55 lines
1.7 KiB
C#
55 lines
1.7 KiB
C#
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namespace SSPCTester.Devices.Protocol;
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public static class ModbusRtuProtocol
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{
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public static ushort ComputeCrc(ReadOnlySpan<byte> data)
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{
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ushort crc = 0xFFFF;
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foreach (byte value in data)
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{
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crc ^= value;
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for (int i = 0; i < 8; i++)
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crc = (ushort)((crc & 1) != 0 ? (crc >> 1) ^ 0xA001 : crc >> 1);
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}
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return crc;
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}
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public static byte[] BuildRequest(byte slave, byte function, ushort address, ushort valueOrCount)
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{
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var frame = new byte[8];
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frame[0] = slave;
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frame[1] = function;
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frame[2] = (byte)(address >> 8);
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frame[3] = (byte)address;
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frame[4] = (byte)(valueOrCount >> 8);
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frame[5] = (byte)valueOrCount;
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ushort crc = ComputeCrc(frame.AsSpan(0, 6));
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frame[6] = (byte)crc;
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frame[7] = (byte)(crc >> 8);
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return frame;
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}
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public static void ValidateCrc(ReadOnlySpan<byte> frame)
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{
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if (frame.Length < 5) throw new InvalidDataException("Modbus 响应长度不足。");
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ushort expected = ComputeCrc(frame[..^2]);
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ushort actual = (ushort)(frame[^2] | frame[^1] << 8);
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if (expected != actual)
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throw new InvalidDataException($"Modbus CRC 错误，期望 {expected:X4}，实际 {actual:X4}。");
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}
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}
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public static class ModbusValueConverter
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{
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public static double ConvertRaw(ushort rawBits, bool signed, string formula, double range)
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{
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double raw = signed ? unchecked((short)rawBits) : rawBits;
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return formula switch
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{
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"A" => raw / 10000.0 * range,
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"B" => raw / range,
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_ => throw new InvalidDataException($"不支持换算公式 {formula}")
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};
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}
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}
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