ZBasic Forum

Posted: **18 June 2010, 11:57 AM**

The code below is the 8-bit counterpart to the ZBasic functions CRC16() and CRC32(). It is a general purpose routine that can be used to compute a CRC-8 value for many different CRC-8 algorithms in the same way that the built-in functions can be used. In particular, the parameters for generating a CRC compatible with the Dallas/Maxim 1-wire and with SMBus are given.

Code: Select all

'
'' CRC8
'
' This function is the CRC-8 counterpart to the ZBasic CRC16&#40;&#41; and CRC32&#40;&#41;
' functions.  See the descriptions of those routines for more information about
' the bits of the crcFlags parameter.  The Rocksoft model parameters for a
' few popular CRC-8 algorithms are given below.
'
'      Name       1-Wire    SMBus
'      -------    ------    -----
'      WIDTH           8        8
'      POLY         &H31     &H07
'      INIT            0        0
'      REFIN        True    False
'      REFOUT       True    False
'      XOROUT          0        0
'      CHECK        &HA1     &HF4
'
Function CRC8&#40;ByRef dataBuf&#40;&#41; as Byte, ByVal dataLen as UnsignedInteger, _
        ByVal crcPoly as Byte, ByVal crc as Byte, ByVal crcFlags as Byte&#41; as Byte
    Dim i as UnsignedInteger
    For i = 1 to dataLen
        Dim b as Byte
        b = dataBuf&#40;i&#41;
        If CBool&#40;crcFlags And &H01&#41; Then
            ' reflected input data
            b = FlipBits&#40;b&#41;
        End if

        Dim mask as Byte
        mask = &H80
        Do
            If CBool&#40;crc And &H80&#41; Xor CBool&#40;b and mask&#41; Then
                crc = Shl&#40;crc, 1&#41; Xor crcPoly
            Else
                crc = Shl&#40;crc, 1&#41;
            End If
            mask = Shr&#40;mask, 1&#41;
        Loop While &#40;mask <> 0&#41;
    Next i

    ' reflected output data
    If CBool&#40;crcFlags And &H02&#41; Then
        CRC8 = FlipBits&#40;crc&#41;
    Else
        CRC8 = crc
    End If
End Function

Posted: **20 April 2015, 5:42 AM**

this is my code for crc8 (tested whit zelio plc, ELSIST plc in ascii mode)

Code: Select all

Public function CRC8&#40;ByRef dataBuf&#40;&#41; as Byte,dataLen as UnsignedInteger&#41; as Byte
    Dim I As UnsignedInteger
    Dim Temp As UnsignedInteger
    Dim CRCx As UnsignedInteger
    dataLen =dataLen
    Temp = 0
    For I = 1 To dataLen 
        Temp = cuint&#40;dataBuf&#40;I&#41;&#41; + Temp
    Next I
    
    Temp = Temp Xor 65535
    Temp = Temp And 255
    Temp = Temp + 1 
    CRC8 = cbyte&#40;Temp&#41;
End function

ZBasic Forum

CRC-8 Counterpart to CRC16() and CRC32()

CRC-8 Counterpart to CRC16() and CRC32()