Raspberry Pi Flexible Flat Cable (FFC) connectors
In Raspberry Pi, there are two flexible Flat Cable (FFC) connectors (S2 & S5).
S2, near to the micro USB connector, is the Display Serial Interface (DSI). It allows low-level interfacing with LCDs and other displays with Raspberry Pi. It is a 15-pin surface mounted flexible flat connector, providing two data lanes, one clock lane, 3.3V and GND.
S5, located between LAN and HDMI connector, is the MIPI Camera Serial Interface 2 (CSI-2) interface connector for camera modules. It is a 15-pin surface mounted flat flexible connector, providing two data lines, one clock lane, bidirectional control interface compatible with I2C, 3.3V and GND.
The data transmission interface in CSI is unidirectional differential serial interface with data and clock signals; the physical layer of this interface is the MIPI Alliance Standard for D-PHY.
The above figure illustrates connections between CSI-2 transmitter and receiver, which typically are a camera module and a receiver module, part of the mobile phone engine. The control interface is a bi-directional control interface compatible with I2C standard.