MIPI CSI-2®, originally introduced in 2005, is the world’s most widely implemented embedded camera and imaging interface. It has achieved widespread adoption for its ease of use and ability to support a broad range of high-performance applications, including 1080p, 4K, 8K and beyond video, and high-resolution photography.
Designers should feel comfortable using MIPI CSI-2 for any single- or multi-camera implementation in far-ranging application spaces such as mobile, augmented and virtual reality, drones, the Internet of Things (IoT), medical devices, industrial systems, automobiles and client devices such as tablets, notebooks and all-in-ones.
The CSI-2 specification is available only to MIPI Alliance members. For information about joining MIPI Alliance, visit Join MIPI.
CSI-2 is lane-scalable and typically implemented on either a MIPI C-PHY or MIPI D-PHY physical-layer interface for shorter-reach applications but also can be implemented over the MIPI A-PHY long-reach SerDes interface (up to 15m) for use in such applications as automotive advanced driver-assistance systems (ADAS) and in-vehicle infotainment, as well as industrial IoT. The newest version, v4.0, is also the first to support transmission of CSI-2 image frames over the low-cost, low-pin-count MIPI I3C/I3C Basic two-wire interface. All versions of CSI-2 are also backward compatible with previous versions.
MIPI CSI-2 v4.0, released in late 2021, delivers significant updates designed to enable greater capabilities for machine awareness across multiple application spaces. These new features include:
Always-On Sentinel Conduit (AOSC), which enables always-on machine vision systems in which combinations of ultra-low-power image sensors and video signal processors (VSPs) can continuously monitor their surrounding environments and then wake their higher-power host central processing units (CPUs) only when significant events happen. AOSC enables image frames to be economically streamed from an image sensor to a VSP over a low-power MIPI I3C bus in a highly efficient manner, with scaling options to add extra I3C lanes and bandwidth as defined by the I3C specification.
Multi-Pixel Compression (MPC), which provides optimized pixel compression for the latest generation of very-high-resolution Tetra-Cell and Nona-Cell image sensors with multi-pixel color filter arrays (CFAs).
RAW28 color depth pixel encoding, which supports unprecedented image quality and superior signal-to-noise (SNR) ratio in the next generation of high-dynamic-range automotive image sensors for safety-critical applications. (Previous versions offer support for up to RAW 24.)
The CSI-2 interface offers a wide range of other valuable performance attributes:
The option to use up to32 virtual channelsaccommodates the proliferation of image sensors with multiple data types, and supports multi-exposure and multi-range sensor fusion for applications such as enhanced collision avoidance in automotive.
Latency Reduction and Transport Efficiency (LRTE)provides image-sensor aggregation without adding to system cost; facilitates real-time perception, processing and decision-making; and optimizes transport to reduce the number of wires, toggle rate and power consumption.
Differential Pulse Code Modulation (DPCM) compressionreduces bandwidth while delivering superior SNR images devoid of compression artifacts for mission-critical vision applications.
Scramblingreduces Power Spectral Density (PSD) emissions, minimizes radio interference and allows further reach for longer channels.
Smart Region of Interest (SROI)for analyzing images, inferencing algorithms and making better deductions could enable machines on a factory floor, for example, to more quickly identify potential defects on a conveyor belt, or medical devices to more surely recognize anomalies such as tumors.
Unified Serial Link (USL)encapsulates connections between an image sensor module and application processor to reduce the number of wires needed in IoT, automotive and client products for productivity and content creation, such as all-in-one and notebook platforms.
The capability of theCamera Control Interface (CCI) to work with the MIPI I3C/I3C Basicinterface supports advanced imaging performance requirements for auto focus and optical image stabilization (OIS), among other applications.