Backwards Compatibility of Single Pair Ethernet Cables

Abstract:
The Internet of Things (IoT) is more and more present in new buildings (BIoT) and factories (IIoT), with more sophisticated applications and devices, with huge demand for bandwidth and integration with management software tools (BMS, Dashboards, MES, ERP) into an All-IP network. One of the technology enablers will be Single Pair Ethernet with Ethernet chipsets, connectors, and the cables. This migration takes time and needs investments. It will not happen immediately in all IoT implementations. Nevertheless, it is possible to prepare the infrastructure to adopt the new generation of devices, even if for now the legacy equipment is still in use. It was investigated how the new SPE cables can be used with legacy bus protocols (Foundation Fieldbus, Profibus PA and PB, RS485, BacNet, Modbus, Canbus), comparing the design, electrical characteristics of primary performance criteria (capacitance, ohmic resistance, resistance unbalance) and secondary performances (attenuation, impedance, return loss, balance and especially the frequency range of transmission) of both legacy and SPE cables. Conclusion of that analysis shows that the SPE cables are backwards compatible with some important legacy protocols and can be used with legacy devices like CAN, RS485, Foundation Fieldbus H1 and Profibus PA, but not to Profibus DP. Additionally, the retrofit of old cables was also investigated, revealing to be a non-future proof initiative.