8/10/2009

Color TFT-LCD in Your Application

Color TFT-LCD panels are now finding their way into many embedded applications, enhancing the user interface and adding value to many products such as white goods, security control panels, building automation and climate control, point-of-sale devices, portable medical equipment, and industrial automation control. Light to medium graphic animation with a touch-screen interface cover most needs of these applications. Renesas is offering the Direct Drive LCD solution which uses a simple, low-cost Flash MCU to drive the TFT-LCD and touch-screen, as well as running the remainder of the embedded application. The alternative is often to use a higher priced microprocessor system which runs at much higher frequency. But for the level of animation used in these applications, the Direct Drive MCU solution is most cost effective, consumes less power, and has a smaller footprint on the PCB.

Direct Drive, How Does it Work?

The 16-bit H8S and 32-bit H8SX MCU families have devices with an External DMA controller (ExDMA), allowing the MCU to connect directly to a color TFT-LCD panel, and also to an external RAM frame buffer. The MCU’s ExDMA controller becomes the TFT controller, and independently manages the movement of RGB pixel data from the frame buffer to the display panel, while the MCU timers (TPU) manage the synchronization and clocking of the pixel data.

This Direct Drive LCD solution frees the CPU from the periodic task of refreshing the TFT-LCD panel. In fact, the CPU is loaded only 5% internally while the display is refreshed at 60 frames per second externally under control of the ExDMA unit and timers.

How well does Direct Drive perform?

As you can see in the example above, the 16-bit H8S/2378 MCU running at 35 Mhz can perform medium-intensity graphic animation on a QVGA (320 x 240) display with 16 bit-per-pixel color depth, a 60 frame-per-second display refresh, and a 50 frame-per-second animation rate. Remarkably, only 30% of the CPU internal bus is used, and only 60% of the external bus bandwidth is used in this animation example. This means the 35 MHz MCU can easily run the embedded application in addition to driving this color display.

The 32-bit H8SX MCUs can support color TFT-LCD panels with even higher resolution, such as VGA (640 x 480). These MCUs operate up to 50Mhz, and have up to one MByte of on-chip Flash memory.

What’s available to help create your own Graphics Animation design?

Renesas offers a complete solution for implementing graphic animation, including a hardware demonstration kit with everything needed to quickly get you started on your own evaluation and development. Also available is a free Graphics Application Programming Interface (GAPI) providing you, for example, the capability to create simple graphic animation, buttons, slide bars, and to manipulate text. For more advanced graphic animation requirements, such as creating windows and widgets, or alpha-blending, Renesas is allied with 3rd party software providers offering advanced graphic libraries which readily run on H8S and H8SX MCUs.