POPULAR INTERFACES TO IMAGE TRANSFER 

In recent years, LCD-TFT has generally adopted RGB and LVDS interfaces. Use the RGB interface for resolutions lower than 1280x800 pixels, and use the LVDS interface for resolutions higher than 320x240 pixels. Most of today's advanced microprocessors and microcontrollers have been upgraded to RGB or LVDS drivers, thus simplifying the implementation of LCD-TFT in terminal equipment.

RGB
The RGB interface is based on parallel data transmission through at least a few lines. Each line can transmit 1 bit of information, which is used to determine the RGB color intensity of the pixel. Depending on the type of RGB interface, a certain number of wires are required.

In the RGB interface, there are five types of signals:

VSYNC (Vertical synchronization is used to synchronize the data of the display pixel column);
HSYNC (Used to display the horizontal synchronization of pixel row data);
D0...DXX (each bit of information has a separate line);
DCLK (dot clock used to synchronize data);
DE (Data Enable-a mode used to confirm the accuracy of data transmission).
RGB interface values performance very much-its bandwidth is estimated to be even as high as 1.2 Gbit/s. However, to achieve these values, you need to use more wires in a configuration, which leads to higher electromagnetic interference emissions.

LVDS (low voltage differential signaling)
The LVDS interface used for image transmission requires four differential pairs-one for clock signal transmission and three for data transmission. It provides simplex and serial communication-each bit of data is continuously transmitted in one direction. The information is transmitted as the difference between the voltages on a pair of wires; then, it is compared at the receiver. In the LVDS interface, there are three modes of data synchronization: VSYNC (vertical synchronization), HSYNC (horizontal signalization) and DE (data enable).

The LVDS interface is also valued because of its performance. Usually, it is used in a point-to-point topology (with one transmitter and one receiver), and it provides up to 3.125 Gb/s bandwidth even within a few meters of distance between devices. And LVDS is relatively resistant to electromagnetic interference.

eDP (embedded display port)
The eDP interface was created by VESA (Video Electronics Standards Association) and has been developed for implementation in consumer electronic devices with embedded LCD-TFT. In the computer industry-in this area, we can notice that the eDP interface replaces the LVDS interface. However, the eDP interface is not commonly used in microprocessors or microcontrollers.

eDP technology borrows from DP, so the Display Port standard is based on differential signal pairs – one pair is used for clock signal transmission and at least one pair is used for data transmission; in addition to them, there are half-duplex AUX channels for configuring LCD-TFT Controller. We can say that the structure of the eDP interface is similar to the structure of the LVDS interface, in which the transmitted information is "packed" in different ways-in the eDP interface, it is a serial transmission of information compressed packets. In the eDP interface, there are three modes of data synchronization: VSYNC (Vertical Synchronization), HSYNC (Horizontal Signalization) and DE (Data Enable).

It is recommended to use the eDP interface for LCD-TFT with a resolution of up to 3840x2160 px, 60 FPS and 24 bpp. However, the best image quality is obtained at 1920x1080 resolution and 240 FPS and 24 bpp or 2650x1600 resolution and 60 FPS and 48 bpp. Its bandwidth can even reach 1.62 Gb/s. It is also worth noting that the eDP interface is relatively resistant to electromagnetic interference.

MIPI DSI-MIPI (Mobile Industry Processor Interface) Consortium’s DSI (Display Serial Interface)
DSI technology is developed by the MIPI Alliance. It is mainly used in portable devices such as smart phones, tablets and laptops, but can also be used in, for example, mobile measurement devices.

The MIPI DSI interface is also based on differential signal pairs. It provides two-way full-duplex communication. Two data synchronization modes are used to transmit information as compressed packets:

Low power consumption (LP)-In this mode, the clock signal is suppressed; the information of the clock signal is transmitted through a pair of data transmission lines; it is mainly used to transmit information/initialization to the display;
High Speed (HS)-In this mode, the clock signal is transmitted by a single pair of wires; it is only used to transmit images.
The communication protocol consists of two sets of commands: Display Command Set (DCS)-a set of general commands defined by the DSI standard, for example, sleep, enable or reverse display and Manufacturer Command Service (MCS)-a set of display manufacturers defined Commands; they may involve, for example, entering data into the non-volatile memory of the screen driver.

The key assets of MIPI DSI are high efficiency, low power consumption and resistance to electromagnetic interference.

Vx1 (V-by-1 / V-by-One)
With the market launch of FHD (1920x1080) and UHD (3840x2160) displays, the Vx1 interface developed by Thin Electronics has entered the market, which is more resistant to electromagnetic interference than the LVDS interface.

The image transmission standard of Vx1 is similar to the LVDS image transmission standard, but Vx1 guarantees low production costs with high-speed data transmission. For each pair of differential lines (even if the distance is 10m!), it can even reach 840 Mb/s. The Vx1 interface is an asynchronous solution-the clock signal is transmitted through the data line, so there is no clock signal line. In fact, the total number of wire pairs is reduced. Let's compare: To start a Cinema-FHD (2560x1080) resolution screen with 30-bit color depth and 120 Hz refresh rate, you need to use 24 pairs of wires in the LVDS interface or... use 4 pairs of wires in the Vx1 interface.