Hello everyone, I am Pi Ge! Have you ever wondered how mobile phone screens display images? How do televisions receive high-definition signals? How does an industrial control screen communicate with the system?
The answer lies in various display interface technologies!
Common display interfaces, such as LVDS, DSI (MIPI DSI), and HDMI, may seem like mere “data lines” or “interface types,” but in reality, each interface is backed by a complete technical system, divided into two key parts:
1. The “Two-Layer Architecture” of Display Interfaces
Any display interface essentially includes two core levels:
| Level | Name | Function | Analogy |
|---|---|---|---|
| Level 1: Protocol Layer | Display Control Protocol | Defines how image data is organized, how control commands are transmitted, how synchronization refresh occurs, etc. | Like a “language,” solving “what to say and how to say it” |
| Level 2: Physical Transmission Layer | Signal Transmission Mechanism | Defines how signals are transmitted over wires/cables, such as differential signals, voltage swing, transmission rate, etc. | Like a “telephone line/network cable,” solving “how to transmit stably” |
A complete display system = Protocol Layer (Content) + Physical Transmission Layer (Channel)
Next, we will break down the three major display interfaces: LVDS, DSI (MIPI DSI), HDMI, analyzing their technical details and differences from these two structural layers.
2. LVDS (Low Voltage Differential Signaling) – The “Veteran” of Industrial and Automotive Applications
Application Scenarios
- Industrial HMI displays (e.g., PLC control screens)
- Automotive dashboards
- Laptops (early models)
- Short to medium distance screen driving
Protocol Layer: No Unified Standard, Typically Customized
- LVDS itself is merely a differential signal transmission technology and does not define a “display protocol”;
- It is typically used to transmit raw pixel data (e.g., RGB) but does not include synchronization signals, control commands, data formats, and other high-level information;
- Often requires additional chips or controllers to handle timing, synchronization, format conversion, etc.;
- The protocol layer is usually customized or relies on external logic implementation.
Summary: LVDS is a “mover,” but how the “package is packed” relies on others.
Physical Transmission Layer: Low Voltage Differential Signals, Driven by Chips
| Feature | Description |
|---|---|
| Signal Type | Differential signals (positive and negative pairs) |
| Voltage Swing | Approximately 350mV (low voltage, low power consumption) |
| Transmission Method | Multiple pairs of differential lines (e.g., 3 data + 1 clock) |
| Transmission Rate | Single channel can reach hundreds of Mbps to 1Gbps+ |
| Driver Solutions | Common chips include TI’s SN65DSI83, Maxim’s DS90UB series |
| Transmission Medium | PCB traces or short-distance cables |
Summary: The physical layer of LVDS is a low-voltage differential transmission technology, but there is no unified PHY standard, relying on dedicated driver chips for implementation.
3. DSI (MIPI DSI) – The “Dedicated Highway” for Mobile Screens
Application Scenarios
- Smartphones, tablets
- Automotive digital displays / central control screens (high-end)
- Embedded display systems
Protocol Layer: Standardized “Display Language,” Powerful Functionality
DSI is a standardized display protocol established by the MIPI Alliance, specifically optimized for mobile devices. It defines:
- How image data is packaged (e.g., RGB/YUV formats)
- How control commands are transmitted (e.g., setting resolution)
- How synchronization signals are handled (VSYNC/HSYNC)
- How to enter low power mode, etc.
Summary: DSI is the “standard language” for mobile displays, with a complete protocol and rich functionality!
Physical Transmission Layer: MIPI D-PHY, High Speed + Low Power Dual Mode
| Feature | Description |
|---|---|
| Signal Type | Differential signals (similar to LVDS) |
| Transmission Mode | Dual mode: High-speed mode HS (for images, rates up to 6 Gbps/lane) + Low-power mode LP (for control commands) |
| Number of Lanes | Supports 1-4 data lanes + 1 clock lane |
| Encoding Method | Typically 8b/10b encoding, ensuring transmission reliability |
| PHY Standard | MIPI D-PHY (standardized physical layer protocol) |
| Transmission Medium | PCB differential lines (high-speed communication within devices) |
Summary: The physical layer of DSI is MIPI D-PHY, the highway for mobile displays, supporting high-speed transmission + low-power control.
4. HDMI (High Definition Multimedia Interface) – The “All-in-One Interface” for TVs and Audio-Visuals
Application Scenarios
- Televisions, monitors, projectors
- Game consoles, set-top boxes, Blu-ray players
- Consumer devices requiring audio-video synchronization
Protocol Layer: Most Comprehensive, Integrated Audio-Video + Control
The HDMI protocol layer includes:
| Function | Description |
|---|---|
| Video | Supports RGB / YCbCr, various pixel formats and color depths (8/10/12bit) |
| Audio | Multichannel LPCM, Dolby, DTS, etc. |
| Control Protocol | CEC (Consumer Electronics Control), ARC/eARC (Audio Return Channel) |
| Synchronization and Protection | HDCP digital copyright protection, EDID display information exchange |
| Advanced Features | HDMI 2.1 supports dynamic refresh rates (VRR), FRL new physical layer, etc. |
Summary: HDMI is the “all-rounder” for audio-video transmission, with a very complete protocol, supporting audio-video synchronization and intelligent control.
Physical Transmission Layer: TMDS, the “Stable Channel” for High-Definition Signals
| Feature | Description |
|---|---|
| Signal Type | Differential signals (TMDS encoding) |
| Channel Configuration | 3 data channels + 1 clock channel = 4 pairs of differential lines |
| Transmission Method | Constant high-speed mode (no low-power mode) |
| Encoding Method | TMDS (minimized transition encoding, reducing EMI) |
| Voltage Swing | Approximately 350mV differential |
| PHY Standard | Embedded in the HDMI standard, i.e., TMDS physical layer |
Summary: The physical layer of HDMI is the standardized TMDS transmission mechanism, the “dedicated highway” for audio-video signals.
5. Comparative Table of the Three Major Interfaces
| Item | LVDS | MIPI DSI (DSI) | HDMI |
|---|---|---|---|
| Main Applications | Industrial screens, automotive instruments, laptops | Smartphones, tablets, embedded devices | Televisions, projectors, set-top boxes |
| Protocol Layer | ❌ No unified protocol, typically customized | ✅ Standardized (MIPI DSI protocol)Comprehensive functionality, supports control and data | ✅ StandardizedSupports audio-video + HDCP + CEC, etc. |
| Physical Layer | ❌ No unified PHY, relies on driver chips | ✅ Standardized (MIPI D-PHY)Supports HS / LP dual mode | ✅ Standardized (TMDS)Constant high-speed transmission |
| Signal Type | Differential signals (low voltage) | Differential signals (D-PHY) | Differential signals (TMDS encoding) |
| Transmission Mode | Single high-speed | Dual mode: high-speed + low power | Single high-speed |
| Transmission Medium | PCB / short cables | Internal differential lines of devices | HDMI standard cables (Type-A / C / D) |
| Advantages | Strong anti-interference, mature and stable | Mobile optimization, low power consumption, high integration | Integrated audio-video, strong versatility |
Choosing the right interface can yield twice the result with half the effort!
| Interface | Who is it suitable for? | Core Feature in One Sentence |
|---|---|---|
| LVDS | Industrial control, automotive, traditional displays | Differential signal old technology, stable and anti-interference, but protocol and PHY are not unified |
| DSI (MIPI DSI) | Smartphones, embedded devices | Dedicated for mobile displays, both protocol and physical layer are standardized, efficient and low power |
| HDMI | Televisions, audio-visual equipment | All-round player for audio-video, strong protocol, stable transmission, standard for consumer electronics |