Hexadecimal Checksum formula.

Hi Guys,

Firstly I have to say this Forum ROCKS!!!!

Thank you all for your help today and I promise it will be my last question.

I need some help in calculating a checksum as I am very over my head on this one.

Firstly the below message is in hexadecimal

F1,57,01,00,B7

B7 is the check sum.

So an example that I have seen is:

F1+57+01+00 ( Hexadecimal)

= 149 - 100 = 49 ( not sure if this is converted to decimal however F1= 0, 57 = 87, 01 = 1, 00 = 0 so total = 88 not 149??)

then 100 - 49 = B7

Apparently the above is known as 2's compliment.

The other part of the problem is these messages can vary in length.

any help or bum steer in the right direction would be appreciated.

thanks
Daniel

Originally Posted by danieljgor

Thank you all for your help today and I promise it will be my last question.

Sad to hear that

Here, try this UDF named CHECKSUM

Revised to Special-K Checksumm:

[QUOTE=Special-K;4517360]F1 in hexadecimal is 241 not 0

Interesting, I usually use the excel formula =hex2dec to convert hexadecimals into decimals and it returned a 0 but you are spot on =241!!

Thank you.

F1 is the Cell not value

=HEX2DEC("F1")