Camera Serial Interface

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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]



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.


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:

  1. Physical Layer (C-PHY/D-PHY)
  2. Lane Merger Layer.
  3. Low Level Protocol Layer.
  4. Pixel to Byte Conversion Layer
  5. Application Layer


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[edit]

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