On 3/6/08, Michael Schippling <[EMAIL PROTECTED]> wrote:
>
> oops....I see, you are getting the wrong length,
> now that I try to read the debug lines of you message...
> I've run "as fast as I can" using micaz and T1, but
> not tmotes so I've never seen this happen.
>
> Can you tell from the data if you are missing the last
> byte of your packet? Can you try looking into the receive
> loop to see how many bytes you really get? I think the
> user level buffer may be allocated to the 'length' size
> and copied, but you might find your missing byte in
> the underlying code.
The data length of Our packet is 74. In fact, almost all corrupted
packets have a payload of 5 bytes. Sometimes it is 9 or others.
I don't remember clearly and I'm too lazy to go look, but
> I think the receiving code uses the length from the message
> as the number of bytes to receive and put into the buffer
> you get. So two (or more) things would seem to be going wrong,
> A) the actual message length gets changed from 10 to 9,
> B) the 'extra' byte is either not transmitted, or is somehow
> silently dropped in the receiver without a "resync" complaint.
In my test, when corrupted packets are detected, it seems that crc check
is correct. If the length is wrong, crc check should not pass, since length
is also taken into account when calculation.
You seem to have validated that the message is good as it
> leaves the sending UART, and perhaps even at the receiver.
> If there's some way to really check that your message has
> the correct length prior to UART send, that would nail it.
> Then putting trace messages in strategic locations of
> Packetizer is probably the only way to chase it down.
Just now, in my test, it shows that before packets are sent to UART, the
packet length is correct(Led is turn on). On the contrary, in UART some
packets have wrong length. Therefore, UART may be the true reason. But if it
is related to UART, why it only happen to Telosb and Imote2, but not micaz.
not much use, I know...
> MS
>
>
>
> renjie huang wrote:
> > Hi *Michael *
> > In fact, I do not do my own CRC check in java code. The problem is that
> > my java program occasionally receive some corrupted packets, which cause
> > some exception when java program processes them. In my test , the crc
> > check in Packetizer is correct although the packet is corrupted.
> >
> > Since crc check is done, they should be discarded. I don't know where
> > the corrupted packets come from and where they are corrupted.
> >
> > On 3/6/08, *Michael Schippling* <[EMAIL PROTECTED]
> > <mailto:[EMAIL PROTECTED]>> wrote:
> >
> > Are you doing your own CRC check in your Java code after receiving
> > a message via Packetizer? I would think Packetizer should catch
> > bad CRC's so your own check would be redundant. If you have written
> > your own CRC code that's a likely culprit...
> >
> > MS
> >
> > renjie huang wrote:
> > > Our java program occasionally receives some corrupted packet as
> > > following. I think there are two possible places where a packet
> is
> > > corrupted.
> > > 1. CC2420RadioM
> > > Our case is a bit similar to that is reported by
> > >
> >
> http://mail.millennium.berkeley.edu/pipermail/tinyos-help/2006-August/018704.html
> .
> > > Our data rate is also high, and we also use CC2420 radio chip(on
> > iMote2).
> > > But the difference is that we don't use TOSBase. When the sink
> > forwards
> > > packets that are received from radio to UART, there is a crc
> check in
> > > AMStandard.nc. So if the packet is corrupted, it should be thrown
> > away,
> > > but not forwarded to UART. Therefore it seems that it may be not
> a
> > > corrupted packet from CC2420.
> > >
> > > 2. UART transmission
> > > I check the code of FrameM.nc, crc calculation is done in
> > > async event result_t ByteComm.txByteReady(bool
> > LastByteSuccess) ,
> > > In Packetizer.java, crc is also checked. Therefore it also seems
> that
> > > the packet is not corrupted in UART.
> > >
> > > I am very confused about this. Is it because CRC is not reliable
> to
> > > check corrupted packets? But in our experiment, it seems that
> > corrupted
> > > packets are received only when packet rate is high. Thanks.
> > >
> > >
> > > Dropping com.oasis.message.NetworkMsg (AM type 129): invalid
> > length (too
> > > short), template.length=10, real length=9 Received message:09 21
> > 08 49
> > > FF FF 7E 00 81 7D 0A 00 08 00 02 00 01 9D A5 Dropping
> > > com.oasis.message.NetworkMsg (AM type 129): invalid length (too
> > short),
> > > template.length=10, real length=9 Received message:09 21 08 49 FF
> > FF 7E
> > > 00 81 7D 0A 00 08 00 02 00 01 9D A5 Dropping
> > > com.oasis.message.NetworkMsg (AM type 129): invalid length (too
> > short),
> > > template.length=10, real length=9 Received message:09 21 08 49 FF
> > FF 7E
> > > 00 81 7D 0A 00 08 00 02 00 01 9D A5 Dropping
> > > com.oasis.message.NetworkMsg (AM type 129): invalid length (too
> > short),
> > > template.length=10, real length=9 Received message:09 21 08 49 FF
> > FF 7E
> > > 00 81 7D 0A 00 08 00 02 00 01 9D A5 Dropping
> > > com.oasis.message.NetworkMsg (AM type 129): invalid length (too
> > short),
> > > template.length=10, real length=9 Received message:09 21 08 49 FF
> > FF 7E
> > > 00 81 7D 0A 00 08 00 02 00 01 9D A5 Dropping
> > > com.oasis.message.NetworkMsg (AM type 129): invalid length (too
> > short),
> > > template.length=10, real length=9 Received message:09 21 08 49 FF
> > FF 7E
> > > 00 81 7D 0A 00 08 00 02 00 01 9D A5 Dropping
> > > com.oasis.message.NetworkMsg (AM type 129): invalid length (too
> > short),
> > > template.length=10, real length=9 Received message:09 21 08 49 FF
> > FF 7E
> > > 00 81 7D 0A 00 08 00 02 00 01 9D A5
> > >
> > >
> > >
> > > --
> > >
> > > Renjie
> > >
> > >
> > >
> >
> ------------------------------------------------------------------------
> > >
> > > _______________________________________________
> > > Tinyos-help mailing list
> > > Tinyos-help@millennium.berkeley.edu
> > <mailto:Tinyos-help@millennium.berkeley.edu>
> > >
> >
> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
> >
> > --
> > Platform: WinXP/Cygwin
> > TinyOS version: 1.x, Boomerang
> > Programmer: MIB510
> > Device(s): Mica2, MicaZ, Tmote
> > Sensor board: homebrew
> >
> >
> >
> >
> > --
> >
> > Renjie
>
> --
> Platform: WinXP/Cygwin
> TinyOS version: 1.x, Boomerang
> Programmer: MIB510
> Device(s): Mica2, MicaZ, Tmote
> Sensor board: homebrew
>
>
--
Renjie
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