65 lines
3.0 KiB
C#
65 lines
3.0 KiB
C#
using Shouldly;
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using Xunit;
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namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests.DL205;
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/// <summary>
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/// Verifies DL205/DL260 CDAB word ordering for 32-bit floats against the
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/// <c>dl205.json</c> pymodbus profile. DirectLOGIC stores IEEE-754 singles with the low
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/// word at the lower register address (CDAB) rather than the high word (ABCD). Reading
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/// <c>HR[1056..1057]</c> with <see cref="ModbusByteOrder.BigEndian"/> produces a tiny
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/// denormal (~5.74e-41) instead of the intended 1.5f — a silent "value is 0" bug in the
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/// field unless the caller opts into <see cref="ModbusByteOrder.WordSwap"/>.
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/// </summary>
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[Collection(ModbusSimulatorCollection.Name)]
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[Trait("Category", "Integration")]
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[Trait("Device", "DL205")]
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public sealed class DL205FloatCdabQuirkTests(ModbusSimulatorFixture sim)
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{
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[Fact]
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public async Task DL205_Float32_CDAB_decodes_1_5f_from_HR1056()
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{
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if (sim.SkipReason is not null) Assert.Skip(sim.SkipReason);
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if (!string.Equals(Environment.GetEnvironmentVariable("MODBUS_SIM_PROFILE"), "dl205",
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StringComparison.OrdinalIgnoreCase))
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{
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Assert.Skip("MODBUS_SIM_PROFILE != dl205 — skipping (standard profile does not seed HR[1056..1057]).");
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}
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var options = new ModbusDriverOptions
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{
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Host = sim.Host,
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Port = sim.Port,
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UnitId = 1,
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Timeout = TimeSpan.FromSeconds(2),
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Tags =
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[
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new ModbusTagDefinition("DL205_Float_CDAB",
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ModbusRegion.HoldingRegisters, Address: 1056,
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DataType: ModbusDataType.Float32, Writable: false,
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ByteOrder: ModbusByteOrder.WordSwap),
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// Control: same address, BigEndian — proves the default decode produces garbage.
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new ModbusTagDefinition("DL205_Float_ABCD",
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ModbusRegion.HoldingRegisters, Address: 1056,
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DataType: ModbusDataType.Float32, Writable: false,
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ByteOrder: ModbusByteOrder.BigEndian),
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],
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Probe = new ModbusProbeOptions { Enabled = false },
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};
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await using var driver = new ModbusDriver(options, driverInstanceId: "dl205-cdab");
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await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);
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var results = await driver.ReadAsync(["DL205_Float_CDAB", "DL205_Float_ABCD"],
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TestContext.Current.CancellationToken);
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results[0].StatusCode.ShouldBe(0u);
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results[0].Value.ShouldBe(1.5f, "DL205 Float32 with WordSwap (CDAB) must decode HR[1056..1057] as 1.5f");
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// The BigEndian read of the same wire bytes should differ — not asserting the exact
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// denormal value (that couples the test to IEEE-754 bit math) but the two decodes MUST
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// disagree, otherwise the word-order flag is a no-op.
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results[1].StatusCode.ShouldBe(0u);
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results[1].Value.ShouldNotBe(1.5f);
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}
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}
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