I have this c# code that creates a CRC code. It works correctly in c#. I converted it to VB but it is not generating the correct CRC code. Could somebody please help me figure out what is wrong with the VB code.
you call GetMessageBytes with a string and get back a bytes array with the CRC added
static byte[] GetMessageBytes(string text)
{
//Get bytes for command
byte[] command = Encoding.ASCII.GetBytes(text);
//Get CRC for command bytes
ushort crc = CalculateCrc(command);
//Append CRC and CR to command
byte[] result = new byte[command.Length + 3];
command.CopyTo(result, 0);
result[result.Length - 3] = (byte)((crc >> 8) & 0xFF);
result[result.Length - 2] = (byte)((crc >> 0) & 0xFF);
result[result.Length - 1] = 0x0d;
return result;
}
static ushort CalculateCrc(byte[] pin)
{
ushort crc;
byte da;
byte ptr;
byte bCRCHign;
byte bCRCLow;
int len = pin.Length;
ushort[] crc_ta = new ushort[]
{
0x0000,0x1021,0x2042,0x3063,0x4084,0x50a5,0x60c6,0x70e7,
0x8108,0x9129,0xa14a,0xb16b,0xc18c,0xd1ad,0xe1ce,0xf1ef
};
crc = 0;
for (int index = 0; index < len; index++)
{
ptr = pin[index];
da = (byte)(((byte)(crc >> 8)) >> 4);
crc <<= 4;
crc ^= crc_ta[da ^ (ptr >> 4)];
da = (byte)(((byte)(crc >> 8)) >> 4);
crc <<= 4;
crc ^= crc_ta[da ^ (ptr & 0x0f)];
}
//Escape CR,LF,'H' characters
bCRCLow = (byte)(crc & 0x00FF);
bCRCHign = (byte)(crc >> 8);
if (bCRCLow == 0x28 || bCRCLow == 0x0d || bCRCLow == 0x0a)
{
bCRCLow++;
}
if (bCRCHign == 0x28 || bCRCHign == 0x0d || bCRCHign == 0x0a)
{
bCRCHign++;
}
crc = (ushort)(((ushort)bCRCHign) << 8);
crc |= bCRCLow;
return crc;
}
Here is the VB code.
Private Function GetMessageBytes(text As String) As Byte()
'Get bytes for command
Dim command As Byte() = System.Text.Encoding.Unicode.GetBytes(text)
'Get CRC for command bytes
Dim crc As UShort = CalcCrcHalf(command)
'Append CRC and CR to command
Dim result As Byte() = New Byte(command.Length + 3) {}
command.CopyTo(result, 0)
result(result.Length - 3) = CByte((crc >> 8) And &HFF)
result(result.Length - 2) = CByte((crc >> 0) And &HFF)
result(result.Length - 1) = &HD
Return result
End Function
Private Function CalculateCRC(pin As Byte()) As UShort
Dim crc As UShort
Dim da As Byte
Dim ptr As Byte
Dim bCRCHign As Byte
Dim bCRCLow As Byte
Dim len As Integer = pin.Length
Dim crc_ta As UShort() = New UShort() {&H0, &H1021, &H2042, &H3063, &H4084, &H50A5, &H60C6, &H70E7, &H8108, &H9129, &HA14A, &HB16B, &HC18C, &HD1AD, &HE1CE, &HF1EF}
crc = 0
For index As Integer = 0 To len - 1
ptr = pin(index)
da = CByte(CByte(crc >> 8) >> 4)
crc <<= 4
crc = crc Xor crc_ta(da Xor (ptr >> 4))
da = CByte(CByte(crc >> 8) >> 4)
crc <<= 4
crc = crc Xor crc_ta(da Xor (ptr And &HF))
Next
'Escape CR,LF,'H' characters
bCRCLow = CByte(crc And &HFF)
bCRCHign = CByte(crc >> 8)
If bCRCLow = &H28 OrElse bCRCLow = &HD OrElse bCRCLow = &HA Then
bCRCLow += 1
End If
If bCRCHign = &H28 OrElse bCRCHign = &HD OrElse bCRCHign = &HA Then
bCRCHign += 1
End If
crc = CUShort(CUShort(bCRCHign) << 8)
crc = crc Or bCRCLow
Return crc
End Function
Thanks I got it working. It was the encoding.
This is the correct code.
retrun_string = System.Text.Encoding.GetEncoding(1252).GetString(result)