Software-Based AUTOSAR-Compliant Precision Clock Synchronization Over CAN

Modern cars are characterized by a growing number of sensors, actuators, and advanced driver assistance systems that require a synchronized view of the time. These devices are typically interconnected by CAN, which is still the most important in-vehicle network. Precise clock synchronization over CAN is difficult due to the properties of the bus, and current approaches often use dedicated hardware or proprietary software solutions. A few years ago, however, the AUTomotive Open System ARchitecture (AUTOSAR) development alliance published a standardized synchronization method. In this article, we investigate what synchronization precision can be realistically achieved in a real-world automotive hardware and software environment. This involves pure software timestamping, standard CAN controllers without hardware modifications, and a typical automotive real-time operating system. We evaluate several approaches to reduce the synchronization jitter using filtering and optimizing the timestamping procedure. Experiments show that, ultimately, a precision better than 50μs can be achieved with a fully AUTOSAR-compliant software implementation.