The offset -45 dbm Has to be added to RSSI register as per the CC2420 datasheet
--MGM On Wed, Mar 24, 2010 at 1:32 PM, Andreas Weigel < [email protected]> wrote: > Hi, > > you should be able to find out about the details of RSSI/energy > detection in the CC2420 datasheet. I would guess (not actually using the > CC2420 myself) that the RSSI.read function directly accesses the > register and has to apply some correction on the value it finds there > whereas the other function just returns the RSSI field of the > CC2420Packet structure to which correction has already been applied > before it is stored there by the radio driver. > > By the way, if you mean "the detectable energy present on the radio > channel while the device is neither transmitting nor receiving" when you > speak of hardware noisefloor then make sure that your radio really isn't > transmitting or receiving by checking its state, otherwise your results > might be distorted (if there is not already a function providing you this). > > Andreas > > > wx li schrieb: > > Hi, Mike. > > Thanks for your help!! > > Do you means that : in ram, the rssi value is stored as a negative > > number. ( which CC2420Packet returns) > > However, in the register, the rssi > > value is stored as a positive number(which CC2420Control returns) > > I don't know whether my understanding is correct. > > Besides, I'm curious about how the rssi value is stored in the register. > > > > Thanks > > Nathan > > > > > > On Wed, Mar 24, 2010 at 2:17 AM, Chieh-Jan (Mike) Liang > > <[email protected] <mailto:[email protected]>> wrote: > > > > Here is my understanding. The RSSI returned by CC2420 is a > > negative number. Since CC2420Control returns an unsigned number, > > it needs to translate the raw RSSI to a positive number. On the > > other hand, CC2420Packet returns a signed number, so it can just > > return. > > > > Mike > > > > On Mar 23, 2010, at 4:36 AM, wx li wrote: > > > > > hi,guys. > > > I am trying to access the hardware noise floor with tinyos-2.x > > > I am confused about the code in Module "CC2420ControlP.nc" > > > > > > event void RssiResource.granted() { > > > uint16_t data; > > > call CSN.clr(); > > > call RSSI.read(&data); > > > call CSN.set(); > > > > > > call RssiResource.release(); > > > data += 0x7f; > > > data &= 0x00ff; > > > signal ReadRssi.readDone(SUCCESS, data); > > > } > > > > > > Here, i don't know why the var data should be added by 0x7F > > > And, in Module "CC2420PacketC.nc" > > > > > > async command int8_t CC2420Packet.getRssi( message_t* p_msg ) { > > > return (call CC2420PacketBody.getMetadata( p_msg ))->rssi; > > > } > > > > > > Here, it just read the rssi value in metadata, and do not plus 0x7f > > > I've been searching for the answer for a couple of hours. But > > without luck yet.. > > > Thank you for all your help! > > > > > > Regard, > > > Nathan > > > 3.23.2010 > > > > > > _______________________________________________ > > > Tinyos-help mailing list > > > [email protected] > > <mailto:[email protected]> > > > > > > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > > > > > > ------------------------------------------------------------------------ > > > > _______________________________________________ > > Tinyos-help mailing list > > [email protected] > > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > > _______________________________________________ > Tinyos-help mailing list > [email protected] > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help >
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