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python - 如何将字节添加在一起并根据python中的校验和验证它们

问题描述

您如何计算传入字节的校验和以查看它是否是有效数据包？目前我正在读取字节并对其进行解码并接收信息，但在此之前，我希望能够根据校验和对其进行验证，以确保我没有收到任何无效/损坏的数据包。

这是我目前拥有的

def batteryConnect(port, baudrate):
    # establishing a serial connection
    ser = serial.Serial(port=port, baudrate= baudrate, bytesize=serial.EIGHTBITS, parity=serial.PARITY_NONE,timeout=3)
    return ser

class VictronBmv700:

    def __init__(self,port,baudrate):
        self.port = port
        self.baudrate = baudrate
        self.parameterDict = dict.fromkeys(["PID","V","I","P","CE","SOC","TTG","Alarm","Relay","AR","BMV","FW","H1","H2","H3",
                                  "H4","H5","H6","H7","H8","H9","H10","H11","H12","H17","H18"])


    def getBMVInfo(self):

        bmvdata = batteryConnect(self.port,self.baudrate)

        #getting the data
        bmvdata.flushInput()

        #getting the message then splitting the key, value pairs
        while True:
            print(bmvdata.readline())

            message = bmvdata.readline().decode(encoding='utf-8',errors='ignore')

            #splitting on tabs
            message_parts = message.split('\t')

            if len(message_parts) > 1:
                key = message_parts[0]
                value = message_parts[1].rstrip()  #stripping \r\n after the value


                #updating deictionary based on keys and their values.
                self.parameterDict[key] = value

if __name__ == "__main__":
    print("BATTERY MONITOR")
    bmv700 = VictronBmv700("COM17", 19200)
    bmv700.getBMVInfo()

开始输出以下内容（来自 print(bmvdata.readline()) ）

b'\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd7\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd6\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'

如何根据校验和检查传入字节，然后在验证后继续解码？

编辑 有时我会得到不同的校验和值，如下所示。这是我运行代码的另外两次。

b'\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd0\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd7\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd0\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd8\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd8\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd8\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd0\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd0\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd8\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd8\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd8\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd8\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd8\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd8\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd0\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd0\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd0\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd0\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'
b'PID\t0x203\r\n'
b'I\t0\r\n'
b'CE\t0\r\n'
b'TTG\t-1\r\n'
b'Relay\tOFF\r\n'
b'BMV\t700\r\n'
b'Checksum\t\xd0\r\n'
b'H2\t0\r\n'
b'H4\t0\r\n'
b'H6\t-9001\r\n'
b'H8\t28403\r\n'
b'H10\t0\r\n'
b'H12\t0\r\n'
b'H18\t87\r\n'

第二轮

b'\r\n'
b'V\t25548\r\n'
b'P\t0\r\n'
b'SOC\t1000\r\n'
b'Alarm\tOFF\r\n'
b'AR\t0\r\n'
b'FW\t0310\r\n'
b'H1\t-6254\r\n'
b'H3\t0\r\n'
b'H5\t0\r\n'
b'H7\t-10\r\n'
b'H9\t0\r\n'
b'H11\t0\r\n'
b'H17\t20\r\n'
b'Checksum\tT\r\n'
b'V\t25549\r\n'
b'P\t0\r\n'
b'SOC\t1000\r\n'
b'Alarm\tOFF\r\n'
b'AR\t0\r\n'
b'FW\t0310\r\n'
b'H1\t-6254\r\n'
b'H3\t0\r\n'
b'H5\t0\r\n'
b'H7\t-10\r\n'
b'H9\t0\r\n'
b'H11\t0\r\n'
b'H17\t20\r\n'
b'Checksum\tT\r\n'
b'V\t25548\r\n'
b'P\t0\r\n'
b'SOC\t1000\r\n'
b'Alarm\tOFF\r\n'
b'AR\t0\r\n'
b'FW\t0310\r\n'
b'H1\t-6254\r\n'
b'H3\t0\r\n'
b'H5\t0\r\n'
b'H7\t-10\r\n'
b'H9\t0\r\n'
b'H11\t0\r\n'
b'H17\t20\r\n'
b'Checksum\tT\r\n'
b'V\t25548\r\n'
b'P\t0\r\n'
b'SOC\t1000\r\n'
b'Alarm\tOFF\r\n'
b'AR\t0\r\n'
b'FW\t0310\r\n'
b'H1\t-6254\r\n'
b'H3\t0\r\n'
b'H5\t0\r\n'
b'H7\t-10\r\n'
b'H9\t0\r\n'
b'H11\t0\r\n'
b'H17\t20\r\n'
b'Checksum\tT\r\n'
b'V\t25549\r\n'
b'P\t0\r\n'
b'SOC\t1000\r\n'
b'Alarm\tOFF\r\n'
b'AR\t0\r\n'
b'FW\t0310\r\n'
b'H1\t-6254\r\n'
b'H3\t0\r\n'
b'H5\t0\r\n'
b'H7\t-10\r\n'
b'H9\t0\r\n'
b'H11\t0\r\n'
b'H17\t20\r\n'
b'Checksum\tT\r\n'
b'V\t25548\r\n'
b'P\t0\r\n'
b'SOC\t1000\r\n'
b'Alarm\tOFF\r\n'
b'AR\t0\r\n'
b'FW\t0310\r\n'
b'H1\t-6254\r\n'
b'H3\t0\r\n'
b'H5\t0\r\n'
b'H7\t-10\r\n'
b'H9\t0\r\n'
b'H11\t0\r\n'
b'H17\t20\r\n'
b'Checksum\tT\r\n'
b'V\t25548\r\n'
b'P\t0\r\n'
b'SOC\t1000\r\n'
b'Alarm\tOFF\r\n'
b'AR\t0\r\n'
b'FW\t0310\r\n'
b'H1\t-6254\r\n'
b'H3\t0\r\n'
b'H5\t0\r\n'
b'H7\t-10\r\n'
b'H9\t0\r\n'
b'H11\t0\r\n'
b'H17\t20\r\n'
b'Checksum\tT\r\n'
b'V\t25548\r\n'
b'P\t0\r\n'
b'SOC\t1000\r\n'
b'Alarm\tOFF\r\n'
b'AR\t0\r\n'
b'FW\t0310\r\n'
b'H1\t-6254\r\n'
b'H3\t0\r\n'
b'H5\t0\r\n'
b'H7\t-10\r\n'
b'H9\t0\r\n'
b'H11\t0\r\n'
b'H17\t20\r\n'
b'Checksum\tT\r\n'
b'V\t25548\r\n'
b'P\t0\r\n'
b'SOC\t1000\r\n'
b'Alarm\tOFF\r\n'
b'AR\t0\r\n'
b'FW\t0310\r\n'

编辑 运行以下代码

current_block = []
# it's unfortunate that lines start with `\r\n` rather than end with it
# we will read the first empty line separatey, and then include these 
# 2 characters in the last line that is read
message = bmvdata.readline()
while True:
    # Note that we cannot decode yet, since the Checksum value may not be a valid utf8 character
    message = bmvdata.readline()

    # we save the message in the current block before any preprocessing
    current_block.append(message)

    #splitting on tabs (as bytes !!)
    message_parts = message.split(b'\t')

    if len(message_parts) > 1:
        key = message_parts[0].decode('utf8')  # here it is safe to decode the key
        value = message_parts[1].rstrip()  #stripping \r\n after the value

    if key == 'Checksum':
        block_chars = b''.join(current_block)
        checksum = sum(block_chars) % 256
        print('Retrieved  checksum', value[-1])
        print('Calculated checksum', checksum)
        print('----')

        # reset the block
        current_block = []

输出

Retrieved checksum 84
Calculated checksum 0
-------
Retrieved checksum 219
Calculated checksum 0
-------
Retrieved checksum 84
Calculated checksum 0
-------
Retrieved checksum 220
Calculated checksum 0
-------
Retrieved checksum 84
Calculated checksum 0
-------
Retrieved checksum 219
Calculated checksum 0
-------
Retrieved checksum 84
Calculated checksum 0
-------
Retrieved checksum 219
Calculated checksum 0
-------
Retrieved checksum 84
Calculated checksum 0
-------
Retrieved checksum 220
Calculated checksum 0
-------
Retrieved checksum 84
Calculated checksum 0
-------
Retrieved checksum 220
Calculated checksum 0
-------
Retrieved checksum 84
Calculated checksum 0
-------
Retrieved checksum 220
Calculated checksum 0
-------
Retrieved checksum 84
Calculated checksum 0
-------
Retrieved checksum 219
Calculated checksum 0
-------
Retrieved checksum 84
Calculated checksum 0
-------

标签： pythonpython-3.xpyserialchecksum

解决方案

看来张贴者正试图从 BMV700 电池监视器读取数据。阅读这里的论文，我们看到它使用文本协议通过串行接口进行通信：

2 文本协议

当没有向设备发送 VE.Direct 查询时，充电器会定期向串行端口发送人类可读 (TEXT) 数据。有关信息内容和可用性的详细说明，请参阅“VE.Direct 协议”文档

HEX 协议摘录 (BMV-7xx-HEX-Protocol-public.pdf)

查看 TEXT 协议的规范（VE.Direct-Protocol-3.28.pdf），我们发现：

消息格式

设备以 1 秒的间隔传输数据块。每个字段都使用以下格式发送：

<Newline><Field-Label><Tab><Field-Value>

标识符定义如下：

+---------------+--------------------------------------------------------------------------------------+
| Identifier    | Meaning                                                                              |
+===============+======================================================================================+
| <Newline>     | A carriage return followed by a line feed (0x0D, 0x0A).                              |
+---------------+--------------------------------------------------------------------------------------+
| <Field-Label> | An arbitrary length label that identifies the field.                                 |
|               | Where applicable, this will be the same as the label that is used on the LCD.        |
+---------------+--------------------------------------------------------------------------------------+
| <Tab>         | A horizontal tab (0x09).                                                             |
+---------------+--------------------------------------------------------------------------------------+
| <Field-Value> | The ASCII formatted value of this field.                                             |
|               | The number of characters transmitted depends on the magnitude and sign of the value. |
+---------------+--------------------------------------------------------------------------------------+

这与您正在打印的数据相对应，但有一个例外：该行以 开头，\r\b但不以它们结尾。

然后，该文件提供了有关校验和的详细信息：

数据的完整性

统计信息按块分组，并附加校验和。块中的最后一个字段将始终是“校验和”。该值是单个字节，不一定是可打印的 ASCII 字符。如果没有传输错误，则块中所有字节的模 256 总和将等于 0。发送包含不同字段的多个块。

因此，在您作为输出发布的摘录中，您有两个完整的块和一个不完整的块，因为最后一个块缺少Checksum.

block = (b'\r\nH2\t0\r\n'
    b'H4\t0\r\n'
    b'H6\t-9001\r\n'
    b'H8\t28403\r\n'
    b'H10\t0\r\n'
    b'H12\t0\r\n'
    b'H18\t87\r\n'
    b'PID\t0x203\r\n'
    b'I\t0\r\n'
    b'CE\t0\r\n'
    b'TTG\t-1\r\n'
    b'Relay\tOFF\r\n'
    b'BMV\t700\r\n'
    b'Checksum\t\xd6')

请注意，我\r\n在开头添加了 ，并从块的末尾删除了它们，这样最后一个字节就是块的校验和。

现在，我们可以计算块的校验和：

>>> sum(block) % 256
213

这应该是零。因此，可能存在一些传输问题，或者他们计算校验和的方式可能与他们在文档中所说的不同。

新数据后编辑。

这是我用来检查您发布的所有块的代码：

current_block = []
# it's unfortunate that lines start with `\r\n` rather than end with it
# we will read the first empty line separatey, and then include these 
# 2 characters in the last line that is read
message = bmvdata.readline()
while True:
    # Note that we cannot decode yet, since the Checksum value may not be a valid utf8 character
    message = bmvdata.readline()

    # we save the message in the current block before any preprocessing
    current_block.append(message)

    #splitting on tabs (as bytes !!)
    message_parts = message.split(b'\t')

    if len(message_parts) > 1:
        key = message_parts[0].decode('utf8')  # here it is safe to decode the key
        value = message_parts[1].rstrip()  #stripping \r\n after the value

    if key == 'Checksum':
        block_chars = b''.join(current_block)
        checksum = sum(block_chars) % 256
        print('Retrieved  checksum', value[-1])
        print('Calculated checksum', checksum)
        print('----')

        # reset the block
        current_block = []

奇怪的是，对于第一次运行，您总是得到等于检索 + 1 的计算值，但在第二次运行中却不是。因此，可能存在一些传输问题。

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