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Posted: **Fri Jan 04, 2013 2:21 am**

I have written a quick script in basic to create a XOR checksum but now I'm working on CRC-CCITT

http://en.wikipedia.org/wiki/Computation_of_CRC
http://www.lammertbies.nl/comm/info/crc ... ation.html

If I could address individual bits I'd be on my way. Is there any way to do this?

At the moment I'm defining variables as BYTE as doing LOTS of XOR and manually checking bytes, doing >> and adding 128

Has anyone implemented CRC-CCITT (0xFFFF) before? I'm not sure I'm going down the correct avenue.

Posted: **Mon Jan 07, 2013 7:43 pm**

C and BASIC manipulate bits pretty much the same way. Mask a bit with & (C) AND (BASIC) with a hex value x AND (1<<5) chooses bit 5. Or you could write x AND 0x20

You could write functions to do it, but that would slow you down.

There are lots of examples of calculating different CRC and it should be fairly easy to move them over to BASIC.

Posted: **Mon Jan 07, 2013 11:04 pm**

You could always create a macro to do bit set, clear or test -- I'm just so use to seeing the AND (1<<x) in code

Code: Select all

#define BITSET(x,bit)        (x  OR (1<<bit))
#define BITCLEAR(x,bit)      (x AND NOT(1<<bit))
#define TESTBIT(x,bit)       (x AND (1<<bit))

Posted: **Tue Jan 15, 2013 12:39 am**

That clear thing up. Now to port and post the function. Cheers

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Computing CRC-CCITT (0xFFFF)

Computing CRC-CCITT (0xFFFF)

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Re: Computing CRC-CCITT (0xFFFF)