LCD screen interface type

LCD screen interface type

The LCD screen has RGB TTL, LVDS, MIPI DSI interfaces. These interfaces are different from the type (type) of the signal and the content of the signal.

The signal type of RGB TTL interface is TTL level, and the content of the signal is RGB666 or RGB888, as well as line and field synchronization and clock;

LVDS interface signal type is LVDS signal (low voltage differential pair), the content of the signal is RGB data, line and field synchronization and clock;

The MIPI DSI interface signal type is LVDS signal, and the content of the signal is video stream data and control commands.

DVP (parallel port)

DVP is a parallel port transmission, the speed is slow, the transmission bandwidth is low, the use requires the following:

PCLK\sensor output clock--MCLK(XCLK)\external clock input--VSYNC\field synchronization--HSYNC\line synchronization--D[0:11]\parallel port data (can be 8/10/12bit data bit size )

PCLK: pixel point synchronization clock signal, each PCLK corresponds to a pixel point, which can be 48MHz; for clock signals, generally do packet processing to reduce interference to other signals. It is also necessary to add resistors and capacitors at the source to reduce overshoot And ringing, thereby reducing interference to other signals.

MCLK (XCLK): External clock input, which can be provided by the main control or crystal oscillator, determined by the sensor specification, which can be 24MHZ;

VSYNC: Frame synchronization signal, one signal per frame, the frequency is tens of Hz (30 Hz)

HSYNC: horizontal synchronization signal (frequency is tens of KHz)

Overview of LVDS output interface:

The LVDS output interface uses very low voltage swing (about 350mV) to transmit data through two PCB traces or a pair of balanced cables through differential, that is, low-voltage differential signal output. The LVDS output interface enables signals to be transmitted on differential PCB lines or balanced cables at a rate of several hundred Mbit/s. Due to the use of low voltage and low current driving methods, low noise and low power consumption are realized.

Composition of LVDS interface circuit

In the liquid crystal display, the LVDS interface circuit consists of two parts, namely the LVDS output drive circuit (LVDS transmitter) on the driver board side, and the LVDS input interface circuit (LVDS receiver) on the liquid crystal panel side. The LVDS transmitter converts the 17L level parallel RGB data signal and control signal output by the main control chip of the driver board into a low-voltage serial LVDS signal, and then transmits the signal to the liquid crystal through the flexible cable (line) between the driver board and the LCD panel The LVDS receiver on the panel side converts the serial signal into a TTL level parallel signal and sends it to the LVDS receiver on the LCD panel side. The LVDS receiver then converts the serial signal to a TTL level parallel signal. , Sent to the LCD screen timing control and row and column drive circuit.