[Tinyos-help] Missing SFD event on Micaz

Jun yanjunrockets at gmail.com
Sat Feb 16 17:45:48 PST 2008


Hi Phil,

I just observed the following problem you mentioned before on a micaz after
the node
transmitting a broadcast packet. Is it because microcontroller is not fast
enough to
hand the SFD event? Is there any way to get around this problem?
Is there any problem if we let sendDone returns TRUE after
condition (status & CC2420_STATUS_TX_ACTIVE) becomes true?

> There are times when on the micaz the radio says it is
> transmitting but the processor does not handle an SFD interrupt. It
> therefore needs to timeout and retry the transmission.

The true problem is that sendDone returns an ERETRY although the packet has
successfully
been
received at neighboring nodes. If we retransmit the packet upon
receiving ERETRY,
I feel that duplicated packets could be a problem.

Thank you,

Jun

On 11/1/06, Philip Levis <pal at cs.stanford.edu> wrote:
>
> On Nov 1, 2006, at 1:35 AM, Tie Luo wrote:
>
>
> > Line 6: if congestion is true, even m_cca==false can enter
> > S_SAMPLE_CCA state, which is wrong.
>
> Why is this wrong? If it's congested, continue sampling for a clear
> channel.
>
> > Line 7: I do not find where the macro PLATFORM_MICAZ is defined.
> > And, if it is defined, then micaz will always backoff regardless of
> > congestion, which is a bit wield.
>
> No. Read the code. Note that it says ABORT_PERIOD. Look at the state
> machine. There are times when on the micaz the radio says it is
> transmitting but the processor does not handle an SFD interrupt. It
> therefore needs to timeout and retry the transmission.
>
> Phil
>
>
>
>
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>



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