MIPI CSE℠

Developed by: Camera Working Group

The MIPI Camera Service Extensions (MIPI CSE℠) specification defines extended functions for MIPI Camera Serial Interface 2 (CSI-2®), including functional safety, security and other features. Functional safety functions were included in CSE v1.0, and security functions added in CSE v2.0.

By enabling these services, MIPI CSE helps to standardize and streamline the integration of high-performance image sensors in next-generation vehicles and IoT devices.

MIPI CSE is a component of MIPI Automotive SerDes Solutions (MASS), a standardized, end-to-end connectivity framework based on MIPI A-PHY for the integration of automotive image sensors and displays with built-in functional safety and security. The CSE specification can be used in automotive systems to achieve functional safety goals from ASIL B through to ASIL D.

The CSE specification was developed by the MIPI Camera Working Group and is available only to MIPI Alliance members. For information about becoming a member, visit Join MIPI.

Advantages

• Extends capabilities of the MIPI CSI-2 image sensor interface for automotive, industrial and other IoT use cases
• Supports functional safety as defined by the ISO 26262 standard
• A key component of the MIPI Automotive SerDes Solutions (MASS) connectivity framework

Fundamental Features

• Functional safety enablers
• Security enablers
• Extended Virtual Channel (eVC) for transmission of more data types
• Extended Data Type (eDT) to transmit higher-resolution image data
• For use with MIPI-approved PHYs

SEP and FSED Protocols

CSE services are implemented using either the Service Extension Packet (SEP) protocol or Frame-Based Service Extension Data (FSED) protocol. The two data service protocols differ in their approach – the SEP protocol adds additional headers and footers to each CSI-2 packet (or frame), whereas the FSED protocol adds additional CSI-2-based packets to each image frame. The choice of protocol gives implementation flexibility, particularly when implementing CSE services within legacy solutions.

SEP and FSED provide packetization and uniform delivery of MIPI CSI-2 image data over MIPI A-PHY, C-PHY, D-PHYand other MIPI-approved physical layer interfaces. The protocols allow image data transfer with functional safety and security over heterogeneous combinations of physical-layer interfaces, lane configurations and symbol rates.

When used with A-PHY®, the image content can be adapted using the A-PHY protocol adaptation layer for CSI-2 (MIPI PAL/CSI-2) to and from the SEP/FSED formats into A-PHY A-Packets either at SerDes bridges or by the image sensor and processor for end-to-end data transfer.

Functional Safety

The functional safety features enabled by MIPI CSE help automotive system designers build systems that meet the requirements laid out in the ISO 26262 standard from ASIL B to ASIL D. They include the following:

• Cyclic redundancy check (CRC) to detect data transmission errors
• Frame counter to detect frame loss or duplication
• Timeout monitoring to detect any loss of data between image sensors and processors

Functional safety test vectors are also available to streamline testing and implementation of image sensor interface.

Security

CSE security services enable authentication, integrity protection and (optional) encryption of image sensor data. They provide a high degree of flexibility to balance required security levels against processing efficiency, thermal regulation, and power consumption.The specification provides:

• Choice of ciphersuites. A "efficiency" ciphersuite providing AES-CMAC data integrity only (no encryption), targeted toward sensors with limited hardware resources. A "performance" ciphersuite providing AES-GMAC data integrity and optional AES-CTR encryption, targeted at sensors with dedicated hardware support.
• Choice of tag modes. Offering multiple tag mode options, allowing the implementer to choose how often the tag is computed and transmitted.
• Granular security controls. Providing highly granular ‘source-selective’ control over the different segments of the CSI-2 image frame to enable a “sliding scale” of security levels.

CSE security is uniquely effective in both its security extent and implementation flexibility.

When both security and functional safety service extensions are enabled, security is layered on top of functional safety—from a source (or transmitter) perspective, security is applied to the image data first, followed by the application of functional safety.

Resources