Thank you for the answer, David.
Now I use CC2420ReceiveC.Receive Interface and receive all the packets.
Another question: In what way does the payload returned from
CC2420ReceiveC Receive.receive(...) and the payload returned from
AMReceiveC Receive.receive(...) differ for the same packet? In my
implementation CC2420ReceiveC returns len=16 and AMReceiveC returns
len=4. The cause seems to be in CC2420ActiveMessageP where the length is
decreased by CC2420_SIZE (=header+footersize). Am I correct in the
assumption that actually it does not matter when I copy my data, because
the data is always at the same offset, where *payload is pointing to.
Can you explain the difference between the payload in CC2420ReceiveC and
AMReceiveC or point me to some litrature? (I flow over some TEPs and the
CC2420manual vom TI but found nothing specific)
M.
David Moss wrote:
Hi Mischa -
CC2420Transmit.resend(FALSE) will resend whatever has been previously loaded
into the TXFIFO on the CC2420, without using clear channel assessments.
This is one of the fastest methods of repetitively transmitting a single
packet on the CC2420, and is what the low power listening implementation
uses to wake up other nodes.
The CC2420 receiver will detect each packet separately and present those
packets to CC2420Receive. Higher up, the UniqueReceive layer of the radio
stack will filter out duplicate packets based on their DSN and source
address information. If you want to actually receive the duplicate packet,
you'll need to connect directly to CC2420ReceiveC and intercept it there.
If it makes it easier on your implementation, send a packet using low power
listening to the broadcast address. Tell the LowPowerListening interface
before send that the receiver's rx sleep interval is, say... 10 minutes.
YThen, LPL will do all the transmitting of that single packet for you as
fast as it possibly can for 10 full minutes (you'll hit send and the
sendDone will occur 10 minutes later). Of course, you can modify the
DefaultLplP implementation on your machine if you want to see when it's
calling resend().
-David
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Mischa
Weise
Sent: Wednesday, July 25, 2007 1:23 PM
To: [email protected]
Subject: [Tinyos-help] CC2420 send / resend
context:
********
I want to find out, how fast I can broadcast packets with the CC2420
Radio on the Tmote platform (under the newest TinyOS-2.x from cvs).
Therefore I send a packet burst of the same packet and measure the time
at the sender (send->sendDone-event) and at a receiver(receive-event or
SFDpinUp->SFDpinDown).
My implementation is working if I use AMSend for every single packet of
the burst. But now I want to make it faster and use
CC2420Transmit.resend(...)
Actually, I don't care about seq-no. or acks. (all acks turned off
anyway). I just want the receiver to get the payload of any broadcasted
package.
questions:
*********
Can I just use AMSend.send(AM_BROADCAST_ADDR, &pkt, paylen) and than use
CC2420Transmit.resend(FALSE) as long as I want to resend the packet at
&pkt? (to generate a packet burst of that packet)
And will the CC2420 detect each packets separately? Or will it detect
only the first such package and then discard all the following?
(There are obviously different meanings of "detect": SFD pin behavior,
TinyOS CC2420 behavior, TinyOS ActiveMessage behavior)
Thank you in advance for any answers, clues, pointers to instruction.
M.
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