Re: [6tsch] payload format for CoAP

Xavier Vilajosana Guillen <xvilajosana@eecs.berkeley.edu> Sat, 05 October 2013 20:45 UTC

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References: <2C3A8CAFDCAFCA41B8BF705CD9471C5B18609FCD@xmb-rcd-x04.cisco.com> <C5D823CD-BBE8-473E-A0A0-42C8121EE500@tzi.org>
Date: Sat, 05 Oct 2013 13:45:01 -0700
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From: Xavier Vilajosana Guillen <xvilajosana@eecs.berkeley.edu>
To: Carsten Bormann <cabo@tzi.org>
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Cc: "Raghuram Sudhaakar (rsudhaak)" <rsudhaak@cisco.com>, "6tsch@ietf.org" <6tsch@ietf.org>
Subject: Re: [6tsch] payload format for CoAP
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Hi Carsten

can we have access to a cbor parser implementation to do some testing in a
very small microcontroller (e.g msp430).

thanks!
Xavi




On Sat, Oct 5, 2013 at 9:02 AM, Carsten Bormann <cabo@tzi.org> wrote:

> On Oct 5, 2013, at 17:29, "Raghuram Sudhaakar (rsudhaak)" <
> rsudhaak@cisco.com> wrote:
>
> >       • the additional overhead of a CBOR parser. NVPs are easy to parse.
>
> CBOR is easy to parse, too.
>
> To inject some data here, if you are talking about code size overhead:
> size -m cn-cbor.o
>         Section (__TEXT, __text): 880
>
> If all you need is name-value pairs, a tailored CBOR parser will be even
> less than those 880 bytes, which is armv7 code for a fully generic parser
> (for instance, this code includes an implementation of half-precision
> floating point.).
>
> For every single application, it is of course easy to come up with a
> bespoke format that has some advantages over CBOR but only works for this
> application, and we engineers of course like doing that :-).
> Your node may need to do other things in addition to exchanging 6tisch
> data.
> So you already may have a CBOR parser in your constrained device, which
> could make the incremental cost for using it with 6tisch near zero.
>
> Grüße, Carsten
>
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