CAN-BUS is a common industrial bus because of its long travel distance, medium communication speed and high reliability. It is widely used as the automotive diagnostic bus, and also commonly used on modern machine tools. This CAN-Bus shield gives the Arduino CAN-Bus capability, It uses the Microchip MCP2515 CAN controller with MCP2551 CAN transceiver, the CAN connection is via a standard 9-way sub-D for use with OBD-II cable, ideal for automotive CAN application. The shield also has a Micro SD card holder, which helps you store the diagnostic information in the SD card directly, making this shield ideal for data logging application.