Search Results

Multiplexing systems have been used in automobiles for the past decade. The use of these systems has allowed manufacturers to reduce wiring harness size, eliminate redundant sensors, and achieve a level of communication not available before. While most applications of multiplexing have been inter-modular communication, there exist many more opportunities to utilize multiplexing. These opportunities include multiplexing various user activated/interacted switches, sensors, and actuators. Multiplexing of this type is defined by the SAE as a low speed sensor/actuator bus, or Class “A” bus. The Class “A” bus addresses issues, such as: the challenge of handling increasing wiring complexity, incorporating diagnostics and testability into automotive electronic designs, facilitating the use of new switch and actuator technologies, and allowing a higher degree of systems design flexibility.

This paper describes a cost effective, second generation J1850 link device that enables a standard microcontroller to communicate over the J1850 bus. This device interacts with the microcontroller over an industry standard SPI Port. The device handles the vast majority of bus interaction only requiring the microcontroller to interact with the J1850 Bus at a high level. An overview of the device is presented. A short review of the J1850-VPW Bus is reviewed. Also explained is how to transmit messages, receiving messages, bus monitoring options, Power Down Mode, how High Speed Mode works and special diagnostic features.