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byte[] array = { 0x01, 0x03, 0x00, 0x01, 0x00, 0x01 };
ushort u = CRC(array);
Console.WriteLine(u.ToString("X4"));
Python
def CalculateCRC(data):
    crc = 0xFFFF
    for pos in data:
        crc ^= pos
        for i in range(len(data)-1, -1, -1):
            if ((crc & 0x0001) != 0):
                crc >>= 1
                crc ^= 0xA001
            else:
                crc >>= 1
    return crc
Which I run like this:
data = bytearray.fromhex("010300010001")
crc = CalculateCRC(data)
print("%04X"%(crc))
The result from the C# example is: 0xCAD5.
The result from the Python example is: 0x8682.
I know from fact by other applications that the CRC should be 0xCAD5, as the C#-example provides.
When I debug both examples step-by-step, the variable 'crc' has difference values after these code lines:
crc ^= (UInt16)data[pos];
crc ^= pos
What am I missing?
/Mc_Topaz
Your inner loop uses the size of the data array instead of a fixed 8 iterations. Try this:
def calc_crc(data):
    crc = 0xFFFF
    for pos in data:
        crc ^= pos 
        for i in range(8):
            if ((crc & 1) != 0):
                crc >>= 1
                crc ^= 0xA001
            else:
                crc >>= 1
    return crc
data = bytearray.fromhex("010300010001")
crc = calc_crc(data)
print("%04X"%(crc))
        
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