Thanks for your reply again. I am not sure how precise is the LocalTime interface - but since it is provided by the LocalTimeMicroC component which is wired to Msp430TimerA, (now as you said in your previous mail that the TimerA which clocks at 1Mhz) i would expect it to give near MicroSecond precision.
Moreover as LocalTime.read() is an async command, it might take some 10+ cycles handling the interrupt - which is nominal, but reduces the precision. So we might loose some precision there. Somnath Mitra On Wed, Jun 18, 2008 at 1:47 AM, Eric Decker <[EMAIL PROTECTED]> wrote: > > > On Tue, Jun 17, 2008 at 11:25 PM, Shomnat Mitra <[EMAIL PROTECTED]> wrote: > >> Thanks for the reply. >> >> One more related question. >> >> I used the LocalTimeMicroC component in Tinyos1.x, and wired the LocalTime >> interface to my application, to measure the time difference between the >> sending of a packet and receiving an ACK(using GenericComm ). >> >> I just did: >> >> sendTime = call LocalTime.read(); // just before sending >> >> and >> >> receiveTime = call LocalTime.read(); // upon receiving the ack packet >> >> and computed >> >> timeDiff = receiveTime - sendTime >> >> This is giving me values like: 14,857 >> >> So is this value in exact Microseconds? If it is - then I think I am >> getting decent values: 14.8 ms - time to send a packet and receive its ack. > > > That is how I would read it. > > In T2, I'd use TMilli and the call looks like call LocalTime.get(). Do you > really need uS resolution? > > eric > > >> >> >> Somnath Mitra >> >> >> >> On Wed, Jun 18, 2008 at 12:57 AM, Eric Decker <[EMAIL PROTECTED]> wrote: >> >>> >>> >>> On Tue, Jun 17, 2008 at 8:35 PM, Shomnat Mitra <[EMAIL PROTECTED]> >>> wrote: >>> >>>> Hello , >>>> >>>> The telosb has a 32768 Hz crystal. >>>> >>>> So the lowest precision of time that it can measure is : >>>> >>>> 1/ 32768 seconds = 30.517us >>> >>> >>> That is the underlying clock running timerB which is used to provide >>> TMilli. >>> >>>> >>>> >>>> So when we use a Timer<TMicro> interface , is this precision we get ? >>> >>> >>> TMicro is actually based on the main system clock running TimerA. It >>> clocks at 1MHz >>> and the 32K timer is used to calibrate it. This is the timing source >>> used for TMicro. You >>> really do get close to 1us ticks. >>> >>> eric >>> >>> >>>> >>>> >>>> What about LocalTime.get() 's precision ? >>>> >>>> Thanks in advance , >>>> Somnath Mitra >>>> >>>> _______________________________________________ >>>> Tinyos-help mailing list >>>> [email protected] >>>> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help >>>> >>> >>> >>> >>> -- >>> Eric B. Decker >>> Senior (over 50 :-) Researcher >>> Autonomous Systems Lab >>> Jack Baskin School of Engineering >>> UCSC >>> >> >> > > > -- > Eric B. Decker > Senior (over 50 :-) Researcher > Autonomous Systems Lab > Jack Baskin School of Engineering > UCSC >
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