Dallas DS18b20 CRC code

VonSzarvas

Hello all,

With the help of several resources, including this forum post http://forums.parallax.com/showthread.php?p=574938 and some code examples by Mike Cook, I have an SX28 (SX/B) running some DS18b20 1-wire temperature sensors. The temperature streams into Hyperterminal perfectly!

Now I would like to add CRC checking. The DS18b20 datasheet explains some theory about CRC. I admit, I cannot understand it. There are many examples found on Google, but sadly for other platforms and languages. Dallas themselves do not offer assistance with the best chips, just some others...

Does anyone on this forum have a sample code or link that they have previously used ?

I guess even if its in PBasic/Stamp basic, I could likely translate it. So any pointers gratefully received.

Thank you for looking!

Max.

PJMonty

Max,

Check out this page:

www.sxlist.com/techref/ubicom/lib/io/index.htm

Half way down you'll see a bunch of links for CRC code.

Thanks,
PeterM

David B

I got the floppy disk raw sector CRC calculation working in Spin.

Floppies use a different polynomial than the Dallas chip, and for a floppy, the accumulated value is initalized to some magic number, where Dallas specifies that their value is initialized to 0.

But maybe my Spin code can be of some help. Search the propeller forum for "Floppy", select "Floppy Drive Interface" and my code is included partway down the discussion.

David

VonSzarvas

I will check it, thanks for the tip. When I get it running I will post the code here - so check back if you ever need it!!

Regards, Max.