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
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--
Platform: WinXP/Cygwin
TinyOS version: 1.x, Boomerang
Programmer: MIB510
Device(s): Mica2, MicaZ, Tmote
Sensor board: homebrew
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