[Tinyos-help] FCS - TinyOS 1.x (Tmote)

[Terence Joseph]

Thanks for that Robert I am getting the correct result now.

All the best,
Terence.


>From: "Robert Szewczyk" <szewczyk at gmail.com>
>To: "Terence Joseph" <tjormor at hotmail.com>
>CC: joe at polastre.com, tinyos-help at millennium.berkeley.edu
>Subject: Re: [Tinyos-help] FCS - TinyOS 1.x (Tmote)
>Date: Thu, 16 Nov 2006 15:00:49 -0800
>
>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 <tjormor at hotmail.com> 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" <joe at polastre.com>
>> >To: "Terence Joseph" <tjormor at hotmail.com>
>> >CC: tinyos-help at millennium.berkeley.edu
>> >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 <tjormor at hotmail.com> 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.
>> >>
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