[Tinyos-devel] [Tinyos-help] RF230 readinf ED instead of RSSI

[Stefano "Kismet" Lenzi]

On Fri, Jun 13, 2008 at 22:58, Miklos Maroti <mmaroti at math.u-szeged.hu> wrote:
> Hi Stefano,
>
> Did you check if PacketRSSI.isValid() returns TRUE? In some cases I
> cannot guarantee that the returned ED value is correct.

I have just looked at the code and  I check PacketRSSI.isSet(),
instead of PacketRSSI.isValid(), but I think that you meant isSet(),
don't you?

>
>> 1) The required 140 microsec did not pass, but I think this is not the case
>
> After looking at the code it might be possible (although very
> unlikely) that we handle the IRQ, read the status register in 140
> microsec. I have moved the reading of the PHY_ED_LEVEL to the end of
> the reception in the attached file. Please replace your copy of
> RF230LayerP.nc with this one ang give it a try and let us know.

Probably I will have a chance to test the code today.

>
>> 2) The ED is an averaged RSSI value calculated from 8 symbols. Maybe
>> we read this value too close to the beginning of the start message and
>> we measure mostly the "silence" before the transmission. I will looki
>> at the code.
>
> Value 0 means below -91 dBm, so probably that value is not a correctly
> measured value, so ED measurement did not finish or was not performed.

I agree with your statement but, I check the PacketRSSI.isSet() so if
your patch works mean that isSet() does not return the right value all
the time.

>
> Miklos
>

Stefano Lenzi