Raspberry Pi CSI Camera Interface

The Raspberry Pi has a Mobile Industry Processor Interface (MIPI) Camera Serial Interface Type 2 (CSI-2), which facilitates the connection of a small camera to the main Broadcom BCM2835 processor. This is a camera port providing an electrical bus connection between the two devices. It is a very simple interface and with a little reverse engineering with an oscilloscope, it is possible to figure out the pinout. The purpose of this interface was to standardise the attachment of camera modules to processors for the mobile phone industry. The CSI-2 version of the interface was extremely popular and used on almost all the mobile phones and devices currently found. With increasing camera resolution, the bandwidth of data transferring from the camera to the processor also increases. The CSI-2 specification developed by the MIPI Alliance solves a number of problems that arise when large amounts of data require transfer to the processor.

MIPI CSI-2 version 1.01 supports up to four data lanes, where each lane has a maximum of 1 Gbps bandwidth, to provide a total bandwidth of 4 Gbps. In addition, the interface uses the least number of electrical connections to reduce PCB complexity. The data communication is one-way, from camera to processor. The D-PHY specification defines the physical hardware layer interface between a camera and a processor to facilitate the fast exchange of data. This is a low power, high-speed specification ideal for mobile and battery operated devices. It is also very scalable and the interface may have any number of "data lanes" depending upon the throughput requirement of the camera module.

Camera Connector

As you can see, the Raspberry Pi has a camera interface (ZIF 15) where a ribbon cable connects to establish the communication bus. The CSI connector consists of two smaller interfaces. The first interface is for the transfer of data and clock signals from the camera to the processor in one direction only. The second interface consists of SCL / SDA lines, which is a bidirectional control link.

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