Methods of Peripheral Synchronization in Real-Time Cyber-Physical Systems

Real-Time Cyber Physical Systems (RT-CPS) utilize network clock and frequency synchronization, typically IEEE 1588 PTP or its derivatives, to agree on a common time and frequency on all nodes. The knowledge of common time and frequency is required for in-phase sampling and actuation in the distributed system, and for timestamping based on the global clock. Modern network enabled microcontrollers (NeMCU) and embedded application processors support (EAP) IEEE 1588 in hardware; however, it means that only the physical hardware clock in the network interface controller (NIC) is synchronized, not the actual embedded peripherals, such as A/D and D/A converters, digital I/O ports, timers, PWM modules, or secondary communication interfaces. It is the task of the developer to devise a hardware and software solution for peripheral synchronization. In the paper we investigate how modern NeMCUs and EAPs support peripheral synchronization, and how one can construct synchronized peripherals utilizing the features of hardware and proper software. The findings of the paper are demonstrated by analyzing the performance of a synchronized sampling system (sound acquisition system) and an extended timestamp unit.