4bffe879c5
Two driver-side filters that ≥5 of 6 surveyed vendors expose: 1. Per-tag Deadband (double?, on ModbusTagDefinition) — when set, the PollGroupEngine onChange callback suppresses publishes whose distance from the last-published value is below the threshold. Reduces wire traffic to OPC UA clients on noisy analog signals (flow meters, temperatures). Numeric scalar types only — Bool / BitInRegister / String / array tags publish unconditionally. 2. WriteOnChangeOnly (bool, on ModbusDriverOptions) — when true, the driver short-circuits writes whose value matches the most recent successful write to that tag. Saves PLC bandwidth on clients that re-publish the same setpoint every scan. Cache invalidates on any read that returns a different value, so HMI-side changes don't get masked. Both default off so existing deployments see no behaviour change. Implementation: - ShouldPublish guard wraps the existing OnDataChange invocation. First sample always passes through (no baseline); subsequent samples compare via Convert.ToDouble for the cross-numeric-type math. - IsRedundantWrite check at the top of WriteAsync; on success the cache is populated. Object.Equals handles boxed-numeric equality; arrays are excluded (reference-equality would never match anyway). - ReadAsync invalidates the WriteOnChangeOnly cache when the new value differs from the cached last-written value. Tests (5 new ModbusSubscribeOptionsTests): - Deadband suppresses sub-threshold changes (100 → 102 → 106 → 107 with deadband=5 publishes 100 and 106 only). - Deadband=null still publishes every change. - WriteOnChangeOnly suppresses 3 identical 42 writes (only first hits wire). - WriteOnChangeOnly default false hits the wire every time. - Read-divergence cache invalidation: external panel write to 99, our client's re-write of 42 must NOT be suppressed. 220/220 unit tests green; existing ProtocolOptions tests hardened against probe-loop noise by disabling the probe in their fixtures.
6.0 KiB
6.0 KiB