Vehicle onboard diagnostics communication with exterior diagnostics unit using controller area network bus and universal serial bus

摘要

The exterior diagnostic unit (30) is host to the universal serial bus USB so that the coupling module (20) is a functional device. The transfer mode on the USB is 'bulk' mode. The inquiring time on the USB by the equipment (30) is of the order of 10 milliseconds. The coupling module (20) is connected to the controller area network CAN bus (11) via diagnostic connector at an end of the CAN bus and to USB bus so as to form logic links between a pair of unidirectional equipment terminals and corresponding module terminals. Each unidirectional terminal point is programmed so that the USB packet size that is delivered or collected is equal to 16 Octets. Communication between equipment (30), outside the automobile (1) and the automobiles onboard computers (10) is done by at least a controller area network CAN bus (11), in which the equipment is connected through a universal serial bus connection USB (31). The communication equipment includes a coupler module (21) connected to the CAN bus so as to avoid electrical reflections on it and to the USB bus. The equipment also includes means, for transmitting via the USB bus, CAN frames between the equipment (30) and computers (10) so that an application program executed in the equipment (30) is seen on CAN bus as a CAN subscriber. The coupling module (20) includes a first buffer memory in which data passes from or to the CAN bus. It has a second buffer memory through which passes the data to or from the USB bus and means of controlling the saturation of either bus.