and ranging from retail POS to industrial settings. It stands up well to wide temperature swings and is highly reliable. P-cap provides high chemical resistance, high impact resistance, an infinite number of touches and features high-strength glass (Figure 2).
P-Cap technology allows touch displays to be mounted so they can sense behind a protective layer of glass and implement multi-touch user interfaces for handheld and mobile devices.
Typically, projected capacitive sensors are made up of three major components: the sensor glass, the cover glass and a flexible printed circuit (FPC) with controller. The sensor glass includes a series of electrodes that are configured into rows and columns. These electrodes are made of a transparent indium tin oxide (ITO) conductive coating. Each electrode is routed back with a metal trace to a connection point where the FPC can be bonded. The FPC generally contains the controller for the touch sensor.
The cover glass is optically bonded on top of the sensor glass, burying the electrodes within the stack of the lamination. The cover glass serves as a dielectric between the user’s touch and the electrodes of the sensor glass. It also doubles as a barrier layer, protecting the sensitive electrodes from the environment and any potential damage.
The controller continually scans and monitors the capacitance of the electrodes. When a finger touches the surface of the cover glass it pulls a small charge from the electrodes, and using complex algorithms, the controller can determine the exact location of the touch.
When selecting a CPU board, designers must think through how the system will be used both today and in the future. Specific features to focus on include responsiveness, speed, unambiguous and simultaneous touches, integration with the display and the calibration required. One significant advantage of P-cap technology is it does not require calibration.
An advanced, complex multi-touch experience will require a more powerful CPU board to provide the performance the user will expect from the touch experience. And, a product with a simple multi-touch experience today where the designer plans to add more functionality in the future, may require a CPU board as or more complex than the advanced system described above, depending on anticipated functionality down the road.
As with every other component of the multi-touch system, selecting the right enclosure is critical to maximize performance. Some enclosures must be made of materials that resist harsh chemicals, such as those used to sterilize hospital equipment. Others must be sealed to ensure they are waterproof.
P-cap technology allows for a wide range of enclosure possibilities. Designers can flush mount the module, for example, avoiding the need for a bezel. This capability provides several advantages, such as preventing dirt, cleaning chemicals and bacteria from entering the modules. This is especially important in sterile environments, such as in medical facilities.
Getting the human-machine interface (HMI) right starts with a powerful processor that enables smooth graphics and a user interface that is well conceived and written. A weak processor or poorly designed graphical user interface renders an otherwise well-designed multi-touch computer worthless. A few key elements to ensure a successful user interface include ensuring that the functions reflect the user’s knowledge and behavior and that choices are made clear for the user through well-organized menus that are at most two to three levels deep. These second and third levels should closely resemble the first in order to make the experience easy to understand. In addition, there should also be understandable visual feedback, such as progress indicators, so users know where they “are” in a multi-step process.
Multi-Touch Deployment Best Practices
OEMs, ODMs and integrators seeking the benefits of a multi-touch experience must then tackle how to do it. While today’s smart devices act as benchmarks for a multi-touch experience, those attempting to create a similarly intuitive, easy-to-use multi-touch interface quickly learn it is not as simple as buying a capacitive touch sensor and wiring it into an existing product. Incorporating multi-touch capabilities into a product involves hardware, software, integration, optimizations and testing. Understanding and applying ten best practices will help designers maximize the power (and ROI) of a multi-touch experience.
Think holistically: Rather than connect a multi-touch computer to an existing product, think about creating a new product that is designed to take maximum advantage of multi-touch capabilities. Factors to consider include end user demographics, the product’s industrial design, system hardware selection and supported features.
Select the right multi-touch technology: The “right” technology will do more than meet requirements for today. The designer must understand how the product might be used in two to three years and build in functionality that will certainly make increased demands on the system.
Utilize a touch-friendly operating system: Developing an attractive, intuitive, gesture-based multi-touch GUI is a difficult process. Utilizing an operating system, such as Google Android, Apple’s iOS and Windows 7, which (to varying degrees) are specifically designed for touch, makes the designer’s job significantly easier by pre-integrating many common multi-touch user interface elements, such as sliders, selection switches and gestures like “flick to scroll” and “swipe.”
Don’t skimp on integration testing: Allowing sufficient time for integration testing is critical. Among the issues that are common and require attention include the effects of RF-EMI on the multi-touch sensor and software driver optimizations on the LCD and touch controller. Other factors include cable routing, application performance affecting touch responsiveness and unwanted optical interaction between the LCD and the touch sensor as well as ESD. Designers often underestimate the amount of effort required to integrate the hardware and software components into a cohesive, field-ready product. This results in deployment delays, budget overruns and even cancelled projects.
Ensure adequate graphics and processing horsepower: A powerful multi-touch interface can consume a significant amount of processor cycles. It is important to understand where processing takes place—in the multi-touch screen controller’s CPU, the host CPU or the host GPU? Without adequate processing horsepower in the right places to run an advanced user interface effectively and without latency, designing the system is pointless.
Choose the best display: Selecting the optimal display to integrate into a multi-touch device can be especially difficult due to the numerous dependencies between the display and the touch sensor. Among the factors to consider are RF-EMI interference issues between the display and the touch sensor, matching the active area and viewing angles, minimizing optical losses and bonding/sealing the display and touch sensors properly.
Correctly integrate the sensor: Most multi-touch sensors are made of glass, which has many benefits, but can also have drawbacks. The touch sensor must be integrated correctly to prevent breakage in the event of mechanical stresses. Slight deflections of the sensor could also interfere with the sensing baseline. Dust or other contamination must be kept from interfering with viewing quality, and ESD prevented from damaging the sensor or system.
Focus on industrial as well as interface design: By definition, multi-touch devices are intended to be highly interactive with the user. High-quality ergonomics, usability and intuitiveness are critical. This is important for both the GUI design as well as the physical design. For example, if the device is portable, designers must consider how the user will hold it and ensure there is either adequate room for the user to grip the device without touching the screen or build in grip suppression.
Optimize the touch software: There are many software layers involved in translating the motion of a finger or fingers on the multi-touch screen into a responsive action on the LCD and in the application software. The firmware running on the multi-touch controller, the touch and display drivers running in the OS and the application software itself must all be tested and optimized for responsiveness. Any lags in this software stack will result in a sub-optimal user experience.
Create a great GUI: That a multi-touch interface should include a great GUI seems obvious, but many designers fail to devote adequate attention to this. The interface should be much more than just a series of virtual buttons. It should reflect how the designer anticipates the user will interact with the product and facilitate that interaction.
To maximize the effectiveness of multi-touch systems, designers must clearly identify specific objectives and performance characteristics for the system. In a retail POS system, “effectiveness” might be measured as the incremental revenue and product volume uplift the system generates; while in an industrial environment, effectiveness is more likely focused on improving worker productivity and reducing inventory errors.
Careful thought and planning to the interface will help ensure that designers maximize the investment in the system by providing a high-quality user experience. Being in touch with the user’s needs and the operator’s objectives for the user will help ensure an optimal multi-touch return on investment.
Resources are available for designers building multi-touch into their products for the first time, as well as for those experienced with multi-touch, but eager to incorporate the newest designs and feature sets.
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