如何使用Python计算这个CRC？
How to calculate this CRC using Python?
我需要使用 Python 计算此 CRC，以便与 Aurora (ABB) 太阳能逆变器通信。
这是文档：http://www.drhack.it/images/PDF/AuroraCommunicationProtocol_4_2.pdf
在最后一页有计算 CRC 的说明，我需要在 python.
中进行计算
我收到的消息是
MESSAGE_GRID_VOLTAGE = bytes.fromhex("023b010000000000")
结果应该是：
CRC_L = FF
CRC_H = 2C
然后我需要像这样发送带有 CRC 的消息：
MESSAGE_GRID_VOLTAGE = bytes.fromhex("023b010000000000ff2c")
我如何在 python 中做到这一点？谢谢！
这是我试过的代码：
message = "023b010000000000"
BccLo= int ("FF",16)
BccHi= int("FF", 16)
New = int(message, 16)
New = New ^ BccLo
Tmp=New << 4
New=Tmp ^ New
Tmp=New >> 5
BccLo=BccHi
BccHi= New ^ Tmp
Tmp=New << 3
BccLo=BccLo ^ Tmp
Tmp=New >> 4
BccLo=BccLo ^ Tmp
CRC_L = ~BccLo
CRC_H = ~BccHi
您需要将该算法应用于消息的每个字节。有点复杂的是，Aurora PDF 文件中给出的算法假定计算是使用 8 位无符号算法执行的。为了在 Python 中处理这个问题，我们可以使用 0xff 的位掩码。这是该代码的略微优化版本。
def crc_16(msg):
lo = hi = 0xff
mask = 0xff
for new in msg:
new ^= lo
new ^= (new << 4) & mask
tmp = new >> 5
lo = hi
hi = new ^ tmp
lo ^= (new << 3) & mask
lo ^= new >> 4
lo ^= mask
hi ^= mask
return hi << 8 | lo
# Test
msg = bytes.fromhex("023b010000000000")
out = crc_16(msg)
hi, lo = out >> 8, out & 0xff
print('{:04x} = {:02x} {:02x}'.format(out, hi, lo))
输出
2cff = 2c ff
以上代码有效，但有更简单的方法来计算 CRC。如果你需要计算很多 CRC，我们可以使用 table 来加快这个过程。
正如维基百科 Cyclic redundancy check 文章中提到的，CRC 算法通常根据编码为十六进制数的多项式来指定。这是一个使用反向多项式表示的函数。
def crc_16_CCITT(msg):
poly = 0x8408
crc = 0xffff
for byte in msg:
for _ in range(8):
if (byte ^ crc) & 1:
crc = (crc >> 1) ^ poly
else:
crc >>= 1
byte >>= 1
return crc ^ 0xffff
为了加快速度，我们可以计算 table。
def make_crc_table():
poly = 0x8408
table = []
for byte in range(256):
crc = 0
for bit in range(8):
if (byte ^ crc) & 1:
crc = (crc >> 1) ^ poly
else:
crc >>= 1
byte >>= 1
table.append(crc)
return table
table = make_crc_table()
def crc_16_fast(msg):
crc = 0xffff
for byte in msg:
crc = table[(byte ^ crc) & 0xff] ^ (crc >> 8)
return crc ^ 0xffff
# Test
msg = bytes.fromhex("023b010000000000")
out = crc_16_fast(msg)
hi, lo = out >> 8, out & 0xff
print('{:04x} = {:02x} {:02x}'.format(out, hi, lo))
如果愿意，您可以打印 table 并将其粘贴到您的脚本中，这样您就不必在每次 运行 脚本时都计算 table .
根据引用的文件，该算法实际上是一个标准的 16 位 CCITT CRC。这可以用 crcmod.
来计算
给你：
import crcmod
# this is a standard CCITT CRC even if it does not look like
# (crcmod applies xorOut to initCrc, so initCrc is in reality 0xffff, not 0)
_CRC_FUNC = crcmod.mkCrcFun(0x11021, initCrc=0, xorOut=0xffff)
data = bytearray.fromhex("023b010000000000")
crc = _CRC_FUNC(data)
data.append(crc & 0xff)
data.append(((crc >> 8) & 0xff))
print (data.hex())
输出：
023b010000000000ff2c
crc算法有很多版本，可以从其他语言转换过来，e.x。 C代码.
table_crc_hi = [
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40]
table_crc_lo = [
0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06,
0x07, 0xC7, 0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD,
0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09,
0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A,
0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC, 0x14, 0xD4,
0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3,
0xF2, 0x32, 0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4,
0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A,
0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8, 0xE9, 0x29,
0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF, 0x2D, 0xED,
0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60,
0x61, 0xA1, 0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67,
0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F,
0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68,
0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA, 0xBE, 0x7E,
0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71,
0x70, 0xB0, 0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92,
0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C,
0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B,
0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89, 0x4B, 0x8B,
0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42,
0x43, 0x83, 0x41, 0x81, 0x80, 0x40]
def crc16(buffer, start, buffer_length):
crc_hi = 0xFF
crc_lo = 0xFF
bufferIndex = start
while True:
if(buffer_length<=0):
break
buffer_length-=1
i = crc_hi ^ buffer[bufferIndex]
bufferIndex += 1
crc_hi = crc_lo ^ table_crc_hi[i]
crc_lo = table_crc_lo[i]
return (crc_hi << 8 | crc_lo)
#return [crc_hi, crc_lo]
然后按如下方式使用。
buf= [0x2B,0xF0,0x2F,0x15,0x19,0x97,0x56,0x7,0xFE,0x0,0x53,0x83,0xBB,0x0,0x8B,0x2A,0xD3,0xDF,0x88]
crc16(buf,0,len(buf))
print("\n",37*"-","SENDER SIDE","-"*37)
def xor(a, b):
result = []
for i in range(1, len(b)):
if a[i] == b[i]:
result.append('0')
else:
result.append('1')
return ''.join(result)
def mod2div(divident, divisor):
pick = len(divisor)
tmp = divident[0: pick]
while pick < len(divident):
if tmp[0] == '1':
tmp = xor(divisor, tmp) + divident[pick]
else:
tmp = xor('0' * pick, tmp) + divident[pick]
pick += 1
if tmp[0] == '1':
tmp = xor(divisor, tmp)
else:
tmp = xor('0' * pick, tmp)
checkword = tmp
return checkword
def encodeData(data, key):
l_key = len(key)
appended_data = data + '0' * (l_key - 1)
remainder = mod2div(appended_data, key)
codeword = data + remainder
print("CRC/Remainder obtained after encoding: ", remainder)
print("Data to be transmitted at the sender side: ", codeword)
data= input("Enter the Data Bits: ")
key = input("Enter the Divisor Bits: ")
encodeData(data, key)
print("\n",36*"-","RECEIVER SIDE","-"*36)
def decodeData(data, key):
l_key = len(key)
appended_data = data + '0' * (l_key - 1)
remainder = mod2div(appended_data, key)
codeword = data + remainder
print("CRC/Remainder obtained after decoding: ", remainder)
temp = "0" * (len(key)-1)
if remainder == temp:
print("If CRC/Remainder are '0'...given data received is Correct.")
else:
print("If CRC/Remainder are not '0'...given data received is Wrong...Please try retransmission.")
data= input("Enter the Data Bits:")
key = input("Enter the Divisor Bits:")
decodeData(data, key)
print("\n",40*"-","DONE","-"*40,"\n")
我需要使用 Python 计算此 CRC，以便与 Aurora (ABB) 太阳能逆变器通信。
这是文档：http://www.drhack.it/images/PDF/AuroraCommunicationProtocol_4_2.pdf 在最后一页有计算 CRC 的说明，我需要在 python.
中进行计算我收到的消息是
MESSAGE_GRID_VOLTAGE = bytes.fromhex("023b010000000000")
结果应该是：
CRC_L = FF
CRC_H = 2C
然后我需要像这样发送带有 CRC 的消息：
MESSAGE_GRID_VOLTAGE = bytes.fromhex("023b010000000000ff2c")
我如何在 python 中做到这一点？谢谢！
这是我试过的代码：
message = "023b010000000000"
BccLo= int ("FF",16)
BccHi= int("FF", 16)
New = int(message, 16)
New = New ^ BccLo
Tmp=New << 4
New=Tmp ^ New
Tmp=New >> 5
BccLo=BccHi
BccHi= New ^ Tmp
Tmp=New << 3
BccLo=BccLo ^ Tmp
Tmp=New >> 4
BccLo=BccLo ^ Tmp
CRC_L = ~BccLo
CRC_H = ~BccHi
您需要将该算法应用于消息的每个字节。有点复杂的是，Aurora PDF 文件中给出的算法假定计算是使用 8 位无符号算法执行的。为了在 Python 中处理这个问题，我们可以使用 0xff 的位掩码。这是该代码的略微优化版本。
def crc_16(msg):
lo = hi = 0xff
mask = 0xff
for new in msg:
new ^= lo
new ^= (new << 4) & mask
tmp = new >> 5
lo = hi
hi = new ^ tmp
lo ^= (new << 3) & mask
lo ^= new >> 4
lo ^= mask
hi ^= mask
return hi << 8 | lo
# Test
msg = bytes.fromhex("023b010000000000")
out = crc_16(msg)
hi, lo = out >> 8, out & 0xff
print('{:04x} = {:02x} {:02x}'.format(out, hi, lo))
输出
2cff = 2c ff
以上代码有效，但有更简单的方法来计算 CRC。如果你需要计算很多 CRC，我们可以使用 table 来加快这个过程。
正如维基百科 Cyclic redundancy check 文章中提到的，CRC 算法通常根据编码为十六进制数的多项式来指定。这是一个使用反向多项式表示的函数。
def crc_16_CCITT(msg):
poly = 0x8408
crc = 0xffff
for byte in msg:
for _ in range(8):
if (byte ^ crc) & 1:
crc = (crc >> 1) ^ poly
else:
crc >>= 1
byte >>= 1
return crc ^ 0xffff
为了加快速度，我们可以计算 table。
def make_crc_table():
poly = 0x8408
table = []
for byte in range(256):
crc = 0
for bit in range(8):
if (byte ^ crc) & 1:
crc = (crc >> 1) ^ poly
else:
crc >>= 1
byte >>= 1
table.append(crc)
return table
table = make_crc_table()
def crc_16_fast(msg):
crc = 0xffff
for byte in msg:
crc = table[(byte ^ crc) & 0xff] ^ (crc >> 8)
return crc ^ 0xffff
# Test
msg = bytes.fromhex("023b010000000000")
out = crc_16_fast(msg)
hi, lo = out >> 8, out & 0xff
print('{:04x} = {:02x} {:02x}'.format(out, hi, lo))
如果愿意，您可以打印 table 并将其粘贴到您的脚本中，这样您就不必在每次 运行 脚本时都计算 table .
根据引用的文件，该算法实际上是一个标准的 16 位 CCITT CRC。这可以用 crcmod.
给你：
import crcmod
# this is a standard CCITT CRC even if it does not look like
# (crcmod applies xorOut to initCrc, so initCrc is in reality 0xffff, not 0)
_CRC_FUNC = crcmod.mkCrcFun(0x11021, initCrc=0, xorOut=0xffff)
data = bytearray.fromhex("023b010000000000")
crc = _CRC_FUNC(data)
data.append(crc & 0xff)
data.append(((crc >> 8) & 0xff))
print (data.hex())
输出： 023b010000000000ff2c
crc算法有很多版本，可以从其他语言转换过来，e.x。 C代码.
table_crc_hi = [
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40]
table_crc_lo = [
0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06,
0x07, 0xC7, 0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD,
0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09,
0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A,
0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC, 0x14, 0xD4,
0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3,
0xF2, 0x32, 0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4,
0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A,
0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8, 0xE9, 0x29,
0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF, 0x2D, 0xED,
0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60,
0x61, 0xA1, 0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67,
0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F,
0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68,
0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA, 0xBE, 0x7E,
0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71,
0x70, 0xB0, 0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92,
0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C,
0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B,
0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89, 0x4B, 0x8B,
0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42,
0x43, 0x83, 0x41, 0x81, 0x80, 0x40]
def crc16(buffer, start, buffer_length):
crc_hi = 0xFF
crc_lo = 0xFF
bufferIndex = start
while True:
if(buffer_length<=0):
break
buffer_length-=1
i = crc_hi ^ buffer[bufferIndex]
bufferIndex += 1
crc_hi = crc_lo ^ table_crc_hi[i]
crc_lo = table_crc_lo[i]
return (crc_hi << 8 | crc_lo)
#return [crc_hi, crc_lo]
然后按如下方式使用。
buf= [0x2B,0xF0,0x2F,0x15,0x19,0x97,0x56,0x7,0xFE,0x0,0x53,0x83,0xBB,0x0,0x8B,0x2A,0xD3,0xDF,0x88]
crc16(buf,0,len(buf))
print("\n",37*"-","SENDER SIDE","-"*37)
def xor(a, b):
result = []
for i in range(1, len(b)):
if a[i] == b[i]:
result.append('0')
else:
result.append('1')
return ''.join(result)
def mod2div(divident, divisor):
pick = len(divisor)
tmp = divident[0: pick]
while pick < len(divident):
if tmp[0] == '1':
tmp = xor(divisor, tmp) + divident[pick]
else:
tmp = xor('0' * pick, tmp) + divident[pick]
pick += 1
if tmp[0] == '1':
tmp = xor(divisor, tmp)
else:
tmp = xor('0' * pick, tmp)
checkword = tmp
return checkword
def encodeData(data, key):
l_key = len(key)
appended_data = data + '0' * (l_key - 1)
remainder = mod2div(appended_data, key)
codeword = data + remainder
print("CRC/Remainder obtained after encoding: ", remainder)
print("Data to be transmitted at the sender side: ", codeword)
data= input("Enter the Data Bits: ")
key = input("Enter the Divisor Bits: ")
encodeData(data, key)
print("\n",36*"-","RECEIVER SIDE","-"*36)
def decodeData(data, key):
l_key = len(key)
appended_data = data + '0' * (l_key - 1)
remainder = mod2div(appended_data, key)
codeword = data + remainder
print("CRC/Remainder obtained after decoding: ", remainder)
temp = "0" * (len(key)-1)
if remainder == temp:
print("If CRC/Remainder are '0'...given data received is Correct.")
else:
print("If CRC/Remainder are not '0'...given data received is Wrong...Please try retransmission.")
data= input("Enter the Data Bits:")
key = input("Enter the Divisor Bits:")
decodeData(data, key)
print("\n",40*"-","DONE","-"*40,"\n")