Sure sure, copy rssi into the message someplace, assuming you
have reserved a place for it in your msg struct. This makes TOSBase
rather project dependent...
I'd have to read through the CC doc, code, and schematic to see
what exactly is being done with the strength value. I do see from
my own trivial experiments that the 'Z strength varies only a little
between "pretty-high", a "little-lower", and no-reception.
I wonder if anyone who actually worked on this can comment cogently?
MS
Sam Pierson wrote:
I tried an interesting thing today, suggested to me by one of my
professors: Copy the TOS_Msg->strength to the data section
before TOSBase actually sends it over the UART.
I did this:
pBuf->data[2]=pBuf->strength;
pBuf->data[1]=0x99;
And then from there, examine the raw packet. The values that
are copied into the data section are nothing like the 16 bits being
called strength under the old AM.h. Though, the values that I
copy into the data section change as I move the motes away
from each other. When I leave the motes at a constant distance
apart, the values stay very close together (vary by 1).
I checked the CC2420 Manual and it says that it reports the RSSI
in a range of 0-255, called LQI, link quality indicator.
Any guesses to whether the 8 bits being copied into the data
section are really the signal strength? Funny thing is, it really
only goes from about 0xFF down to about 0xD2. I would *assume*
that any signals lower than this cannot actually be picked up and
are therefore dropped anyway.
-Sam Pierson
On 1/19/06, Michael Schippling <[EMAIL PROTECTED]> wrote:
again I could be wrong about this....but my one excursion into reading
radio strength on the host side indicated that it is not actually being
sent from TOSBase. I'd like to be proved wrong on that though.
As long as you are within the TOS system itself, then everyone is
using the same TOSMsg struct and you are not faced with field
conversions.
You might want to look through the CC2420 code in platform/micaz
and see where the ADC is being pinged for the RSSI value, and what
part of the 10bits is being truncated into the 8bit field.
MS
--
Sam Pierson
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