The checksum is calculated over unencoded data stream starting after the start-of-frame delimiter (0x7e). in your example, the checksum bytes are the CRC-16 computed over
42 00 01 08 AA FF FF FF FF 04 7D (note that 7d 5d is escaped code for 7d) Best regards, Rob On 11/14/06, Terence Joseph <[EMAIL PROTECTED]> wrote:
Thanks for that but could you please tell me then what the third and second last bytes represent (F0 CE in the example below)? They are not data but come after the data field. Regards, Terence. >From: "Joe Polastre" <[EMAIL PROTECTED]> >To: "Terence Joseph" <[EMAIL PROTECTED]> >CC: [email protected] >Subject: Re: [Tinyos-help] FCS - TinyOS 1.x (Tmote) >Date: Fri, 3 Nov 2006 09:06:26 -0800 > >The FCS isn't transmitted over the serial port. > >-Joe > >On 11/1/06, Terence Joseph <[EMAIL PROTECTED]> wrote: >>Hi, >> >>I am collecting data on the serial port and I was just wondering over >>which >>fields the FCS is calculated in software as I can't seem to reproduce the >>value I see? >> >>The raw packet is the following (including esc chars): >> >>7E 42 00 01 08 AA FF FF FF FF 04 7D 5D F0 CE 7E >> >>The FCS is the third and second last byte: 0xCEFO. There is no data >>payload >>(hence 00 for 3rd byte). >> >>Over which fields is the FCS calculated? The length field is normally not >>included so I assumed it was just these byte {01 08 AA FF FF FF FF 04 7D >>5D} >>but if you check any online CRC calc. this does not prodcue 0xCEFO. >> >>Can anyone clarify. Any help is much appreciated, thanks. >> >>Best Regards, >>Terence. >> >>_________________________________________________________________ >>Discover the magic of RSS feeds at MSN Ireland! http://ie.msn.com/ >> >>_______________________________________________ >>Tinyos-help mailing list >>[email protected] >>https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help >> _________________________________________________________________ Find a baby-sitter FAST with MSN Search! http://search.msn.ie/ _______________________________________________ Tinyos-help mailing list [email protected] https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
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