Camera Serial Interface
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 specification is CSI-3 which was released in 2012.[1]
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
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.[2]
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.[3]
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 |
References