I have implemented a redundant system with two PM592 ETH CPUs and a CI590 CS31 module using the High Availability library with different I/O modules. Now I am planning to add RS85 communication from the CPUs to different devices. The problem is that I also need the RS485 communication to be redundant i-e at a given time only the primary CPU will act as the master and send data and the data is synchronized with the secondary CPU using the HA library's data sync block. When changeover occurs the secondary CPU now acts as the master and continues transmission on the RS485 from the same sequence where the primary CPU faced a fault. Does the HA_CS31 Library usefull in this regard or not
No HA CS31 does not support external devices connected on RS485 directly.
However , there is one possibility. You can create logic to use primary bit to send and receive data. Primary and Secondary CPU data will get synced and during change over , secondary cpu will take over as per HA logic.