Clock synchronization of PTP-based devices through PROFINET IO networks

The paper deals with IEEE1588 PTP-based devices which are installed in industrial plants together with PROFINET IO Class C. In fact, devices with PTP for clock synchronization (e.g. LXI instruments, Ethernet/IP nodes etc.) exhibit noticeable time errors if directly connected to the PROFINET infrastructure. In the paper, possible architectures to overcome this limitation are evaluated (i.e boundary clock), then an intelligent clock synchronization converter is proposed. The core idea is to create a black-box that does not require configuration neither of the PTP-based nodes nor of the host plant. The proposed converter has been applied to a PROFINET IO network that hosts PTP-based devices. Preliminary results show that, if compared with a direct connection of PTP-based nodes, the converter worsens the synchronization accuracy of less than 10 ns.