Polling

TurboModbus provides a fluent polling API that returns an Akka.Streams Source.

Basic Polling

Source<RegisterResponse, UniqueKillSwitch> source = client.Poll(
    TimeSpan.FromSeconds(10),
    poll => poll
        .Registers(1000, 4)       // outdoor temp, avg temp, buffer temp, ...
        .Registers(1050, 2)       // supply temp, return temp
        .Registers(4122, 2, inputRegister: true));  // electrical power

Each tick reads all configured register groups sequentially (Modbus TCP is serial) and emits a RegisterResponse per group.

Change Detection

Apply the built-in ChangeDetectionStage to filter to only changed values:

using Akka.Streams;
using Akka.Streams.Dsl;

var mat = system.Materializer();

var (killSwitch, done) = client.Poll(TimeSpan.FromSeconds(10), poll => poll
        .Registers(1000, 4)
        .Registers(1050, 2))
    .Via(new ChangeDetectionStage())
    .ToMaterialized(
        Sink.ForEach<RegisterResponse>(r =>
            Console.WriteLine($"[{r.Address}] changed")),
        Keep.Both)
    .Run(mat);

// Stop polling
killSwitch.Shutdown();
await done;

The stage holds previous values internally and only pushes downstream when register content actually changes.

RegisterResponse

public sealed record RegisterResponse(ushort Address, ushort[] Registers);

The Address is the start address of the read request. Registers contains the raw 16-bit values. Interpret them according to your device's register map (float, int, bool, etc.).

KillSwitch

The Source is materialized with a UniqueKillSwitch. Call Shutdown() to stop polling cleanly. The underlying TCP connection is managed by the ModbusClient — stopping the poll source does not disconnect the client.