As seen in figure 1, there are a growing number of sensor-based systems using a variety of sensing technologies. Some of these systems do not transfer large amounts of data; they are sensor detect and alert type transfers of minimal data.
However, other systems are capturing large amounts of data in order to handle the transfers efficiently. For example, a camera assist system used for lane detection or traffic sign recognition creates a dense data stream that needs to be transmitted from the camera to a processor for analysis and to a display for viewing.
In systems like these, the MIPI Camera Serial Interface (CSI) provides a protocol framework to pass data from the camera to the processor. The actual transmission is accomplished by using another MIPI specification, MIPI D-PHY, which is a physical layer transceiver specification. Using MIPI D-PHY means that the interface will operate at the lowest power and deploy at a minimal cost. MIPI Alliance develops specifications with flexible architectural definitions, recognizing that targeted implementations are necessary to realize an optimal combination of physical pins and transfer rates.
Figure 2 is one example of a targeted implementation; a simplified diagram of the camera-to-processor connection. The camera sub-assembly has the camera sensor and supporting circuitry for image capture and for organizing the image data for transmission using a D-PHY Tx macro.
The camera image is serialized and sent across to an Image Signal Processing sub-assembly containing the supporting circuitry for receiving the data – a D-PHY Rx macro. The physical connection between the Tx and Rx side is made using a MIPI interface. NXP designed such a system using the MIPI CSI-2 specification and a D-PHY hard macro provided by Mixel.