yes, the ntp would be the implementation of a sync algorithm I was referring to… but even as that, without an RTC there's no way to be 100% percent sure as to what the time is… the most common crystals are 20 ppm, and that would introduce a drift in time… of course with regular NTP updates it could be solved, but generally wireless sensor networks don't need to know the actual date to function, just some relative time reference (as for example the uptime of the base station) --------------------------------------- Sergio Campamá sergiocamp...@gmail.com
On Feb 24, 2012, at 11:40 AM, steve ayer wrote: > hi sergio, > > not necessarily. you can certainly provide a device with a seed timestamp > that will carry through an app's runtime. there's also ntp for folks who run > an ip stack on top of their radio. > > -steve > > On 02/24/2012 09:37 AM, Sergio Campamá wrote: >> You would need a Real Time module and implement some sort of syncronization >> algorithm it yourself. There is no way for the microcontroller to guess the >> current time of day. >> >> On Fri, Feb 24, 2012 at 10:50 AM, Zhonghua<zhong...@sics.se> wrote: >> >>> Hi all, >>> >>> I want to get a time which resolution should be microsecond on Tmote Sky. >>> In my host computer and another platform E100 USRP I can use the function >>> of gettimeofday(). But through mspgcc-4.5.3, the gettimeofday() is not >>> accepted. Even after I added the time.h from my host computer's include/sys >>> directory into /usr/local/msp430/include/sys/**, it shows "undefined >>> reference to 'gettimeofday'. I checked the new added time.h, it uses an >>> external function definition, which means it will rely on an external >>> function do implement the practical function. But it seems this real >>> external function is not existing in mspgcc. I wrote the function as >>> http://svn.cod3r.com/a52codec/**trunk/liba52/src/gettimeofday.**c<http://svn.cod3r.com/a52codec/trunk/liba52/src/gettimeofday.c>directly, >>> but the ftime() function in the invoked timeb.h is still an >>> external function. I guess maybe I haven't install some necessary lib. I >>> checked I have no gnulib, I don't know does it matter? >>> I have spent too much time on that. Does anybody know how to get a >>> relatively precise resolution time on Tmote Sky? Thanks in advance! >>> >>> Sincerely, >>> >>> Zhonghua >>> >>> >>> ------------------------------------------------------------------------------ >>> Virtualization& Cloud Management Using Capacity Planning >>> Cloud computing makes use of virtualization - but cloud computing >>> also focuses on allowing computing to be delivered as a service. >>> http://www.accelacomm.com/jaw/sfnl/114/51521223/ >>> _______________________________________________ >>> Mspgcc-users mailing list >>> Mspgcc-users@lists.sourceforge.net >>> https://lists.sourceforge.net/lists/listinfo/mspgcc-users >>> >>> >> >> >> >> >> ------------------------------------------------------------------------------ >> Virtualization& Cloud Management Using Capacity Planning >> Cloud computing makes use of virtualization - but cloud computing >> also focuses on allowing computing to be delivered as a service. >> http://www.accelacomm.com/jaw/sfnl/114/51521223/ >> >> >> >> _______________________________________________ >> Mspgcc-users mailing list >> Mspgcc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/mspgcc-users > ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Mspgcc-users mailing list Mspgcc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mspgcc-users
