OpenTAP pack (C#)¶

InstrumentComponents.OpenTap is an OpenTAP plugin with all eight SCPI instrument types and explicit typed TestStep classes. The host injects an already-open message session, or registers an IOpenTapScpiIoProvider. The pack never opens a vendor VISA resource manager.

Install¶

NuGet publishing is deferred. From this repo:

dotnet add reference path/to/InstrumentComponents.OpenTap.csproj

The pack references OpenTAP 9.32 and InstrumentComponents only — not InstrumentComponents.Visa. Hosts that need TUI-without-host can reference the optional companion InstrumentComponents.OpenTap.Visa.

Session injection¶

Call AttachSession (or the IScpiIo constructor) before Instrument.Open:

using InstrumentComponents.OpenTap;
using InstrumentComponents.Scpi;

var io = new DelegateScpiIo(write, query); // wrap the host's Write/Query
var dmm = new DmmInstrument { VisaAddress = "TCPIP0::192.0.2.10::inst0::INSTR" };
dmm.AttachSession(io);
dmm.Open();

VisaAddress is pack-safe discovery metadata. Without an attached session and without a provider, Open() throws and does not call IVI.

Optional process-wide provider (for TUI-without-host; HardwareTest should keep injecting):

OpenTapScpiIo.Provider = new MyHostScpiIoProvider(); // IOpenTapScpiIoProvider
var dmm = new DmmInstrument { VisaAddress = "TCPIP0::192.0.2.10::inst0::INSTR" };
dmm.Open(); // provider.Open(VisaAddress, timeout) then IDN

AttachSession / the IScpiIo constructor still win over the provider. Close disposes provider-created I/O and leaves host-injected I/O alone.

Optional VISA companion¶

InstrumentComponents.OpenTap.Visa is not part of the .TapPackage. Reference it from a host that already has a vendor VISA runtime:

using InstrumentComponents.OpenTap;
using InstrumentComponents.OpenTap.Visa;

OpenTapVisa.Register(); // no-op when a host already set OpenTapScpiIo.Provider
var dmm = new DmmInstrument { VisaAddress = "TCPIP0::192.0.2.10::inst0::INSTR" };
dmm.Open();

HardwareTest should keep injecting IScpiIo. The companion exists for TUI-without-host. Self-hosted smoke uses INSTRUMENT_RESOURCE and Category=Hardware (same gate as InstrumentComponents.Visa).

Plan-author steps¶

Steps are explicit types (stable TapPlan names), not a generic "call method" broker.

Kind	Examples
Utility	`IdentityQueryStep`, `SafeShutdownStep`
Composite	`PsuConfigureOutputStep`, `FgenConfigureOutputStep`, `ScopeCaptureTraceStep`
Generated invoke	`DmmMeasureVoltageAcStep`, `PsuSetVoltageStep`, `ScopeRunStep`, …

Generated wrappers come from spec/opentap-operations.json. Do not rename stepTypeName values — they are TapPlan contract.

Scalar measure steps inherit optional inclusive LimitLow / LimitHigh (unset = no fail).

Phase I results¶

Table	Columns
`Sample`	Channel, Index, Value
`Scalar`	Name, Value, Unit, LimitLow, LimitHigh
`Identity`	Idn, DutSerial

Mock plan (no VISA)¶

using InstrumentComponents.OpenTap;
using InstrumentComponents.Scpi;
using OpenTap;

var io = new DelegateScpiIo(
    write: _ => { },
    query: command => command.Trim().Equals("*IDN?", StringComparison.OrdinalIgnoreCase)
        ? "Acme,DMM1,SN,1.0"
        : "1.25");

var dmm = new DmmInstrument(io) { Name = "Bench DMM", VisaAddress = "mock://dmm" };
var plan = new TestPlan();
plan.ChildTestSteps.Add(new IdentityQueryStep { Instrument = dmm });
plan.ChildTestSteps.Add(new DmmMeasureVoltageAcStep { Instrument = dmm, LimitLow = 1.0, LimitHigh = 2.0 });
plan.Execute();

dotnet run --project dotnet/examples/OpenTapMockPlan

TapPackage¶

The plugin library stays net8.0. Creating a .TapPackage needs a net9 runtime for the OpenTAP tap CLI:

dotnet build dotnet/src/InstrumentComponents.OpenTap/InstrumentComponents.OpenTap.csproj -c Release -p:CreateOpenTapPackage=true

That emits InstrumentComponents.OpenTap.0.1.0.TapPackage (plugin DLL + InstrumentComponents.dll, no VISA). Install with tap package install.

HardwareTest¶

The bench shell owns broker, gate, and operator UI. This pack is the plugin that shell consumes. Contributor layering notes: docs/opentap-consumer.md in the repo.

Acquisition units and PSU shutdown¶

DMM READ/FETCH publish the unit of the last function configured through the typed DMM view: volts, amperes, or ohms. Before configuration, and after reset, the unit is empty because the library has no confirmed function. Configure the function before acquisition if result units are required.

For a PSU using the generic dialect, set Output Channels to the physical channel count before Safe Shutdown. Known vendor dialects provide their count. Shutdown attempts every configured channel and every output enabled through any view of the session, even when an individual OFF command fails. If the physical count is unknown, known outputs are disabled and shutdown reports an unsupported operation instead of claiming that every output is off. Bench verification of every output is still required before relying on this with a real supply.

Nonfinite scalar readings and sample/trace values fail the plan. Numeric settings and configured limits must be finite; absent limits remain optional. N6705 remote-sense ON/OFF is explicitly unsupported until its INT/EXT command has vendor coverage.