LCD screen interface types and their detailed descriptions

There are roughly seven types of LCD screen interfaces

SPI

This type of interface is less commonly used. It involves four wires: CS/, SDI, SLK, and SDO. Although the number of wires is small, its software control is complex. It is typically used on low-speed, small-sized monochrome screens.

I2C

I2C is also commonly used on low-speed, small-sized monochrome screens.

CPU

Commonly used in functional machines.

RGB

Commonly used on large screens.

LVDS

output interfaces are widely used in LCD displays of 17 inches and above.

MDDI

Introduced by Qualcomm, it will replace the SPI mode, becoming the high-speed serial interface in the mobile field.

MIPI

An organization formed by several major manufacturers.

Below is a detailed introduction to each interface

SPI (Serial Peripheral Interface)

SPI: A serial peripheral interface. It was first defined by Motorola on its MC68HCXX series processors. SPI enables serial communication between an MCU and various peripheral devices to exchange information. SPI has three registers: the SPCR (Support Register), the SPSR (Status Register), and the SPDR (Data Register). Peripheral devices mainly include network controllers, LCD drivers, FLASH RAM, A/D converters, and MCUs. The SPI interface is primarily used between FLASH, EEPROM, A/D converters, real-time clocks, and digital signal processors and decoders.

I2C Interface

I2C: The I2C bus is a two-wire serial bus developed by NXP (formerly PHILIPS). Its main advantages are simplicity and efficiency. The bus is used to connect microcontrollers and their peripheral devices. Another advantage of the I2C bus is its support for multiple masters; any device capable of transmitting and receiving can become a master. A master can control signal transmission and clock frequency. Of course, only one master can exist at any given time.

CPU Interface

CPU: Before the advent of smartphones, it was most commonly used in feature phones. With the rise of large-screen phones, the parallel port’s transmission speed became insufficient, especially for high-definition playback applications. This led to the development of MDDI and MIPI.

RGB Interface

RGB interface: A common mode used on large screens, with data bit transmission options of 6-bit, 16-bit, and 18-bit. Connections typically include: VSYNC, HSYNC, DOTCLKVLD, and ENABLE, followed by the data cable.

LVDS Interface

LVDS is a low-voltage differential signaling technology interface. Developed by National Semiconductor (NS) to overcome the drawbacks of TTL level transmission of wideband, high-bitrate data, such as high power consumption and significant EMI (electromagnetic interference), it is a digital video signal transmission method. Using an LVDS output interface effectively achieves low noise and low power consumption. In an LCD screen, the LVDS interface circuit consists of two parts: the LVDS output interface circuit (LVDS transmitter) on the driver board side and the LVDS input interface circuit (LVDS receiver) on the LCD panel side. The LVDS transmitter converts the 17L level parallel RGB data signals and control signals output from the driver board’s main control chip into low-voltage serial LVDS signals. These signals are then transmitted to the LVDS receiver on the LCD panel side via a flexible cable (ribbon cable) between the driver board and the LCD panel. The LVDS receiver then converts the serial signal back into a TTL level parallel signal, which is finally sent to the LCD screen’s timing control and row/column drive circuitry. The diagram below illustrates the composition of the LVDS interface circuit.

It should be noted that the LVDS transmitters on the driver board vary between different LCD monitors. Some LVDS transmitters may be one or two separate chips, while others may be integrated into the main control chip.

MDDI Interface

MDDI: Proposed by Qualcomm in 2004, this interface improves mobile phone reliability and reduces power consumption by reducing wiring. It replaced the SPI mode, becoming the high-speed serial interface in the mobile field. The wiring mainly consists of host_data, host_strobe, client_data, client_strobe, power, and GND wires.

MIPI Interface

MIPI: An organization formed by several major manufacturers, which launched a series of mobile standards, including MIPI DSI. Although MIPI has only been around for a short time, its adoption has been very rapid. Even the iPhone 4 and Meizu M9 use the MIPI interface (it’s estimated that most phones now, except for Qualcomm’s, use the MIPI interface). The MIPI interface has physical specifications; therefore, development boards and LCDs supporting DSI use MIPI-compliant cables. However, at present, LCDs with MIPI interfaces are basically unavailable for purchase. A small number of them are custom-developed online, and some use iPhone screen development boards. Panda Boards do not bring out the MIPI signal in the CPU, so they cannot be used. The Samsung S5PC100 development board also does not bring out the interface. The Samsung S5PV210 development board generally has the MIPI interface driver. Currently, only Omap code is available for our reference.

As a provider of LCD driver solutions for the industrial sector, LEEHON Technology Co., Ltd. has established in-depth partnerships with many leading global LCD panel manufacturers, including BOE, TIANMA, IVO, AUO, Innolux, and Kyocera, and professionally supplies multi-brand, full-series industrial-grade LCD displays and customized solutions.