Camera Serial Interface Explained
The Camera Serial Interface (CSI) is a specification of the Mobile Industry Processor Interface (MIPI) Alliance. It defines an interface between a camera and a host processor.
The latest active interface specifications are CSI-2 v4.1 (April 2024), CSI-3 v1.1 (March 2014) and CCS v1.1.1 (April 2023).[1] [2] [3]
Standards
CSI-1
CSI-1 was the original standard MIPI interface for cameras. It emerged as an architecture to define the interface between a camera and a host processor. Its successors were MIPI CSI-2 and MIPI CSI-3, two standards that are still evolving.
CSI-2
The MIPI CSI-2 v1.0 specification was released in 2005. It uses either D-PHY or C-PHY (Both standards are set by the MIPI Alliance) as a physical layer option. The protocol is divided into the following layers:
- Physical Layer (C-PHY/D-PHY)
- Lane Merger Layer.
- Low Level Protocol Layer.
- Pixel to Byte Conversion Layer
- Application Layer
In April 2017, the CSI-2 v2.0 specification was released. CSI-2 v2.0 brought support for RAW-16 and RAW-20 color depth, increase virtual channels from 4 to 32, Latency Reduction and Transport Efficiency (LRTE), Differential Pulse-Code Modulation (DPCM) compression and scrambling to reduce Power Spectral Density.[4]
In September 2019, the CSI-2 v3.0 specification was released. CSI-2 v3.0 introduced Unified Serial Link (USL), Smart Region of Interest (SROI), End-of-Transmission Short Packet (EoTp) and support for RAW-24 color depth.[5] [6]
CSI-3
MIPI CSI-3 is a high-speed, bidirectional protocol primarily intended for image and video transmission between cameras and hosts within a multi-layered, peer-to-peer, UniPro-based M-PHY device network. It was originally released in 2012 and got re-released in version 1.1 in 2014.[7]
CCS
The Camera Command Set (CCS) v1.0 specification was released on November 30, 2017. CCS defines a standard set of functionalities for controlling image sensors using CSI-2.[8] [9]
Technology & speeds
For EMI reasons the system designer can select between two different clock rates (a and b) in each of the M-PHY speed levels.[10]
M-PHY speed | Clock rate | Bit rate |
---|
Gear 1 | G1a | 1.25 Gbit/s |
G1b | 1.49 Gbit/s |
Gear 2 | G2a | 2.5 Gbit/s |
G2b | 2.9 Gbit/s |
Gear 3 | G3a | 5 Gbit/s |
G3b | 5.8 Gbit/s | |
See also
External links
Notes and References
- Web site: MIPI Camera Serial Interface 2 (MIPI CSI-2). 4 January 2017. MIPI Alliance. https://web.archive.org/web/20190928110213/https://mipi.org/specifications/csi-2. 28 September 2019. live.
- Web site: MIPI Camera Serial Interface 3 (MIPI CSI-3). 4 January 2017. MIPI Alliance. https://web.archive.org/web/20190928105228/https://mipi.org/specifications/csi-3. 28 September 2019. live.
- Web site: MIPI Camera Command Set (MIPI CCS). 12 November 2017. MIPI Alliance. https://web.archive.org/web/20190702114413/https://www.mipi.org/specifications/camera-command-set. 2 July 2019. live.
- Web site: MIPI Alliance Expands Popular CSI-2 Camera Specification Beyond Mobile. April 5, 2017. MIPI Alliance. https://web.archive.org/web/20190928105225/https://mipi.org/node/828. September 28, 2019. live.
- Web site: New Version of Most Widely Used Camera and Imaging Interface—MIPI CSI-2—Designed to Build Capabilities for Greater Machine Awareness. September 26, 2019. MIPI Alliance. https://web.archive.org/web/20190928105225/https://www.mipi.org/new-version-of-widely-used-camera-imaging-interface-mipi-csi-2. September 28, 2019. dead.
- Web site: VIP Central > MIPI CSI-2 v3.0 is here! – The industry's First Comprehensive Solution for 5G, Imaging, Surveillance and Automotive. blogs.synopsys.com. en-US. 2019-09-28. 2019-09-04. https://web.archive.org/web/20190904213310/https://blogs.synopsys.com/vip-central/. live.
- Web site: MIPI Camera Serial Interface 3 (MIPI CSI-3) . 2018-02-07 . 2018-02-07 . https://web.archive.org/web/20180207122402/https://www.mipi.org/specifications/csi-3 . live .
- Web site: MIPI Alliance Releases MIPI CCS, a New Specification that Streamlines Integration of Image Sensors in Mobile Devices. November 30, 2017. MIPI Alliance. https://web.archive.org/web/20190928105225/https://www.mipi.org/node/1306. September 28, 2019. live.
- Web site: An Interface to Make Installing Image Sensors Easier. 2017-11-30. Electronic Design. en. 2019-09-28. 2019-09-28. https://web.archive.org/web/20190928105217/https://www.electronicdesign.com/embedded-revolution/interface-make-installing-image-sensors-easier. live.
- Web site: Understanding MIPI Alliance Interface Specifications . 2018-02-07 . 2023-11-10 . https://web.archive.org/web/20231110053339/https://www.electronicdesign.com/technologies/communications/article/21799475/understanding-mipi-alliance-interface-specifications . live .