The parallel camera interface, Camera Parallel Interface(CPI), is an interface for camera modules and image sensors specified by the MIPI Alliance. It consists of an I2C bus for interface control and a parallel interface for image data.
The parallel interface is formed by a parallel 8-bit link connecting the bus to the image sensor. The image sensor itself generates the vertical sync signal, the horizontal reference signal and the timing signal for the pixel clock. It is a unidirectional interface where all signals from the camera module are transmitted to the microcontroller( MCU). The image data is transmitted at each rising edge of the pixel clock. The horizontal reference signal appears after each scanned line and the signal for vertical synchronization at the end of an image.