[Tinyos-help] Precise contents and length of the 802.15.4 frames (and most especially with the TestNetwork App)

[Pedro Almeida]

Brian,

Great! That really helped!  Thank you!

Best regards,

Pedro

On 6/30/07, Brian Mulanda <bmulanda.tinyos at gmail.com> wrote:
>
> Pedro,
>
> In terms of  memory allocation, the data bytes are always 28. However,
> during transmission, usually,
> only the actual data bytes (in your case, the size of the struct) are
> relayed.
>
> -Brian
>
>
> On 6/30/07, Pedro Almeida <pedralm at gmail.com> wrote:
> >
> > Hey, Brian!
> >
> > So that means it always is 28 bytes, regardless of being "filled" or
> > not? So if my struct is 1 or 28 bytes, the data bytes are always 28?
> >
> > Thanks!
> >
> >
> > On 6/30/07, Brian Mulanda <bmulanda.tinyos at gmail.com> wrote:
> > >
> > >
> > > TOSH_DATA_LENGTH represents the max data payload; in your case, the
> > > struct. The size of
> > > the struct is allocated out of the 28 bytes.
> > >
> > > I am not certain of the total frame size; I think it is,
> > > coincidentally, at least 28 (13+15). In the event
> > > that escape bytes are included, to handle "reserved" bytes appearing
> > > in the data, it could be more.
> > >
> > > -Brian
> > >
> > > On 6/29/07, Pedro Almeida <pedralm at gmail.com> wrote:
> > >
> > > > Hello all;
> > > >
> > > > I would like to know the exact length of the 802.15.4 frame. The
> > > > reason that i'd like to know the exact length is because i need to do some
> > > > duty cycles numbers and one of the inputs is the frame length. It would seem
> > > > to equal the payload, but given it makes no sense to me the payload on the
> > > > serial frame, i might as well doubt i can figure the length on the
> > > > 802.15.4's.
> > > >
> > > > So according to TEP 125:
> > > >
> > > > The TinyOS 802.15.4 T-frame format is as follows:
> > > >
> > > > +-------------------+---------+------------------------------+--------------+
> > > > | 802.15.4 Header | AM type | data | 802.15.4 CRC |
> > > >
> > > > +-------------------+---------+------------------------------+--------------+
> > > >
> > > > I presume the 802.15.4 Header, as according to CC2420.h, to be 10
> > > > bytes:
> > > >
> > > > typedef nx_struct cc2420_header_t {
> > > > nxle_uint8_t length;
> > > > nxle_uint16_t fcf;
> > > > nxle_uint8_t dsn;
> > > > nxle_uint16_t destpan;
> > > > nxle_uint16_t dest;
> > > > nxle_uint16_t src;
> > > >
> > > > /** I-Frame 6LowPAN interoperability byte */
> > > > #ifdef CC2420_IFRAME_TYPE
> > > > nxle_uint8_t network;
> > > > #endif
> > > >
> > > > nxle_uint8_t type;
> > > > } cc2420_header_t;
> > > >
> > > > AM Type, according to previous struct, another byte before "data".
> > > > Total: 11.
> > > >
> > > > I suppose CRC to be 2 extra bytes added in the end. Total: 13
> > > >
> > > > The "data" field intrigues me.
> > > >
> > > > I see this being defined in CC2420.h
> > > >
> > > > #ifndef TOSH_DATA_LENGTH
> > > > #define TOSH_DATA_LENGTH 28
> > > > #endif
> > > >
> > > > Does this mean it's a fixed length that gets 'populated' according
> > > > to each different situation (making a fixed total of 42 bytes), or is 28 a
> > > > max, or am i understanding this all wrong?
> > > > The struct in TestNetwork is 15 bytes. Would that means the total
> > > > frame size is 13+15=28 bytes? Or is there anything extra added?
> > > >
> > > > Any help greatly appreciated!
> > > > Thanks,
> > > >
> > > > Pedro
> > > >
> > > >
> > > > _______________________________________________
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> > > > Tinyos-help at Millennium.Berkeley.EDU
> > > > https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
> > > >
> > > >
> > >
> > >
> >
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>
>
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