Async I/O (C#)

Core async APIs take CancellationToken and return Task / ValueTask. Typed async classes (AsyncDmm, etc.) mirror the sync surface with *Async method names.

Mock quick start

using InstrumentComponents.Catalog;
using InstrumentComponents.Kind;
using InstrumentComponents.Mock;

var fixture = ScriptedFixture.Builder()
    .Idn("Acme", "DMM1", "SN1", "1.0")
    .Kinds(InstrumentKind.Dmm)
    .OnQuery(":MEAS:VOLT:DC?", "1.0")
    .Build();

var catalog = DeviceCatalog.FromFixture("mock://dmm", fixture);
var dmm = await catalog.Device("mock://dmm").OpenDmmAsync();
var volts = await dmm.MeasureVoltageDcAsync();
Console.WriteLine($"{volts} V");

dotnet run --project examples/MockFixtureCiAsync

VISA async honesty

VisaAsyncTransport wraps sync VisaTransport in SyncAsAsyncTransport:

• WriteAsync / ReadAsync run blocking VISA I/O on the thread pool.
• CancellationToken cancels queued bridge work before it starts; it does not cancel an in-flight native VISA call the way true APM would.
• This is intentional until vendor APM proves reliable across Keysight and NI on Windows and Linux.

Do not advertise “true async VISA I/O” for the C# package yet. Rust already has true async via visa-rs InstrumentTokioAdapter — see Rust async.

Hardware

using InstrumentComponents.Visa;

var catalog = await VisaDiscovery.Create().ScanAsync();
var dmm = await catalog
    .Device(catalog.DevicesByKind(InstrumentComponents.Kind.InstrumentKind.Dmm)[0].Address.Raw)
    .OpenDmmAsync();
var volts = await dmm.MeasureVoltageDcAsync();

Related

• C# VISA — packages and platform notes
• Agent spike notes: repo docs/visa-async-csharp.md

A running native call owns its read/write buffer until it finishes under the VISA timeout. Its task remains pending until then. Complete session queries serialize the write/read pair so concurrent callers cannot exchange replies. Dispose waits for an active call before closing the native session.