MIPI Interfaces: CSI vs. DSI

This article explores the world of MIPI (Mobile Industry Processor Interface) interfaces, focusing on the differences between two key types: MIPI CSI and MIPI DSI.

What is MIPI?

MIPI stands for Mobile Industry Processor Interface. It’s an organization, the MIPI Alliance, made up of leading companies in the mobile industry, including giants like Intel, Nokia, Samsung, Motorola, TI, and ST. The MIPI Alliance’s goal is to create open standards for interfaces used with mobile application processors. This standardization helps the industry innovate and bring new services to mobile users more quickly.

Figure 1: Common MIPI interfaces, showing connections between baseband and RFIC, application processors and image sensors, and application processors and display ICs.

MIPI CSI Interface Explained

CSI, which stands for Camera Serial Interface, is a high-speed serial interface designed for communication between a host processor and a camera module. Specifically, the MIPI CSI-2 interface is widely used.

Figure 2: The MIPI CSI-2 Interface.

Here are some key features of MIPI CSI-2:

• High-Performance: It provides a high-speed serial link between the image sensor and the application processor.
• D-PHY Physical Layer: It uses the D-PHY physical layer, supporting up to 4 data lanes to achieve data throughput of about 4 Gbps.
• Differential Clock: It uses one common differential clock line.
• I2C Control: A separate I2C interface is used for controlling camera functions.
• Packetized Transmission: MIPI CSI-2 supports packetized data transmission, which is helpful for line management, error detection, and error correction.

Benefits of MIPI CSI:

• Scalability
• Lower power consumption
• Improved reliability
• Lower overall system cost

MIPI DSI Interface Explained

DSI, or Display Serial Interface, is another high-speed serial interface. The DSI interface aims to provide efficient, low-power, and low-pin-count connectivity between an application processor and a display module (or a display bridge IC). It also uses the MIPI D-PHY as its physical layer.

Figure 3: The MIPI DSI Interface

Key features of MIPI D-PHY used in DSI:

• Data Lanes: It utilizes up to 4 data lanes along with 1 common differential clock line.
• Throughput: It can achieve throughputs of up to 1 Gbps.
• Single Stream: Pixel and data commands are serialized into a single physical stream between the processor and the display IC. The display IC sends status information back to the application processor.

Key Differences: MIPI CSI vs. MIPI DSI

While both CSI and DSI utilize the MIPI standard and often the D-PHY physical layer, they serve different purposes:

• CSI is focused on transferring image sensor data to an application processor, emphasizing high data rates and features for camera control and reliability.
• DSI is designed to send display data from the application processor to a display module, prioritizing efficient delivery of pixel and command data to drive the screen.

In summary, MIPI CSI focuses on capturing visual information, while MIPI DSI focuses on displaying it, both using similar underlying technologies for different ends.