[Tinyos-devel] Possible bug in broadcast code of LPL with CC2420

[David Moss]

This line of code is setting all bits in the FCF word to 0, except for the
acknowledgment bit (the key here is &= instead of =).  The acknowledgment
request bit retains whatever value it was given in layers above.

 

Thanks for double checking this,

 

-David

 

 

  _____  

From: tinyos-devel-bounces at millennium.berkeley.edu
[mailto:tinyos-devel-bounces at millennium.berkeley.edu] On Behalf Of Jun
Sent: Wednesday, April 30, 2008 11:38 AM
To: TinyOS Development
Subject: [Tinyos-devel] Possible bug in broadcast code of LPL with CC2420

 

Hi All,

I just noticed some inconsistent code for broadcast in CC2420 radio core
when LPL is enabled (tos/chips/cc2420).
Please correct me if I'm wrong.

I first found that ACK is disabled here for a broadcast packet:
lpl/DefaultLplP.nc
487       if(call AMPacket.destination(currentSendMsg) == AM_BROADCAST_ADDR)
{
488         call PacketAcknowledgements.noAck(currentSendMsg);

Then the underlying layer will overwrite the ACK flag regardless of its
previous state:
csma/CC2420CsmaP.nc
139     header->fcf &= 1 << IEEE154_FCF_ACK_REQ;

All the above codes are from the latest CVS.
 
Thank you,

Jun

-- 
--
Mailto: yanjunrockets at gmail.com 

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