All You Need to Know About MCU and RGB Interface

 > All You Need to Know About MCU and RGB Interface

summary

MCU interface and RGB interface are widely used interfaces, among which MCU interface is the easiest to drive, but with the technical progress of tft screen and the problem of production cost, more and more tft display driver IC manufacturers have given up on WVGA, that is, 480×800 The production of MCU interface driver IC with above resolutions, but small lcd displays such as 1.14-inch, 1.77-inch and 2.4-inch are not affected. It is recommended that you pay attention to circumvention on new projects.

1.The Distinctions Between MCU and RGB Interfaces:

  1.1 What is MCU Interface?

  1.2 What is RGB interface?

2.Advantages and Applications of MCU and RGB Interfaces:

  2.1 MCU Interface Advantages

  2.2 Applications of MCU Interface

  2.3 MCU Interface Advantages

  2.4 Applications of RGB Interface

3.Converting Between MCU and RGB Interfaces

4.conclusion

With continuous advancements in LCD (Liquid Crystal Display) technology, we have witnessed significant improvements in color representation and resolution capabilities. From initially supporting only black and white, LCDs have evolved to display an astonishing 16.7 million colors. Additionally, resolution has seen substantial enhancements, progressing from basic formats like 16×2 and 16×4 to more complex formats like QVGA, HD, FHD, and even 4K. As resolution increases, the demand for transmitting large amounts of data has prompted the development of various LCD interfaces, each with specialized functions and classifications.

In the current industry, several widely used LCD interfaces include MCU interface, RGB interface, SPI interface, MIPI interface, LVDS interface, and eDP interface. The choice of interface depends on factors such as transmission rate, resolution, and noise immunity. RGB, MCU, and SPI interfaces are mainly employed in lower-resolution displays, while higher-definition displays usually utilize MIPI and eDP interfaces due to their high-speed transmission and excellent noise immunity. However, it is essential to note that these interfaces impose higher requirements on the driving processor, limiting their use in low-end microcontrollers, which predominantly rely on MCU and RGB interfaces.

The Distinctions Between MCU and RGB Interfaces:

What is MCU Interface?

The MCU interface, also known as the 8-bit or 16-bit parallel interface, comes in two variations: 8080 and 6800, with 8080 being the most prevalent. In this interface, the LCD driver IC is integrated with internal RAM. The host system sends commands and data to the driver IC, which processes the information and converts it into RGB data for each pixel on the display. Unlike the RGB interface, the MCU interface does not require continuous transmission of unchanged RGB data as it is stored in the driver IC’s internal RAM. This reduces the burden on the host system, making it suitable for applications with lower-resolution displays and simpler microcontrollers. The resolution supported by the MCU interface is limited by the size of the driver IC’s internal RAM, with the maximum display resolution typically being WVGA (480×800).

MCU interface driver IC structure

The biggest feature of the MCU interface is that the screen that needs to be displayed is stored in SRAM. As long as the screen is not updated, the CPU does not need to make any calculations

SRAM mapping

The MCU interface is divided into 8 bits, 9 -bit, 16 -bit, 18 -bit, 24 bits, and the most commonly used is 8 and 16 bits.

16bit MCU interface
8bit MCU interface
part of our MCU interface tft screen production

1.77-inch 128x160 QQVGA tft display

1.77-inch lcd panel, TN display mode, MCU interface, optimal viewing angle at 6 o'clock

2.4-inch 240x320 QVGA tft display

2.4-inch lcd panel, TN display mode, MCU interface, brightness and size can be customized

0.96-inch 80x160 LCD display

0.96-inch 80x160 tft display, MCU interface, IPS mode

0.96-inch lcd panel using MCU interface, 16.7M colors, using IPS display technology, all view direction

What is RGB interface?

The RGB interface is a common method for connecting TFT LCD panels to host systems. In this interface, each pixel on the display is controlled using individual red, green, and blue signals, enabling precise color representation. The host system needs to provide synchronization signals, such as HSYNC (Horizontal Sync) and VSYNC (Vertical Sync), along with other control signals like ENABLE, CS (Chip Select), RESET, and RS (Register Select), to drive the display. Additionally, the host must continuously transmit RGB data for each pixel to correctly render the content on the screen. The RGB interface can support higher resolutions and larger display sizes, but it places higher demands on the host system, requiring an LCD controller to manage data transmission effectively.

RGB interface driver IC structure

The display screen of the RGB interface is not SRAM, as long as the screen is displayed, it needs to be continuously synchronized signal and the data of the screen

RGB interface
part of our RGB interface tft screen production

4.3-inch 480x272 tft display

4.3-inch 480×272 lcd panel, RGB interface, driver IC is NV3047, Suitable for PAD, PMP, MP4, DVB-S, GPS products

7-inch-sunlight-readable-display

5-inch 800x480 tft display, sunlight readable display

5-inch 800×480 tft display, IPS mode, high brightness display, 1000cd/㎡, sunlight readable display.

3.95-inch-lcd-display

3.95-inch 480x480 tft display, rectangular display

3.95 -inch480x480 tft display, IPS mode, RGB interface, the brightness is 350cd/㎡, square display.

Advantages and Applications of MCU and RGB Interfaces:

MCU Interface Advantages

Displays using the MCU interface have lower requirements on the host system since data is directly written into the driver IC’s RAM. Consequently, when the displayed image remains static, the host does not need to send any commands. It’s worth noting that compared to the continuous need for RGB data and synchronization signals in the RGB interface, the MCU interface may have slightly lower power consumption. MCU displays offer relatively fast speeds and can support video playback and dynamic images.

Applications of MCU Interface

The MCU interface is still used in specific applications where lower display resolutions are sufficient, and cost-effectiveness is a priority. Although the MCU interface is not prevalent in high-end devices, it still holds significance in certain niche markets, such as simple wearables, basic digital signage, and small embedded systems. Due to its reduced data transmission requirements and compatibility with low-end microcontrollers, the MCU interface is favored in projects with limited budgets and processing capabilities.

RGB Interface Advantages

The RGB interface’s primary advantage is its ability to support larger display sizes, theoretically limited only by the transmission rate. In practical applications, displays supporting the RGB interface range from 2-inch screens to 10-inch displays, with the RGB interface capable of achieving relatively high resolutions, such as 1024×768. However, it requires an appropriate controller to drive the display effectively.

Applications of RGB Interface

The RGB interface continues to be widely used in the industry, especially for medium-to-high-resolution displays and larger screen sizes. It remains a popular choice across various applications, including smartphones, tablets, computer monitors, TVs, and other consumer electronics devices that demand high-quality and vibrant color representation. The RGB interface has continually evolved over the years, supporting higher resolutions, faster data transmission rates, and improved color accuracy.

As discussed, while the MCU interface requires the integration of RAM into the driver IC, resulting in higher costs for the accompanying driver IC, its usage has gradually decreased over time. Therefore, the number of manufacturers producing MCU interface driver ICs has diminished. Given the increasing popularity and advantages of alternative interfaces like RGB, we strongly recommend considering other interface options or exploring suitable interfaces based on project requirements and desired display functionalities.

Converting Between MCU and RGB Interfaces

The differences between the RGB and MCU interfaces, especially regarding the need for additional sync signals in RGB interfaces, make the conversion process relatively challenging. It is not recommended to attempt such conversions, as they would require additional TFT LCD driver chips or FPGA chips to perform the conversion, resulting in increased power consumption and costs.

A successful conversion would necessitate the determination of the existing display’s resolution and size to ensure a feasible conversion. The MCU interface is typically suitable for lower resolutions (maximum WVGA resolution), corresponding to weaker processing capabilities of the driving processor for such displays. Hence, selecting an appropriate resolution is crucial.

The key to the conversion lies in using FPGA or dedicated TFT LCD driver chips to implement signal conversion. Necessary data processing and control logic should be integrated into the MCU interface signals to enable effective communication with the LCD driver IC. Additionally, FPGA or TFT LCD driver chips have built-in RAM, allowing for data storage.

Once the hardware is completed, software debugging is required to initialize the driver IC and generate correct signals, such as pixel data, sync signals, and control commands, to achieve proper display performance and color accuracy.

part of our conversion board production
LVDS to LVDS converter board with added backlight control

LVDS to LVDS Converter Board

LVDS interface to LVDS interface adapter board, the maximum resolution is 2560×1440, and the boost and control circuit of the backlight are added

LVDS to RGB Converter Board

LVDS to RGB Converter Board

Adapter board for converting LVDS interface to RGB interface, the maximum resolution is 2560×1440, and the maximum refresh rate is 60Hz. It can be customized according to your requirements, adding touch screen and other functions

Specifications of HDMI, VGA to LVDS, TTL driver board

HDMI, VGA to LVDS, TTL driver board

The LCD driver board is mainly designed for TFT LCD screens. Input signal types: digital high-definition (HDMI), analog (RGB, VGA), PAL/NTSC composite video/VIDEO (default NC).

conclusion

The tft lcds we use now rely on the development of consumer electronics products. The birth and development of the MCU interface is due to the ability of the CPU and power-saving requirements at that time. With the development of the electronics industry, the resolution of the display screen is getting higher and higher, and the ability of the CPU is also getting higher. The best example is the 4.3-inch480x800 resolution display, the MCU interface is more than 50% more expensive than the RGB interface, obviously if you know these things when you start designing the product, you can avoid such things from happening.


In summary, the usage of the MCU interface has gradually decreased over time due to advances in display technology and higher resolution requirements. As a result, there are fewer and fewer manufacturers producing high-resolution MCU interface driver ICs today. Considering the popularity and advantages of other interfaces (especially RGB), we strongly recommend choosing a non-MCU interface display when choosing a higher resolution.

More Resources:

Display serial interface – Source: Wikipedia

Low voltage diffenertial signal – Source: Wikipedia

MIPI Display Serial Interface– Source: mipi.org

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