For the full video of this presentation, please visit: https://www.edge-ai-vision.com/2023/10/introduction-to-the-csi-2-image-sensor-interface-standard-a-presentation-from-the-mipi-alliance/ Haran Thanigasalam, Camera and Imaging Consultant to the MIPI Alliance, presents the “Introduction to the MIPI CSI-2 Image Sensor Interface Standard” tutorial at the May 2023 Embedded Vision Summit. By taking advantage of select features in standardized interfaces, vision system architects can help reduce processor load, cost and power consumption while gaining flexibility to source components from multiple vendors. In this presentation, Thanigasalam introduces the standardized MIPI CSI-2 imaging conduit solution for interfacing image sensors to processors. Thanigasalam explains how the solution supports basic operations of a camera sensor, including physical frame transport options and orthogonal commands for autoexposure, autofocus, auto white balance and event detection. He also introduces command sets to help bring up and tune sensors. In addition, Thanigasalam explores provisions to alleviate RF emissions, enable aggregation of data from multiple remote sensors and alleviate the need for dual voltage signaling to avoid electrical overstress issues. He also touches on emerging support for frame transport using WiFi.

1. Introduction to the MIPI CSI-2
Image Sensor Interface Standard
Haran Thanigasalam
Camera & Imaging Consultant
MIPI Alliance
1

2. • MIPI Alliance & Standardization of CSI-2 Frame Format
• Scope of Applications Spanning Mobile and Beyond Mobile Platforms
• Low Energy Pixel Transport Solutions & Imaging System Considerations
• Native Support for Long Reach & Provisions to Help Alleviate Emissions
• Summary with Technical Insights Track Coverage
Topics
2
© 2023 MIPI Alliance, Inc.

3. MIPI Alliance and Camera Serial Interface
(CSI-2) Standardization
3
• MIPI is a global, collaborative
organization founded in 2003
that comprises 400+ member
companies spanning the
mobile and mobile-influenced
ecosystems.
• MIPI’s mission is to provide
the hardware and software
interface specifications device
vendors need to create state-
of-the-art, innovative devices
while accelerating time-to-
market and reducing costs.
© 2023 MIPI Alliance, Inc.

4. • Packet Header (PH) contains Frame Data Type, Virtual Channel
protected by Error Checking and Correction or replication.
• The Dynamic Long Packet is structured as a best effort carrier
with a Cyclic Redundancy Checker (CRC).
• Complementary specifications supporting CSI-2 include:
physical layer transport (A/C/D-PHY & I3C), Functional Safety
and Security (CSE), Unified Imaging SW Drivers (CCS & DisCo),
and Conformance Test Suite (CTS).
CSI-2 Frame Format & Complementary
Specifications
4
SNS & APP
Covenant
Low Energy
Transport
Applications
Driven
Provisions
D-PHY C-PHY A-PHY I3C CTS CSE (SEC) CCS DisCo
CSE (FS)
PH
Embedded Data
Dynamic Long Packets
(Pixel Data)
Embedded Data
CRC
SNS = Sensor | APP = Application Processor | FS = Functional Safety | SEC = Security
© 2023 MIPI Alliance, Inc.

5. Beyond Mobile Transition: Differential Pulse
Code Modulation for Street Sign Detection
5
Original 12-8-12 12-10-12
• Pivotal timeframe in the evolution of CSI-2
development
• Qualified 5 degree slanted edge input image with
low, medium, and high illumination levels
• MTF frequency response analysis closely track the
original (HI/MI/LI X LC/MC/HC)
• Reduce maximum absolute error of single-bit
change in pixel value by a factor of 4.43x
• Transport SerDes network bandwidth reduction &
system cost reduction
Compression
Artifacts
© 2023 MIPI Alliance, Inc.

6. Scope of Applications Spanning Mobile and
Beyond Mobile Platforms
6
CONSUMER
Mobile Smart Phones
Client Products (AIO | 2:1 | Laptops |
Tablets)
Smart Homes (Lights | Appliances |
Irrigation)
Home Security ( Doorbell | Property
Surveillance)
Emotional Metadata
Tunable Avatars
COMMERCIAL
Smart Retail (Autonomous Checkout)
Commercial Surveillance (Abnormal
Behavior)
Airport Retinal Scan
Biometric Access Control | Payments
Fire Detection |Parking Monitors
Autonomous Transportation (Land | Water
| Air)
Medical & Industrial Client Products
Commercial Drones & Robotics
INFRASTRUCTURE
Robotics (Perception & Decision Making)
Smart Municipal City (Abnormal Behaviors)
Highway Traffic Monitoring (Accidents)
Public Transportation (Abnormal Behavior)
Long Range Perimeter Surveillance
(Security)
Environmental Monitoring (Fires |
Earthquake)
Space Exploration (Rover)
© 2023 MIPI Alliance, Inc.

7. 7
• Point-to-point unidirectional connection
• Forwarded differential half-rate periodic clock
• Differential pixel data sampling
• SoC physical imaging ports are frozen at pin
level
• Variable link rate matched to SNS pixel clock
• Popular Camera Sensor (SNS) configurations:
• X4 (4 Data Lanes comprising 10 pins)
• X2 (2 Data Lanes comprising 6 pins)
• X1 (1 Data Lane comprising 4 pins)
SNS
X4
SNS
X2
SNS
X1
RX_DAT
RX_CLK
A
P
P
CCI
CSI-2 Over D-PHY Low Energy Pixel Transport
RX_DAT
© 2023 MIPI Alliance, Inc.

8. • Deployment of multiple classes of CSI-2
camera sensors using C/D-PHY transport.
• The CSI-2 over C-PHY supports variable
link rate where the clock is recovered
from the ternary symbol transitions over
3 wires.
• The CSI-2 over C-PHY offers an effective
bandwidth coding gain of 2.28 by
transporting 16 bits over 7 symbols.
• Select camera sensors may support CSI-2
over Combo C/D-PHY signaling since the
pins are electrically compatible.
• Illustration depicts a 6-pin CSI-2 over D-
PHY X2 (2 Lane) Port, and a CSI-2 over
C-PHY T2 (2 Lane) Port.
CSI-2 Over C-PHY Low Energy Transport
8
Embedded
Clock & Data
Periodic Clock & Data
© 2023 MIPI Alliance, Inc.

9. 9
© 2023 MIPI Alliance, Inc.
• Impact of gaussian errors on ternary signaling transport
• Provisions to facilitate run-time recovery:
• CSI-2 Packet Header Replication
• Camera Sensor TX: 3_44444_3
• Application Processor RX Detection: X_44444_3
Camera Link Error Mitigation
© 2023 MIPI Alliance, Inc.

10. • Imaging system with an 18-pin
SoC
• Dynamic link rate
• Frozen vs logical ports
• Reduction of switching rate
• Virtual channels (4 / 16 / 32+)
• CSI-2 over D-PHY lane channel
rates:
• Standard: 9 Gbps
• Short: 11 Gbps
• CSI-2 over C-PHY lane channel
rates:
• Standard: 6 GSps (13.7 Gbps)
• Short: 8 GSps (18.3 Gbps)
Imaging System Architecture Considerations
10
X4
X1
SoC
CSI-2
D-PHY
SoC
CSI-2
C-PHY
T1
…
X1
T1
T1
T1
T1
T1
T2
T1
T1
T1
T1
T2
T1
T1
T2
T3
T3
© 2023 MIPI Alliance, Inc.

11. Latency Reduction and Transport Efficiency
(LRTE) Benefits
11
Imaging system benefits: Improve sensor aggregation, alleviate dual voltage signaling, support long reach
Legacy Packet Transfers using End of Transmission (EoT), Low Power Signaling (LPS),
and Start of Transmission (SoT) delimiters
LRTE replaces legacy EoT, LPS, SoT with an Efficient Packet Delimiter (EPD)
© 2023 MIPI Alliance, Inc.

12. Power Spectral Density Reduction
Measurements
12
Imaging system benefits: Pseudo random binary sequence to help reduce shielding costs
© 2023 MIPI Alliance, Inc.

13. • MIPI CSI-2 protocol had the first mover advantage with smart phones, and continues to advance
for beyond mobile product platforms.
• Leveraging the established infrastructure, CSI-2 is universally used by camera sensors.
• Capabilities and features developed for computer vision applications will be covered in the
Technical Insights Track:
• Always On Sentinel Conduit for Inferencing
• Integrated & External Smart Region Of Interest
• Unified Serial Link with Encapsulation Support
• Multi Pixel Compression (evolved Differential Pulse Code Modulation)
• Welcome inputs on any additional MIPI CSI-2 protocol provisions that may be helpful for beyond
camera sensors mapped to emerging vision applications (i.e. LiDAR, Radar, Sonar, and FLIR).
Summary
13
© 2023 MIPI Alliance, Inc.

14. 14
Resources
https://www.mipi.org/specifications/csi-2
© 2023 MIPI Alliance, Inc.

15. Thank you
Contact Information: civ-ig@mipi.org
15
© 2023 MIPI Alliance, Inc.