[Tinyos-help]Receiving Bad Packets

[RamKishore]

Hi,

 Thanks for helping in creating noisy environment.

Regarding CRCs,The CRC values that you were referring to are those over 
wired-medium(RS-232 in my case) between mica2 and PC.To elaborate:As 
said,TOS base surely doesn't do any CRC check.It receives only correct 
CRC packets from bottom layers.Now,it has to transmit this *correct 
packet* without any error to PC.So,it frames it's own CRC and transmits 
them to PC.At PC,java tool (Packetizer.java) will strip the CRC sent by  
TOSbase  ( and copy into "readCrc" of 
Packetizer.java::readFramedPacket() ) and now calculate its own CRC 
("computedCrc"  in Packetizer.java::readFramedPacket()) 
.Then,cross-checks both and if they are same,it will display.This can be 
made sure by looking at TOS_msg->crc feild and crc done by java 
tool,which will turn out to be different.

Any ideas about dealing with bottom layer files ? Is there any thing 
that can be done with these files:(they seem to be doing something with crc)
  1)tos\platform\mica2\CC1000RadioIntM.nc(I doubt something can be done 
here)
  2) tos\platform\system\CrcFilter
  3) tos\platform\CRCPacket.nc.
As a newbie,i dont know perfectly what is going on?

Many Thanks,
Kishore




Michael Schippling wrote:
> I'm "fairly sure" that TOSBase doesn't do any received CRC check.
> If you look at Packetizer.java::readFramedPacket() you can see
> where messages are rejected based on the CRC failure, so this is
> probably the place to hack.
>
> I find that jackhammers and banging on pots and pans are good for
> creating a noisy environment...sorry. You probably mean noisy RADIO
> environment. It might be easier to reduce the signal, rather than
> increase the noise. Removing the antenna from one of the motes
> or reducing the transmit power could work. Or use a partial faraday
> cage around some of the Motes.
>
> MS
>
>
> RamKishore wrote:
>> Hi all,
>>          I want to receive the  bad packets which failed CRC test.I 
>> am using  TOSbase(/tinyos1.x/contrib/xbow/apps) as receiver(mica2),at 
>> 916.4Mhz.I scanned mailing lists,but couldn't figure out anything.
>>
>> More importantly, could anyone tell me few methods of generating 
>> noisy environment.
>>
>> Many Thanks in advance,
>> Kishore
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>