I just looked at the mica2 code and I think was wrong:
Only TOS_Msg.length bytes of payload are transmitted.
There's a bunch of swapping around of lengths but it looks
like the Msg.length is used to xmit only that number of bytes.
So, even if you have a large TOSH_DATA_LENGTH you don't
loose bandwidth when sending small payloads.
meaculpa...
MS
Heo Heo wrote:
Mike,
I followed your advice and run ListenRaw. With different payload
sizes, the packet sizes in ListenRaw are also different. So, I guess
TinyOS only transmit the actual payload, not the paddings.
Thanks for your advice.
Heo
*/Michael Schippling <[EMAIL PROTECTED]>/* wrote:
I'd have to go read the radio code again because I wasn't looking
for this when I did...but I think the transmitter tags the crc onto
the end of the full packet. The length field would then just tell
you how many bytes are significant.
If you have a setup with a short message you can use ListenRaw to
see what is actually coming over the serial. Whether that's the same
as the radio is a code-review issue...
MS
Heo Heo wrote:
> Mike,
>
> I think we may be wrong on this. There is a field named "length" in
> the TOSMsg structure. This field indicates the actual length of the
> payload. So I guess the radio layer only transmits the actual
bytes used.
>
> This thought also came from the fact that when I run "listen" on the
> PC side, it only shows the actual bytes used, not the paddings.
>
> Since I am a newbie, I may be wrong again.
>
> Best,
> Heo
>
>
>
> */Michael Schippling /* wrote:
>
> I believe that is correct. The payload size is always
TOS_DATA_LENGTH,
> no matter how many bytes are actually used...
> MS
>
>
> Heo Heo wrote:
> > Mike,
> >
> > I was thinking of a different approach. In the OscopeMsg
> structure, I
> > put some extra fields for the TOS_Msg header fields. On the mote
> running
> > TOSBase, I copied the TOS_Msg header fields to these Java-based
> > structures. That should work.
> >
> > The downside of this approach is there are soem unnecessary
> fields in
> > the original OscopeMsg structure. Besides, the TOSBase code is not
> > "transparent" anymore.
> >
> > I have a question: since TOS_DATA_LENGTH is a constant which
defines
> > the size of the payload of the TOS message. Does it mean that the
> size
> > of the packet transmitted over the air is always fixed (i.e. equal
> > TOS_DATA_LENGTH + size of some header fields), regardless of how
> little
> > the real payload is.
> >
> > Thanks a lot
> > Heo
> >
> >
> > */Michael Schippling /* wrote:
> >
> > Warning: answer only relevant to TOS1.x...
> >
> > I was going to say just look at the Message classes:
> > net/tinyos/message/Message.java
> > net/tinyos/oscope/OscopeMsg.java
> > and the doc for MIG (which generates OscopeMsg.java).
> >
> > But when I did (because I just refused to use them from
> > the outset so I never did before) I found that there are
> > no builtin accessors for the message header. And what's
> > more the way to get to arbitrary fields is:
> >
> > protected long getUIntElement(int offset, int length)
> >
> > So you can't use it from outside OscopeMsg. Somehow I have
> > come to expect this sort of thing but it still annoys me...
> >
> >
> > So your two options are A) extend OscopeMsg and add accessors
> > that call getUIntElement() using your own special knowledge of
> > the header structure gleaned from tos/types/AM.h; or, B) write
> > the whole thing yourself (assuming you are not just modifying
> > the oscope app...). For an example of the DIY option see my code:
> > http://www.etantdonnes.com/Motes/robocode.tar.gz
> >
> > MS
> >
> > Heo Heo wrote:
> > > I was wondering if there is a way to access the TOS_Msg fields
> (like
> > > addr, type, group, strength, etc.) from Java.
> > >
> > > The context is that there is a mote running OscilloscopeRF. This
> > mote
> > > sends messages (class OscopeMsg) to the base station (connected
> > to PC
> > > with Serial forwarder). For each message received at the PC, our
> > Java
> > > program (running on the PC) needs to access some fields of the
> > TOS_Msg
> > > header.
> > >
> > > Thanks a lot for any help.
> > >
> > >
> > >
> > >
> > > Everyone is raving about the all-new Yahoo! Mail beta.
> > >
> > >
> > >
> > >
> > >
> >
>
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