Hi ,
I too tried that code.Still, I receive the following output(crc stripped):
FF FF 00 7D 06 03 00 4B 00(rssi values)
FF FF 00 7D 06 04 00 46 00
FF FF 00 7D 06 05 00 4A 00
After scanning the e-mail lists,I found that :It should be converted
into decimal(Then interpreting them as dBm) and -45dBm has to be
subtracted form it,to get the correct reading.Is that correct? and they
say that the rssi value interpretation changes with tinyos version.I use
1.1.10 and mica2 motes.
When referred to CC1000 data sheet ,It has the following 2 lines in
pg.no:30:
P = -51.3 VRSSI– 49.2 [dBm] at 433 MHz
P = -50.0 VRSSI– 45.5 [dBm] at 868 MHz.
But I am using 916Mhz band.I am kind a confused with these statements
Thanks for your attention,
Kishore
Michael Schippling wrote:
Since the data[] array is bytes, only one byte (the LSB) is assigned.
One quick fix it is to do two assignments, knowing that everybody
expects multi-byte data to be in little-endian order:
data[2] = strength & 0xff;
data[3] = strength >> 8;
MS
RamKishore wrote:
Hi Michael,
You pointed the right problem.The assumption that packet length will
be automatically get adjusted at base station was wrong.When full
length messages were sent ,it really worked.*Thank you very very
much*.One small question regarding RSSI values read and interpretation.
I was trying to read counter value sent by transmitter, RSSI and crc
values with message length set to 6 .As per AM.h file,strength and
crc fields are 16 bit .To achieve this the following additions are
made to previous code.
gRxBufPoolTbl[gRxHeadIndex]->data[2] = Msg->strength;
gRxBufPoolTbl[gRxHeadIndex]->data[3] = Msg->crc;
The output is shown below:
length counter RSSI crc FF FF 00 7D 06 02 00 39 42 00 00
FF FF 00 7D 06 03 00 2D E2 00 00
FF FF 00 7D 06 04 00 2D 02 00 00
FF FF 00 7D 06 05 00 2E A2 00 00
As seen, rssi and crc values are 8bit only.I thought crc is being
over-written on remaining RSSI 8 bits, I made the following changes
to code:
gRxBufPoolTbl[gRxHeadIndex]->data[2] = Msg->strength;
gRxBufPoolTbl[gRxHeadIndex]->data[4] = Msg->crc;
I have the corresponding output:
length counter RSSI CRC FF FF 00 7D 06 02 00 39 00 42 00 00
FF FF 00 7D 06 03 00 2D 00 E2 00 00
FF FF 00 7D 06 04 00 2D 00 02 00 00
FF FF 00 7D 06 05 00 2E 00 A2 00 00
Are these values correct ; what is their interpretation?
Thank you very much for your time and patience.
Thanks once again,
Kishore
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