Why EDP cable？
With the higher and higher display resolution, the traditional interfaces such as VGA and DVI can not meet people’s visual needs.
Then there are new digital interfaces, such as HDMI and DisplayPort. HDMI has a big advantage in the external interface, but DisplayPort adjusts its structure with its own advantages, and the gap is closing.
The internal interface of the traditional use of LVDS, LVDS face increasingly difficult high-resolution display, DisplayPort internal interface EDP was born, will gradually replace LVDS in the future
LVDS, or Low Voltage Differential Signaling, is a Low Voltage Differential Signaling interface. It is a digital video National Semiconductor developed by NS Company to overcome the disadvantages of high power consumption and EMI when transmitting broadband high bit rate data at TTL level.
Why learn EDP？
Understand EDP interface functions, and data packets and transmission methods, action points.
Through the study of EDP, analysis of EDP interface function, understand the design of the driver board, familiar with the EDP interface screen lighting and fault analysis.
What is EDP cable？
It is an internal digital interface based on the DisplayPort architecture and protocol. Suitable for tablets, laptops, all-in-one machines, the future of the new large-screen high-resolution mobile phones, the future will replace LVDS.
EDP Cable VS LVDS Cable
Now take an LG display LM240WU6 as an example of the transport advantages of EDP:
LM240WU6: WUXGA level resolution 1920 × 1200,24-bit color depth, 16,777,216 colors
You need 20 lanes with a traditional LVDS driver
Only 4 lanes are needed for EDP.
What are the advantages of EDP Cable？
Micro-packet structure, can achieve multi-data simultaneous transmission
High transmission rates, up to 21.6 Gbps in 4lanes
Smaller size, width 26.3 mm, height 1.1 mm, conducive to the thin products
No LVDS conversion circuit, simplified design
Smaller EMI (electromagnetic interference)
Strong copyright protection function
What are the components of EDP Cable？
Main Link:
It consists of 1-4 pairs of lanes, each of which is a pair of difference lanes;
Using AC coupling technology, the transmitter and the receiver have different common-mode voltage, so the interface can be made smaller;
The current transmission rate of each line is: 1.62/2.7/5.4 Gbps;
Each data line is data line, no clock line, reduce EMI;
ANXI8B/10B coding is adopted to improve the accuracy of data transmission
Function: Used to transmit all kinds of video data and audio data.
How Do I select the number of Lane?
How Main Link selects the number of Lane
The number of Lane required is based on the screen resolution and color depth
| Lane | 1 Lane | 1 Lane | 2Lanes | 2Lanes | 4Lanes | 4Lanes |
| Lane rate | 1.62 | 2.7 | 1.62 | 2.7 | 1.62 | 2.7 |
| Max capacity | 1.296 | 2.16 | 2.952 | 4.32 | 5.184 | 8.64 |
Bit rate requirement=pixel of clock rate*bpp
The Pixel of clock rate is fixed in the EDP and can be obtained by looking up the table.
Aux Ch: auxiliary channel
It is a bi-directional half-duplex transmission channel using AC coupled differential transmission
Adopt Manchester erii coding
Provides 1MBPS transmission rate and 15m transmission distance
Low latency, each transfer task has a time requirement of less than 500us
Role: for data transmission, Link Management, and device control with small bandwidth requirements
HPD: Hot Swap Detection Channel
A one-way channel for detecting whether the upper and lower devices are connected, and then realize the connection and interruption of the line.
EDID: extended display representation data used to store display parameters
DPCD: EDP configuration data connected to the link management layer for link configuration.