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Home Appliances

User Interfaces Take On New Looks With Advanced Display Technology

Graham Wilson,
marketing manager for Renesas' H8S, H8SX and SuperH microcontroller product lines.

The latest technology from LCD suppliers has changed the 'look and feel' of consumer appliances. With aesthetics playing an ever-larger role in consumer choices, home-appliance manufacturers are using TFT LCD displays and Renesas microcontrollers to create user interfaces that are more pleasing, provide more features, and are more intuitive to operate. EDGE spoke to Graham Wilson, Marketing Manager of Renesas Technology America's System LSI Business Unit, to learn more about how and why this is being done.

EDGE: For nearly a century, home-appliance manufacturers used buttons and knobs to control their products. What is the reason for the changes we are seeing now?

Wilson: With more appliances offering advanced functions and capabilities, the user interface of these appliances is becoming quite complex, and a growing number of buttons, LEDs and multiple-segment displays are required to enable these features. At the same time, the cost of implementation is increasing. One way to solve this problem is to use a thin-film transistor (TFT) LCD panel, which allows multiple functions to be implemented in one window via a touchscreen panel.

Recently the price of TFT LCD panels has dropped, enabling home-appliance manufacturers to incorporate this technology into their products and put a lot more information on the display. For example, they can show appliance status, settings, and temperature readings using color, graphics, and even animation to give the panel a more pleasing appearance. With the touchscreen capability, button and slide controls can be put on the display, too.

Another important point is that with a TFT LCD display, appliance manufacturers can cost-effectively differentiate products within a product line by reusing in modified form the same graphic elements such as layout, button placement, operation, and animation?simply by changing the "skin" of the images. For example, they might change the back screen, the bit maps, or the colors on the display.

EDGE: So TFT LCD display screen technology is what makes this versatility possible?

Wilson: Yes, the TFT technology gives a pleasing appearance to a small display because the pixel resolution is higher than conventional LCD panels. The colors provide much greater contrast, too, and the display has a faster operating speed. That allows images to be animated without the ghosting that's sometimes seen on slower types of panel. For home appliances, TFT LCDs enable much improved user interfaces.

EDGE: Is it difficult for appliance manufacturers to add this display technology to their products?

Wilson: It can be. I would say that about one third of the design challenge involves the hardware?hooking up the TFT LCD panel, enabling it to run at low clock frequencies, and minimizing both power usage and electromagnetic interference (EMI). The other two thirds of the challenge involves the software ? being able to take a desired image and actually put it on the screen with animation and touchscreen functionality.?

Most of the manufacturers implementing these displays are not experts in LCD panel technology. Rather, they are world-class developers of home appliances. So when they move from a segment-type or LED display to a TFT LCD display, they may not have in-house expertise for implementing the graphical content. Increasingly, graphic designers or marketing teams are generating this content, not engineers. Thus, a technology gap must be bridged to get the images from the design tools onto the microcontroller (MCU) hardware.

EDGE: What are semiconductor suppliers doing to make things easier for appliance manufacturers?

Wilson: So far, most appliances that incorporate displays have been higher-end products. It's not uncommon, for example, to see premium refrigerators that have large LCD panels similar to computer screens. But these require high-cost MCUs to drive the displays. What's been missing is a high-performance TFT LCD solution for cost-sensitive applications. However, Renesas now has an easy solution with the MCUs in the H8S and H8SX MCU families. We provide devices that can drive the TFT LCD panel directly and perform all the algorithms required for system operation at a very reasonable cost.

For simpler applications such as a pushbutton user interface without animation, or for products in which power consumption and battery life are issues, our 16-bit H8S MCUs are recommended. For mid-range products with more sophisticated graphics and animation or more complex algorithms for tasks such as temperature sensing, we recommend the devices in the 32-bit H8SX line. Renesas provides an easy, code-compatible path from the MCUs in the H8S family to those in the H8SX family for manufacturers wanting to move up from a smaller QVGA display to a full-size VGA.

If manufacturers want the highest performance to fully exploit the power of a TFT LCD panel ? say, to add TV, DVD-playback or video-camera features ? the devices in our SuperH family are perfect for circuit upgrades. All of these microcomputer families share the same Renesas development environment and software support infrastructure.

EDGE: Are there particular aspects of Renesas' MCU technology that make this possible?

Wilson: Wilson: The microcontrollers in the our H8S and H8SX families use an advanced bus architecture to directly drive the LCD panel (see Figure 1). In most other MCUs, the bus is partitioned in such a way that when data moves over the main path, the CPU core has to either stop or participate in the processing, which requires more than 100 MIPS. Renesas MCUs separate the CPU core from the data path. Therefore, the LCD direct-drive operation occurs in parallel to the operations of the CPU core and main system bus. Almost no CPU overhead is needed to drive the LCD, and far fewer MIPS are required to do it. The system runs at a much lower clock frequency, which reduces power consumption and EMI, and makes the circuit board less complex.

Our low-end and medium-end products also offer support for onscreen animation?a feature usually available only in high-end controllers. As you know, animation is done by changing the frame content. Despite the fact that the LCD direct drive and CPU core buses in our MCUs run in parallel, we use an innovative bus system controller that allows arbitration between the two, giving the CPU access to the frame buffer. By allowing interleaving on idle periods, the embedded control system can make effective use of the available CPU processing power.

Just as importantly, Renesas is making it easier for customers to create software for implementing graphics. We've developed a software application interface (API) that removes the complexity of acquiring images and getting them onto the display. We say that this API is "LCD-centric," which means that the commands called are defined as bitmaps, text, alpha blending and LCD-panel configuration.

Our software API is free with Renesas MCUs and is included in our development kit (See Figure 2). We are also working with third-party providers such as Segger Microcontroller Systems to support graphics tools and libraries for generating 2D images and animation quickly and easily.

Figure 1: H8S family's advanced bus architecture.
By minimizing the processing load on the CPU, this bus architecture allows the MCU to devote more processing cycles to performing other system connection algorithms and functions.

Figure 2: LCD development kit.
Using this complete kit, design engineers can easily incorporate TFT LCD panels into the embedded control systems of home appliances.
EDGE: Can you give an example of how manufacturers are using these user-interface features to enhance their products?

Wilson: Let's consider a thermostat that controls a home's heating, ventilation and air-conditioning (HVAC) system. Most thermostats today have simple segment-type displays that show the existing and desired temperatures, perhaps with buttons to change the settings. Moving to a TFT LCD panel with touchscreen controls changes the look of the panel completely. Not only is the appearance more pleasing, but also many more controls are possible, along with more sophisticated operation. At the low end, an H8S microcontroller could drive a QVGA display with pushbutton controls, perhaps with animation showing the current airflow configuration and temperature trend information.

By moving up to a mid-range H8SX MCU, manufacturers readily could upgrade the HVAC system. They might add different sensors in various rooms, use a larger VGA panel showing the layout of the home, and provide touchscreen controls for changing the settings in each room for different times of day. They could also use animated graphics with zoom capability to show the temperature, airflow, and other sensor status from room to room. Such features add convenience, allow better control of system operation, and produce a HVAC controller that has the appearance of a much more powerful and prestigious product.

EDGE: Can you describe some of the most important user-interface features we'll be seeing in the future?

Wilson: First, I must emphasize that the key drivers of this market are now and will continue to be low cost and ease of use. Nevertheless, across the spectrum of home-appliance products, we're finding displays that present images that are more sophisticated. The picture may be of the same pushbutton interface, but now the button doesn't just disappear when it's pushed ? instead it dissolves, a delightful experience. That requires more complex coding, and it's one reason why we've added the graphic software to our products to do alpha blending and transparency.

Also, the industry also is moving to single-chip solutions that support features such as touchscreen functionality. Such devices are among the many in the extensive Renesas microcomputer portfolio (see Figure 3). Our MCUs have direct connectivity to the analog touchscreen interface for integrated operation in low and mid-range products. In mid-range home appliances, we see more requirements for the CPU core to support such things as MP3 or JPEG decoding. In such cases, customers can put the processing capabilities of our high-performance H8SX MCUs to good use. Those chips can handle complex tone playback and image display while also driving the LCD panel, for example.

Other novel and useful user interface features are certain to be invented. Therefore, perhaps the most important advantage we offer to our customers is the unique architecture of the Renesas H8S and H8SX families. It lets home appliance manufacturers create system designs that can support improved display capabilities without incurring big increases in MCU complexity and cost.

Figure 3: MCU product roadmap.
Renesas offers many different microcomputers, covering a vast range of performance, feature, and cost requirements.
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