No you don't understand my "position". You will have to check the radio chip specs to verify if the raw RSSI ouptut is independent of supply voltage or not. I suspect the not part, and thus made the assertion that you don't need to make adjustments to the readings as the battery droops.
You could do an experiment with a known setup and a variable power supply on your receiver. That would even give you a feel for the range of variation if I am wrong, and then you could decide if it's significantly above the noise threshold to warrant jumping through the adjustment hoops. You may find that the variation between devices is more significant... And you may find that _when_ you check the battery voltage is significant, e.g., during a transmit or not. However if I am correct in my SWAG that the radio strength voltage does vary in sync with battery voltage, comparing raw RSSI values will be just as good as any post-processed values. Anyway, good luck, and I hope you aren't trying to use this to do mote location because it doesn't work very well. MS Agnelo Silva wrote: > Michael, > > I understood your position. It really doesn't make sense to take the > battery level reading for each RSSI related to each received packet. > That's why, in my program, I will send this battery level value only if > happened a level drop (battery) based on a threshold. > Considering your idea, I will also check the battery only from times to > times (ex.: between blocks of 50 messages). > > Anyway, I will have many motes Mica2 receiving the same packet from a > sender. I need to compare their RSSI values. In terms of comparison, I > understood that can't compare "raw RSSI" values from distinct motes > (distinct battery levels) without taking in consideration that those > values are not "compatible" for a comparison because the battery level > from some motes differ from the others (like 2.9V and 2.65V). Doing so, > and finishing the dBm conversion, will produce values with some > distortion. This distortion is only irrelevant if the battery conditions > are the same for all the motes receiving the packets (for example, > starting an experiment with a brand new/same model batteries for all motes). > > What do you (and the list) think? > > []s, > Agnelo Silva > > > > > > On Mon, Jul 14, 2008 at 4:37 PM, Michael Schippling <[EMAIL PROTECTED] > <mailto:[EMAIL PROTECTED]>> wrote: > > A little aside....you CAN measure the REAL battery voltage on > the micas because they have a fixed voltage connected to > the battery measurement ADC input (at least the mica2 does, > I'm forgetting if the Z is the same now...). It's counter- > intuitive, but when you convert the fixed ref it's apparent > value _rises_ as the battery (which is used as the ADCref) > droops. Tricky engineers... > > But I stand by my opinion that you don't have to adjust for > battery voltage when converting any ratio-metric input that > uses the same battery for its power. > > MS > > Agnelo Silva wrote: > > Hi, > > I just want to get an accurate set of RSSI from a collection of > received messages. > What I understood, up to this moment, is that RSSI from the TOS > message (received packet) is a) only a raw value (we need to > convert it to a useful value, like dBm), and b) is DEPENDENT on > the battery level of the mote which received the packet. > > So, if the battery level of the mote is not considered (or > "fixed" in 3V) in our samples, it means that our set of measures > are not accurate as desired. > > I would like to confirm if I am right or not in this point. > > []s, > Agnelo Silva > > > On Mon, Jul 14, 2008 at 4:05 PM, wang wei > <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> > <mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>> > wrote: > > hi > Im not sure why do u want the"battery voltage",(Do you wanna see > differnet RSSI value under different voltage?) actually, you cant > measure the value of battery, but you can control the > transmit power > > good luck > Vi > > On Mon, Jul 14, 2008 at 11:56 AM, Agnelo Silva > <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> > <mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>> wrote: > > I am preparing the code to make the conversion of the > "raw" RSSI > value available in received message (indirectly a reading > from > ADC INPUT 0 - RSSI MONITOR). Although, I am developing > using T1 > (TinyOS 1.x), I read the T2 doc > http://docs.tinyos.net/index.php/Rssi_Demo and noted the same > thing I observed in some examples I saw in the Internet: what > are about the battery reading for each message? > > I understood that, according to the manufacturer manual, > VRSSI = > 'raw counts' * battery voltage / 1024. So, for me, the > correct > code must present a reading of the battery before sending any > 'raw RSSI' for conversion. > > Also, sometimes, I saw in some codes/messages, a direct > use of > '3' in the place of "battery voltage". Reading the > schematic of > the Mica2, I didn't see any voltage regulator to make such > assumption and I am not sure about this approach > considering the > CC1000 data sheet. > > So, what I have in mind is to develop the algorithm to send > informations to a certain procedure (internal function for > locally conversion or external program): > 1) First reading: send (battery level, raw RSSI) > 2) Next reading: if the battery level doesn't change > according > to a certain threshold, send (raw RSSI) > 3) Next reading: if the battery level does change > according to > a certain threshold, send (new battery level, raw RSSI) > > Please, I would like to hear if I misunderstood the topic "at > all" or, if not, I would like to hear different solutions or > suggestions. > > []s, > Agnelo R. Silva > > > > _______________________________________________ > Tinyos-help mailing list > Tinyos-help@millennium.berkeley.edu > <mailto:Tinyos-help@millennium.berkeley.edu> > <mailto:Tinyos-help@millennium.berkeley.edu > <mailto:Tinyos-help@millennium.berkeley.edu>> > > > > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > > > > > > ------------------------------------------------------------------------ > > > _______________________________________________ > Tinyos-help mailing list > Tinyos-help@millennium.berkeley.edu > <mailto:Tinyos-help@millennium.berkeley.edu> > > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > > _______________________________________________ Tinyos-help mailing list Tinyos-help@millennium.berkeley.edu https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
