LCD Related Basics

1, what is LCD?

(1) LCD (Liquid Crystal Display) is commonly known as liquid crystal. Liquid crystal is a material, liquid crystal This material has a feature: can be driven under the electric signal of the liquid crystal molecules to rotate, the rotation will affect the light transmittance,

So we can use the whole LCD panel behind the white Light (called backlight), can be used by different electrical signals to allow the selection of liquid crystal molecules, at this time in front of the LCD panel to see a variety of different

Color, this is the LCD display.

(2) Active and passive luminescence: some displays (such as LED displays, CRT monitors) themselves will be glowing called active light, some (LCD) itself will not glow only light, need to help backlight

To appear to be glowing, called passive glow.

(3) LCD display principle and characteristics (liquid crystal molecule light + backlight): White is actually composed of a variety of different colors, so the white lights can produce a variety of different colors of light after transmission. And the back of the LCD

The light is white.

(4) LCD application field: TV, computer display, mobile phone display, industrial display, etc.

(5) The history of LCD (TN/STN/TFT)

TN earliest. The disadvantage is that the response is not good enough, there is the phenomenon of trailing.

STN is an upgraded version of TN. Effectively solve the trailing phenomenon, display clearer.

The biggest feature of TFT is ultra-thin. TFT technology developed a lot of newer technology.

2, other mainstream display equipment (LED, CRT, Plasma, OLED)

(1) CRT: Cathode camera tube display. The old big-butt TV is the CRT display, which used to be one of the most widely used displays, but it's basically not in use.

(2) Plasma display: Using the high-speed development of plasma plane screen technology in recent years a new generation of display equipment, but failed to become mainstream.

(3) OLED: Organic light emitting diode also known as electromechanical laser display (Organic light-emitting diode,oled), OLED display technology with self-luminous characteristics, using a very thin organic material coating

And glass substrates, can be made lighter and thinner, visible angle is larger, and can significantly save energy. It is not mainstream yet, but it has market potential and is likely to replace LCD in the future.

(4) LED: Mainly used in outdoor large screen

(5) LCD: currently a mainstream display

3, LCD interface technology

(1) In essence, the SOC pin level standard is the TTL level, the 0V represents the logic, the logic 0, which is the TTL level. (about these level standards, interface standards There's time I'll be in the other posts

I don't know much about these things.

(2) So for the LCD controller built into the SOC, his interface output is also TTL level, we call this interface TTL interface (also known as the RGB interface). If the LCD hardware interface is also the TTL interface, then

can be directly connected (usually through the soft cable connection), but a very realistic reason, TTL level has a large defect, for example: can not be transmitted too far, anti-jamming ability is poor. So a lot of LCD hardware interface is not

TTL interface, but the use of other interfaces, so in order to be able to match, our motherboard side of the interface should be and LCD hardware interface must correspond, so we should put the LCD controller output TTL interface

Signal through the IC chip to convert it into the LCD hardware interface corresponding to the interface signal, so that they successfully complete the communication.

(3) TFT-LCD Interface: TTL (RGB), LVDS, EDP, MIPI (these interfaces are also connected through the soft line, for mobile phones, tablets, etc.)

(4) TTL (RGB) interface

The LCD controller TTL output interface generally contains RGB data signal, clock signal and control signal of the three categories of signals. As shown in the following:

(5) LVDS interface

(5.1) The LVDS, or low Voltage differential signaling, is an interface for differential signaling technology. Low noise and low power dissipation are achieved thanks to low-voltage and low-current drive modes.

(5.2) LVDS Interface Circuit composition

In a liquid crystal display, the LVDS interface circuit consists of two parts, the LVDS output interface circuit (LVDS transmitter) on the motherboard side and the LVDS input interface circuit (LVDS receiver) on the LCD panel side. LVDS

The transmitter converts the TTL signal to an LVDS signal, and then transmits the signal to the LVDS decoder IC at the LVDS receiver side of the LCD panel via a flexible cable (line) between the drive plate and the LCD panel, and the LVDS connection

The receiver then converts the serial signal to the parallel signal of the TTL level, sending it to the LCD screen timing control and the row and column driving circuit. In fact, the TFT only recognizes TTL (RGB) signals.

The LVDS signal consists of a data differential and clock differential signal, as shown in:

The display is a single channel 8-bit data mode: There are 5 sets of differential lines, 4 signal lines, a set of clock lines. Are y0m, y0p, y1m, y1p, y2m, y2p, Clkout_m, clkout_p, respectively.

(6) EDP interface

EDP (Embedded DisplayPort) is a full-digital interface based on the display port architecture and protocols that can be used to pass high-resolution signals with simple connectors and fewer pins, with a higher transfer rate than LVDS.

As can be seen from the above: EDP interface signal by main Link, Auxch, HPD

(7) Mipi interface

Reference: http://blog.csdn.net/xubin341719/article/details/9125799

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LCD Related Basics