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MIPI A-PHY Specification Levels Up In-Vehicle Connectivity

EETE: Another key topic is MIPI A-PHY
protocol adaptation layers. What are
these PALs, and how will they impact
configuration options for automotive
system designers?
Nagpal: The MIPI PALs allow components to
map video, audio and control data to A-PHY’s
A-Packet format for transmission over long-
reach A-PHY networks. In this sense, the PAL
specifications serve as the “glue” that defines
the adaptations, flows and mechanisms
for individual higher-layer protocols to be
carried across A-PHY. The goal is to simplify
implementation of the higher-layer proto-
cols to become plug and play. The modular
approach helps designers contain their cost
of implementation. Plus, because of their
similarity in structure, additional protocols
are relatively easy to support, and innovation
can be sourced from a much broader group of
suppliers.
PALs for MIPI CSI-2 (Camera Serial Inter-
face), MIPI DSI-2 (Display Serial Interface)
and VESA (Video Electronics Standards A-PHY v2.0 is planned for the latter half of 2023, and the
Association) Embedded DisplayPort and
DisplayPort, as well as for lower-bandwidth MIPI A-PHY working group’s goal is to provide OEMs with a
interfaces, such as I²C and GPIO, have already clear path forward for cost-efficient product innovation.
been released. Also, the available PALs are
being continually updated. Another MIPI
PAL to enable the control and configuration are monitored at the protocol level to ensure EETE: Why is it advantageous to embed
of peripheral devices for up to 100 Mbps of errors and failures are detected at the appli- functional safety natively within sensors
Ethernet traffic over A-PHY v1.1 was released cation layer. Three main features undergird and ECU components themselves via
in 2022, and PALs for MIP I C and SPI are CSE’s FuSa functionality: MASS?
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forthcoming. • CRC-32 (cyclic redundancy check) with a Lasry: There are three primary reasons. First,
Hamming distance greater than or equal to 3 end-to-end is as close as possible to the
for ensuring that the image data captured by application—directly from the pixel source
sensors is accurate when received at ECUs in the sensor down to the pixel sink in the
• Detection of frame loss or duplication SoC—as opposed to link-based protection that
and assurance of continuity of video streams protects only from bridge to bridge. Second,
from cameras to ECUs—via a message end-to-end protection is PHY-agnostic. It can
counter in CSE v1.0 and via a frame counter be used over any PHY—A-PHY, C-PHY, D-PHY
in v2.0 (in development), for flexibility or any other MIPI-authorized PHYs (such as
of tradeoffs between overhead and error- Wi-Fi). And, third, there’s interoperability;
detection latency end-to-end protection must be interoperable
• Test-pattern generation and fault- across multiple vendors.
injection capability, for verifying proper FuSa and security historically have had to be
operation of the sensor’s CSI-2 interface for bolted onto designs afterward via proprietary
checking for latent faults solutions, so having these crucial capabilities
Building on this, the MIPI Security delivered natively within the components pro-
Working Group is working on a package of vides a stronger, seamless solution, delivering
Qualcomm’s Ariel Lasry specifications, including an update to CSE, key benefits of reduced cost and streamlined
that will enable application-based, end-to- integration and design time.
EETE: What are some of the other end security for protection of automotive MIPI evaluated the requirements defined
forthcoming MIPI specification updates camera data streams. Those specifications in ISO 26262 and embedded corresponding
that might enhance the industry’s ability are expected to be available for member FuSa-enabling features to detect packet loss,
to meet requirements for functional review early this year. Furthermore, whereas frozen links and loss of communication into
safety, security and data protection? CSE protects the data plane, MIPI Command both A-PHY and the upper-layer camera and
Ariel Lasry: The MIPI Camera Security and Control Interface Service Extensions display protocols, to help designers build
Extensions (CSE) specification is perhaps a (CCISE) protects the control plane. MIPI solutions that meet Automotive Safety
centerpiece of MIPI’s approach in this area. CCISE defines security extensions to apply Integrity Level requirements from ASIL B
Substantial FuSa (functional safety) capabili- data integrity protection and optional through ASIL D. ■
ties were built into the first version of CSE so encryption to I C-based command and con-
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that image data transferred from sensors to trol interfaces and features end-to-end FuSA Anne-Françoise Pelé is editor-in-chief of
ECUs and the data that control those sensors and security. EE Times Europe.

www.eetimes.eu | MARCH 2023