P1 仪表 CRC16 校验和

Question

我正在尝试为 P1 计量消息的 CRC16 校验和编写单元测试（并且很难做到正确...）。

我有的是：

P1 仪表消息
剥离它以便我根据规范获得正确的部分（见下文）
转成字节数组（ASCII编码）
计算 CRC16 校验和
将其与应有的校验和进行比较

考虑到我 post 在 SO 上提出了一个问题，结果不正确...

请耐心等待，我将在下面分享我的内容：

P1 消息

    private static readonly string telegramText =
        "/KFM5KAIFA-METER\n" +
        "\n" +
        "1-3:0.2.8(42)\n" +
        "0-0:1.0.0(170124213128W)\n" +
        "0-0:96.1.1(4530303236303030303234343934333135)\n" +
        "1-0:1.8.1(000306.946*kWh)\n" +
        "1-0:1.8.2(000210.088*kWh)\n" +
        "1-0:2.8.1(000000.000*kWh)\n" +
        "1-0:2.8.2(000000.000*kWh)\n" +
        "0-0:96.14.0(0001)\n" +
        "1-0:1.7.0(02.793*kW)\n" +
        "1-0:2.7.0(00.000*kW)\n" +
        "0-0:96.7.21(00001)\n" +
        "0-0:96.7.9(00001)\n" +
        "1-0:99.97.0(1)(0-0:96.7.19)(000101000006W)(2147483647*s)\n" +
        "1-0:32.32.0(00000)\n" +
        "1-0:52.32.0(00000)\n" +
        "1-0:72.32.0(00000)\n" +
        "1-0:32.36.0(00000)\n" +
        "1-0:52.36.0(00000)\n" +
        "1-0:72.36.0(00000)\n" +
        "0-0:96.13.1()\n" +
        "0-0:96.13.0()\n" +
        "1-0:31.7.0(003*A)\n" +
        "1-0:51.7.0(005*A)\n" +
        "1-0:71.7.0(005*A)\n" +
        "1-0:21.7.0(00.503*kW)\n" +
        "1-0:41.7.0(01.100*kW)\n" +
        "1-0:61.7.0(01.190*kW)\n" +
        "1-0:22.7.0(00.000*kW)\n" +
        "1-0:42.7.0(00.000*kW)\n" +
        "1-0:62.7.0(00.000*kW)\n" +
        "0-1:24.1.0(003)\n" +
        "0-1:96.1.0(4730303331303033333738373931363136)\n" +
        "0-1:24.2.1(170124210000W)(00671.790*m3)\n" +
        "!29ED\n";

规范

可以找到来源here

CRC is a CRC16 value calculated over the preceding characters in the data message (from “/” to “!” using the polynomial: x16 + x15 + x2 + 1).

CRC16 uses no XOR in, no XOR out and is computed with least significant bit first. The value is represented as 4 hexadecimal characters (MSB first).

获取字节，进行CRC校验

读取的消息是上面的P1消息，但是从'/'到'!' （包括“/”和“！”），如上述规范所述。

var bytes = Encoding.ASCII.GetBytes(_readMessage);
var computeChecksum = new Crc16().ComputeChecksum(bytes);

最后，CRC码

可以找到来源here

public class Crc16
{
    const ushort polynomial = 0xA001;
    ushort[] table = new ushort[256];

    public ushort ComputeChecksum(byte[] bytes)
    {
        ushort crc = 0;
        for (int i = 0; i < bytes.Length; ++i)
        {
            byte index = (byte)(crc ^ bytes[i]);
            crc = (ushort)((crc >> 8) ^ table[index]);
        }
        return crc;
    }

    public byte[] ComputeChecksumBytes(byte[] bytes)
    {
        ushort crc = ComputeChecksum(bytes);
        return BitConverter.GetBytes(crc);
    }

    public Crc16()
    {
        ushort value;
        ushort temp;
        for (ushort i = 0; i < table.Length; ++i)
        {
            value = 0;
            temp = i;
            for (byte j = 0; j < 8; ++j)
            {
                if (((value ^ temp) & 0x0001) != 0)
                {
                    value = (ushort)((value >> 1) ^ polynomial);
                }
                else
                {
                    value >>= 1;
                }
                temp >>= 1;
            }
            table[i] = value;
        }
    }
}

不幸的结果

P1报文的校验和应该是：0x29ED，可惜我算出来的是0x6500

有人能指出我正确的方向吗？

更新

@Mark Adler，我解决了你发现的问题，但我仍然计算出错误的校验和。下面我把不相关的部分都去掉了，你能不能再看看？如果您愿意，可以简单地复制粘贴下面的代码。或者，post 返回计算正确校验和的代码。

提前致谢！

class Program
{
    private static readonly string telegramText =
        "/KFM5KAIFA-METER\r\n" +
        "\r\n" +
        "1-3:0.2.8(42)\r\n" +
        "0-0:1.0.0(170124213128W)\r\n" +
        "0-0:96.1.1(4530303236303030303234343934333135)\r\n" +
        "1-0:1.8.1(000306.946*kWh)\r\n" +
        "1-0:1.8.2(000210.088*kWh)\r\n" +
        "1-0:2.8.1(000000.000*kWh)\r\n" +
        "1-0:2.8.2(000000.000*kWh)\r\n" +
        "0-0:96.14.0(0001)\r\n" +
        "1-0:1.7.0(02.793*kW)\r\n" +
        "1-0:2.7.0(00.000*kW)\r\n" +
        "0-0:96.7.21(00001)\r\n" +
        "0-0:96.7.9(00001)\r\n" +
        "1-0:99.97.0(1)(0-0:96.7.19)(000101000006W)(2147483647*s)\r\n" +
        "1-0:32.32.0(00000)\r\n" +
        "1-0:52.32.0(00000)\r\n" +
        "1-0:72.32.0(00000)\r\n" +
        "1-0:32.36.0(00000)\r\n" +
        "1-0:52.36.0(00000)\r\n" +
        "1-0:72.36.0(00000)\r\n" +
        "0-0:96.13.1()\r\n" +
        "0-0:96.13.0()\r\n" +
        "1-0:31.7.0(003*A)\r\n" +
        "1-0:51.7.0(005*A)\r\n" +
        "1-0:71.7.0(005*A)\r\n" +
        "1-0:21.7.0(00.503*kW)\r\n" +
        "1-0:41.7.0(01.100*kW)\r\n" +
        "1-0:61.7.0(01.190*kW)\r\n" +
        "1-0:22.7.0(00.000*kW)\r\n" +
        "1-0:42.7.0(00.000*kW)\r\n" +
        "1-0:62.7.0(00.000*kW)\r\n" +
        "0-1:24.1.0(003)\r\n" +
        "0-1:96.1.0(4730303331303033333738373931363136)\r\n" +
        "0-1:24.2.1(170124210000W)(00671.790*m3)\r\n" +
        "!";

    static void Main(string[] args)
    {
        var bytes = Encoding.ASCII.GetBytes(telegramText);
        var computeChecksum = new Crc16().ComputeChecksum(bytes);
    }
}

public class Crc16
{
    const ushort polynomial = 0x8005;
    ushort[] table = new ushort[256];

    public ushort ComputeChecksum(byte[] bytes)
    {
        ushort crc = 0;
        for (int i = 0; i < bytes.Length; ++i)
        {
            byte index = (byte)(crc ^ bytes[i]);
            crc = (ushort)((crc >> 8) ^ table[index]);
        }
        return crc;
    }

    public byte[] ComputeChecksumBytes(byte[] bytes)
    {
        ushort crc = ComputeChecksum(bytes);
        return BitConverter.GetBytes(crc);
    }

    public Crc16()
    {
        ushort value;
        ushort temp;
        for (ushort i = 0; i < table.Length; ++i)
        {
            value = 0;
            temp = i;
            for (byte j = 0; j < 8; ++j)
            {
                if (((value ^ temp) & 0x0001) != 0)
                {
                    value = (ushort)((value >> 1) ^ polynomial);
                }
                else
                {
                    value >>= 1;
                }
                temp >>= 1;
            }
            table[i] = value;
        }
    }
}

Answer 1

CRC 码看起来没问题。问题是它期待回车 return-line 提要，而不仅仅是换行。如果您在每个 \n 之前加上 \r，那么您会得到 0x29ed 用于从 / 到 ! 的字节的 CRC，包括在内。

P1 仪表 CRC16 校验和

P1 Meter CRC16 checksum

c#

crc

crc16

smartmeter

P1 消息

规范

获取字节，进行CRC校验

最后，CRC码

不幸的结果

更新