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Phase 3 PR 46 -- DL205 BCD decoder (binary-coded-decimal numeric encoding). Adds ModbusDataType.Bcd16 and Bcd32 to the driver. Bcd16 is 1 register wide, Bcd32 is 2 registers wide; Bcd32 respects ModbusByteOrder (BigEndian/WordSwap) the same way Int32 does so the CDAB-style families (including DL205/DL260 themselves) can be configured. DecodeRegister uses the new internal DecodeBcd helper: walks each nibble from MSB to LSB, multiplies the running result by 10, adds the nibble as a decimal digit. Explicitly rejects nibbles > 9 with InvalidDataException -- hardware sometimes produces garbage during write-in-progress transitions and silently returning wrong numeric values would quietly corrupt the caller's data. EncodeRegister's new EncodeBcd inverts the operation (mod/div by 10 nibble-by-nibble) with an up-front overflow check against 10^nibbles-1. Why this matters for DL205/DL260: AutomationDirect DirectLOGIC uses BCD as the default numeric encoding for timers, counters, and operator-display numerics (not binary). A plain Int16 read of register 0x1234 returns 4660; the BCD path returns 1234. The two differ enough that silently defaulting to Int16 would give wildly wrong HMI values -- the caller must opt in to Bcd16/Bcd32 per tag. Unit tests: DecodeBcd (theory: 0,1,9,10,1234,9999), DecodeBcd_rejects_nibbles_above_nine, EncodeBcd (theory), Bcd16_decodes_DL205_register_1234_as_decimal_1234 (control: same bytes as Int16 decode to 4660), Bcd16_encode_round_trips_with_decode, Bcd16_encode_rejects_out_of_range_values, Bcd32_decodes_8_digits_big_endian, Bcd32_word_swap_handles_CDAB_layout, Bcd32_encode_round_trips_with_decode, Bcd_RegisterCount_matches_underlying_width. 66/66 Modbus.Tests pass. Integration test: DL205BcdQuirkTests.DL205_BCD16_decodes_HR1072_as_decimal_1234 against dl205.json pymodbus profile (HR[1072]=0x1234). Asserts Bcd16 decode=1234 AND Int16 decode=0x1234 on the same wire bytes to prove the paths are distinct. 3/3 DL205 integration tests pass with MODBUS_SIM_PROFILE=dl205.

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This commit is contained in:
Joseph Doherty
2026-04-18 21:46:25 -04:00
parent cd19022d19
commit 8248b126ce
4 changed files with 226 additions and 2 deletions
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93
tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests/ModbusDataTypeTests.cs
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@@ -219,4 +219,97 @@ public sealed class ModbusDataTypeTests
ModbusDriver.DecodeRegister(wire, hi).ShouldBe("He");
ModbusDriver.DecodeRegister(wire, lo).ShouldBe("eH");
}
// --- BCD (binary-coded decimal, DL205/DL260 default numeric encoding) ---
[Theory]
[InlineData(0x0000u, 0u)]
[InlineData(0x0001u, 1u)]
[InlineData(0x0009u, 9u)]
[InlineData(0x0010u, 10u)]
[InlineData(0x1234u, 1234u)]
[InlineData(0x9999u, 9999u)]
public void DecodeBcd_16_bit_decodes_expected_decimal(uint raw, uint expected)
=> ModbusDriver.DecodeBcd(raw, nibbles: 4).ShouldBe(expected);
[Fact]
public void DecodeBcd_rejects_nibbles_above_nine()
{
Should.Throw<InvalidDataException>(() => ModbusDriver.DecodeBcd(0x00A5u, nibbles: 4))
.Message.ShouldContain("Non-BCD nibble");
}
[Theory]
[InlineData(0u, 0x0000u)]
[InlineData(5u, 0x0005u)]
[InlineData(42u, 0x0042u)]
[InlineData(1234u, 0x1234u)]
[InlineData(9999u, 0x9999u)]
public void EncodeBcd_16_bit_encodes_expected_nibbles(uint value, uint expected)
=> ModbusDriver.EncodeBcd(value, nibbles: 4).ShouldBe(expected);
[Fact]
public void Bcd16_decodes_DL205_register_1234_as_decimal_1234()
{
// HR[1072] = 0x1234 on the DL205 profile represents decimal 1234. A plain Int16 decode
// would return 0x04D2 = 4660 — proof the BCD path is different.
var tag = new ModbusTagDefinition("T", ModbusRegion.HoldingRegisters, 0, ModbusDataType.Bcd16);
ModbusDriver.DecodeRegister(new byte[] { 0x12, 0x34 }, tag).ShouldBe(1234);
var int16Tag = tag with { DataType = ModbusDataType.Int16 };
ModbusDriver.DecodeRegister(new byte[] { 0x12, 0x34 }, int16Tag).ShouldBe((short)0x1234);
}
[Fact]
public void Bcd16_encode_round_trips_with_decode()
{
var tag = new ModbusTagDefinition("T", ModbusRegion.HoldingRegisters, 0, ModbusDataType.Bcd16);
var wire = ModbusDriver.EncodeRegister(4321, tag);
wire.ShouldBe(new byte[] { 0x43, 0x21 });
ModbusDriver.DecodeRegister(wire, tag).ShouldBe(4321);
}
[Fact]
public void Bcd16_encode_rejects_out_of_range_values()
{
var tag = new ModbusTagDefinition("T", ModbusRegion.HoldingRegisters, 0, ModbusDataType.Bcd16);
Should.Throw<OverflowException>(() => ModbusDriver.EncodeRegister(10000, tag))
.Message.ShouldContain("4 decimal digits");
}
[Fact]
public void Bcd32_decodes_8_digits_big_endian()
{
// 0x12345678 as BCD = decimal 12_345_678.
var tag = new ModbusTagDefinition("T", ModbusRegion.HoldingRegisters, 0, ModbusDataType.Bcd32);
ModbusDriver.DecodeRegister(new byte[] { 0x12, 0x34, 0x56, 0x78 }, tag).ShouldBe(12_345_678);
}
[Fact]
public void Bcd32_word_swap_handles_CDAB_layout()
{
// PLC stored 12_345_678 with word swap: low-word 0x5678 first, high-word 0x1234 second.
// Wire bytes [0x56, 0x78, 0x12, 0x34] + WordSwap → decode to decimal 12_345_678.
var tag = new ModbusTagDefinition("T", ModbusRegion.HoldingRegisters, 0, ModbusDataType.Bcd32,
ByteOrder: ModbusByteOrder.WordSwap);
ModbusDriver.DecodeRegister(new byte[] { 0x56, 0x78, 0x12, 0x34 }, tag).ShouldBe(12_345_678);
}
[Fact]
public void Bcd32_encode_round_trips_with_decode()
{
var tag = new ModbusTagDefinition("T", ModbusRegion.HoldingRegisters, 0, ModbusDataType.Bcd32);
var wire = ModbusDriver.EncodeRegister(87_654_321u, tag);
wire.ShouldBe(new byte[] { 0x87, 0x65, 0x43, 0x21 });
ModbusDriver.DecodeRegister(wire, tag).ShouldBe(87_654_321);
}
[Fact]
public void Bcd_RegisterCount_matches_underlying_width()
{
var b16 = new ModbusTagDefinition("A", ModbusRegion.HoldingRegisters, 0, ModbusDataType.Bcd16);
var b32 = new ModbusTagDefinition("B", ModbusRegion.HoldingRegisters, 0, ModbusDataType.Bcd32);
ModbusDriver.RegisterCount(b16).ShouldBe((ushort)1);
ModbusDriver.RegisterCount(b32).ShouldBe((ushort)2);
}
}