Drive a Color TFT-LCD with a low-cost Flash MCU!

Directly Drive a TFT LCD Panel and have ample bandwidth to run the application!

RX DDLCD

Color TFT-LCD in Your Application

Stylish graphical user interfaces have become an integral feature of the modern day embedded applications adding value to products spread across various application segments like the Consumer, Industrial & FInance, Medical, Building Automation, Automotive and many more. This has led to a sharp increase in the adoption of the small/medium size color TFT displays replacing the traditional monochrome segment displays. 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, 32-bit H8SX and the latest 32-bit RX600 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.

lcd direct drive animation intensity

How well does Direct Drive perform?

As you can see in the example on the left, 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 and RX600 MCUs can support color TFT-LCD panels with even higher resolution, such as VGA (640 x 480). These MCUs operate up to 100 Mhz, 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.

Guide to LCD Direct Drive Solutions
  System Clock Flash SRAM Features LCD Panel
H8S/2456Z 35 MHz 256-512 KB 16-32 KB High Speed Serial Interfaces, Timers, USB Device QVGA(320 x 240) WQVGA(480x272) VGA(640x480)
H8SX/1668 50 MHz 384-1024KB 48 KB High Speed Serial Interfaces, Timers, USB Device WQVGA(480x272) VGA(640x480) WVGA(800x480)
RX600 100 MHz Up to 2 MB Up to 256 KB High Speed Serial Interfaces, Timers, Ethernet Controller, USB, CAN QVGA(320 x 240) WQVGA(480x272)

Disclaimer:

The Direct Drive LCD solution is highly configurable, and capable of producing many different timing configurations which drive the input signals of TFT-LCD panels from various panel manufacturers. The signal timing generated from the Direct Drive LCD solution depends on your choice of panel resolution, frame buffer memory, and desired panel refresh and animation rates. Although Renesas provides guidelines and examples for configuring the signal timing, Renesas is not responsible for meeting the AC timing specifications of your specific choice of TFT-LCD panel, and Renesas explicitly disclaims any liability for the failure to meet such specifications. Please contact your TFT-LCD panel manufacturer to ensure the Direct Drive LCD solution complies with the panel timing limitations.

You can also refer to statements available from TFT-LCD panel manufacturers regarding panel timing:

Hitachi Electronic Devices
Sharp Microelectronics America

Related Kit
Embedded Video - Click here to add the video image