Hi Federico,
I met the same problem. I've written a time synchronization component
for TinyOS 2.x. Currently some (very few) synchronization messages are
discarded because of the error of metadata->time (earlier than
expected).
Hope some one can point out the reason.
Regards,
Min
On 10/31/07, Federico Fiorentin <[EMAIL PROTECTED]> wrote:
> Hi all.
> The issues is the 16-bit timestamp in the received packet somethimes
> results incorrect, in that case the time result always less than what
> I aspect.
> Probably the the timestamp refers to the previous SFD signal.
>
> I tried to compare that timestmap against the time argument of the
> RadioTimeStamp.receivedSFD(uint16_t time){ }. When the timestamp is
> correct generally they are equal, in the other cases the
> RadioTimeStamp result more precise.
>
> Using:
> RadioTimeStamp.receivedSFD(uint16_t time){ }
> Now the problem is how can I determine to which kind of packet the SFD
> event is referred.
>
> Federico
>
> 2007/10/30, Miklos Maroti <[EMAIL PROTECTED]>:
> > Hi David,
> >
> > The problem is not that it overflows, but it contains an inccorect
> > value. In certain situations there are more packets in the RXFIFO and
> > we do not know how to pair up the timestamps made for the SFD and the
> > data packets. This is especially problematic if for some reason some
> > of those packets get lost or not even get into the RXFIFO.
> >
> > We should start a discussion on the Timestamping interface. I think it
> > should be allowed for the radio stack to say that it could not
> > properly timestamp the packet (just a flag) and the time synch apps
> > should check for that flag.
> >
> > Miklos
> >
> > On 10/30/07, David Moss <[EMAIL PROTECTED]> wrote:
> > > I haven't done much work with the timestamps in the CC2420 apart from
> > > Jonathan's original implementation, nor have I used it enough to have
> > > experienced any type of erratic behavior. Is the issue here that the
> > > 16-bit
> > > timestamp rolls over to 0 periodically? Would a 32-bit timestamp be
> > > better?
> > >
> > > -David
> > >
> > >
> > > -----Original Message-----
> > > From: [EMAIL PROTECTED]
> > > [mailto:[EMAIL PROTECTED] On Behalf Of Federico
> > > Fiorentin
> > > Sent: Tuesday, October 30, 2007 6:39 AM
> > > To: tinyos-help@Millennium.Berkeley.EDU
> > > Subject: [Tinyos-help] Bug in CC2420 timestamp
> > >
> > > I'm working on time synchronization with tmote sky motes and TinyOS2.
> > >
> > > I'm using a poller that sends a PollPacket every X milliseconds and a
> > > set of clients that timestamp the arrival time of the PollPacket.
> > > I found that the 16 timestamp in the time field of the Metadata are
> > > somethimes incorrect ( CC2420Packet.getMetaData(msg)->time ).
> > >
> > > This affects the 1% of the TimeStamps per mote.
> > > I compared the value "timestamp(n) - timestamp(n-1)" of two different
> > > motes.
> > >
> > > Is there any patch or a way to fix it?
> > >
> > > I appreciate any advice
> > > _______________________________________________
> > > Tinyos-help mailing list
> > > Tinyos-help@Millennium.Berkeley.EDU
> > > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
> > >
> > >
> > > _______________________________________________
> > > Tinyos-devel mailing list
> > > [EMAIL PROTECTED]
> > > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-devel
> > >
> >
> _______________________________________________
> Tinyos-help mailing list
> Tinyos-help@Millennium.Berkeley.EDU
> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
>
_______________________________________________
Tinyos-help mailing list
Tinyos-help@Millennium.Berkeley.EDU
https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
