您如何計(jì)算傳入字節(jié)的校驗(yàn)和以查看它是否是有效數(shù)據(jù)包？目前我正在讀取字節(jié)并對(duì)它們進(jìn)行解碼并接收信息，但在我這樣做之前我希望能夠根據(jù)校驗(yàn)和驗(yàn)證它以確保我沒有收到任何無效/損壞的數(shù)據(jù)包。這是我目前擁有的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 serclass 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] = valueif __name__ == "__main__": print("BATTERY MONITOR") bmv700 = VictronBmv700("COM17", 19200) bmv700.getBMVInfo()
2 回答
千萬里不及你
TA貢獻(xiàn)1784條經(jīng)驗(yàn) 獲得超9個(gè)贊
發(fā)帖者似乎正在嘗試從 BMV700 電池監(jiān)視器讀取數(shù)據(jù)。閱讀此處的論文，我們看到它使用文本協(xié)議通過串行接口進(jìn)行通信：
2 文本協(xié)議
當(dāng)沒有 VE.Direct 查詢發(fā)送到設(shè)備時(shí)，充電器會(huì)定期將人類可讀 (TEXT) 數(shù)據(jù)發(fā)送到串行端口。有關(guān)內(nèi)容和信息可用性的詳細(xì)說明，請(qǐng)參閱“VE.Direct Protocol”文檔
摘自 HEX 協(xié)議 (BMV-7xx-HEX-Protocol-public.pdf)
查看 TEXT 協(xié)議的規(guī)范 (VE.Direct-Protocol-3.28.pdf)，我們發(fā)現(xiàn)：
消息格式
該設(shè)備以 1 秒的間隔傳輸數(shù)據(jù)塊。每個(gè)字段都使用以下格式發(fā)送：
<Newline><Field-Label><Tab><Field-Value>
標(biāo)識(shí)符定義如下：
+---------------+--------------------------------------------------------------------------------------+
| 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. |
+---------------+--------------------------------------------------------------------------------------+
這對(duì)應(yīng)于您正在打印的數(shù)據(jù)，但有一個(gè)例外：該行以 開頭，\r\b但不以它們結(jié)尾。
然后，該文件提供了有關(guān)校驗(yàn)和的詳細(xì)信息：
數(shù)據(jù)的完整性
統(tǒng)計(jì)數(shù)據(jù)分組為塊，并附加了校驗(yàn)和。塊中的最后一個(gè)字段將始終是“校驗(yàn)和”。該值是一個(gè)字節(jié)，不一定是可打印的 ASCII 字符。如果沒有傳輸錯(cuò)誤，塊中所有字節(jié)的模 256 和將等于 0。發(fā)送包含不同字段的多個(gè)塊。
因此，在您作為輸出發(fā)布的摘錄中，您有兩個(gè)完整的塊和一個(gè)不完整的塊，因?yàn)樽詈笠粋€(gè)塊缺少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')
請(qǐng)注意，我\r\n在開頭添加了，并從塊的末尾刪除了它們，這樣最后一個(gè)字節(jié)就是塊的校驗(yàn)和。
現(xiàn)在，我們可以計(jì)算塊的校驗(yàn)和：
>>> sum(block) % 256
213
這應(yīng)該是零。因此，可能存在一些傳輸問題，或者他們計(jì)算校驗(yàn)和的方式可能與他們?cè)谖臋n中所說的不同。
新數(shù)據(jù)后編輯。
這是我用來檢查您發(fā)布的所有塊的代碼：
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，對(duì)于第一次運(yùn)行，您總是得到等于檢索到的計(jì)算值 + 1，但在第二次運(yùn)行中卻沒有。因此，可能存在一些傳輸問題。
慕桂英546537
TA貢獻(xiàn)1848條經(jīng)驗(yàn) 獲得超10個(gè)贊
下面的代碼比較了兩個(gè)文件，在這種情況下，正如提問者提到的校驗(yàn)和：
bmvdata = batteryConnect(self.port,self.baudrate)
bmvdata.flushInput()
print(bmvdata.readline())
它是在hashlib的幫助下完成的
import hashlib
#File 1 = checksum
hasher1 = hashlib.md5()
#afile1 = open('checksum', 'rb')
buf1 = bmvdata.read()
#buf1 = afile1.read()
a = hasher1.update(buf1)
md5_a=(str(hasher1.hexdigest()))
#File 2
hasher2 = hashlib.md5()
afile2 = open('incoming-byte', 'rb')
buf2 = afile2.read()
b = hasher2.update(buf2)
md5_b=(str(hasher2.hexdigest()))
#Compare md5
if(md5_a==md5_b):
print("Yes")
else:
print("No")
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