[tcpdump-workers] Link type FlexRay

Guenter Ebermann guenter.ebermann at googlemail.com
Wed Jan 20 02:37:10 EST 2016


> Am 20.01.2016 um 03:00 schrieb Guy Harris <guy at alum.mit.edu>:
> 
> On Jan 19, 2016, at 5:50 PM, Guy Harris <guy at alum.mit.edu> wrote:
> 
>> OK, so the new format is that the frame begins with a measurement header, which is followed by the bitstream from the bus?

Yes. It only contains additional information. The idea is that the simplest measurement device (i.e. a device using a normal FlexRay controller), which only receives valid frames will also be able to generate the format.
In this case no error flag will be set and only valid frames will be contained in the pcap(ng) file.

>> Is the bitstream from the bus padded in that fashion?

No.

>> From the Wikipedia article on FlexRay (the first of the ISO standards the article mentions costs CHF 118, so I'm not going to buy them immediately):
>> 
>> 	https://en.wikipedia.org/wiki/FlexRay
>> 
>> a frame consists of some framing bits at each end of the frame, with each octet in the frame containing 2 bits of per-byte framing followed by the 8 bits of the octet.  Would LINKTYPE_FLEXRAY/DLT_FLEXRAY frames include all of those bits?  If so, where does the padding appear?
> 
> (I'm assuming here that one packet in a pcap or pcapng file with type LINKTYPE_FLEXRAY corresponds to a FlexRay frame, of the sort described at
> 
> 	http://www.ni.com/white-paper/3352/en/#toc4
> 
> 
> under "Frame Format".)

Yes, I will provide you with a PDF with a detailed description of the packet for further discussion.



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