This one's for Lewis

You asked for a 16-bit CRC algorithm that works with the Crystalfontz CFA633-YYB-KS, and so I found one. Well, I didn't really find one. They had a C version in their docs that I ported into RB. Btw, they also have that nasty table-driven one that you found in your VB code. Yech! The reason we couldn't get the algorithm I had working is because the device requires a non-standard version of the algorithm. Essentially, the checksums all seem to "start" from a different point. So it takes a bit of extra munging.

This code should work for you, but I have to admit that I haven't tested it. I left my Keyspan at home, and my laptop has no serial ports. :-P
[rbcode]Function CRC(buffer as MemoryBlock, len as UInt16) As UInt16
dim newCRC as UInt32
dim data as UInt8
dim bit_count as Integer

newCRC = &h00F32100

dim pos as Integer
while len > 0
data = buffer.UInt8Value( pos )
pos = pos + 1

for bit_count = 0 to 7
newCRC = Bitwise.ShiftRight( newCRC, 1 )

if Bitwise.BitAnd( data, &h1 ) <> 0 then newCRC = Bitwise.BitOr( newCRC, &h00800000 )

if Bitwise.BitAnd( newCRC, &h80 ) <> 0 then newCRC = Bitwise.BitXor( newCRC, &h00840800 )

data = Bitwise.ShiftRight( data, 1 )
next bit_count

len = len - 1
wend

for bit_count = 0 to 15
newCRC = Bitwise.ShiftRight( newCRC, 1 )

if Bitwise.BitAnd( newCRC, &h80 ) <> 0 then newCRC = Bitwise.BitXor( newCRC, &h00840800 )
next bit_count

return Bitwise.ShiftRight( Bitwise.OnesComplement( newCRC ), 8 )
End Function[/rbcode]
If the code doesn't work, just email me (or post here) and I'll work on it some more. But I figure that once I get back to the office where I have a Keyspan, I'll play around with it to test it out as well. Thanks for the loaner!