On Tuesday 11 September 2007 12:27:31 pm Leonardo wrote: > Steve McKown ha scritto: > > On Tuesday 11 September 2007 08:48:49 am Leonardo wrote: > >> Steve McKown ha scritto: > >>> On Tuesday 11 September 2007 08:25:14 am Leonardo wrote: > >>>> Hy guy, > >>>> I need to help. I want to capture the clock of my telosb. I know that > >>>> i have to use MSP430 but how? > >>>> how can I get the clock with MSP430? > >>> > >>> Two questions: which clock do you want to get, and how do you want to > >>> get it? For the former, the msp430 maintains a number of clocks, for > >>> example, MCLK, SMCLK, ACLK. For the latter, are you wanting to expose > >>> the clock to a digital output pin for use by a bit of add-on hardware, > >>> or do you want to expose it to a software component to trigger some > >>> action? > >>> > >>> Steve > >> > >> i need to get the clock because i have to sincronized my wireless > >> network. i have to get the clock and set the clock on my telosb. i > >> didn't know that there are many clock in telosb, but I need to only one. > >> Thanks for help me > > > > You probably want to look at the msp430's Timer B, which is wired in > > TinyOS to the 32KHz crystal. This clock runs even in sleep mode, which > > is probably what you need to deal with timed radio events. The standard > > TinyOS Timer<TMilli> is a software timer attached to Timer B. There may > > be a 32KHz resolution Timer<xxx>; I don't recall off the top of my head. > > > > So I presume that you'll pass around some kind of timebase or offset in > > radio packets between nodes, when the nodes can then use to determine > > which next to transmit or receive. You probably can't manage more than a > > gross coordination without digging into the radio's software stack. > > > > If you can, try to use the LPL (low power wireless) mode of the cc2420 > > radio stack. It's already there and works pretty well. If you need > > something else, check the TEPs; there's one that covers the software > > layers in the new stack, and you could create your own layer to implement > > a new timing policy if that's what you need. > > > > Cheers, > > Steve > > Thanks for you help Steve, but I have another problem and i think my > english don't help me :D > I need to get and set the clock of my process for sicronized my > telos..... the problem is that i don't know the way to get and set the > clock.... Do you understand me now? Sorry for my english > > In my project i have to send the clock of master on network in the > beacon message. The slave get the clock and set its clock. in this way > they are sincronized because in the beacon vector there is the correcly > sequence to transmit and receive the data message. and in this way each > node rise up at the right moment.
I don't think you need synchronized clocks per se, since you can use the the beacon itself to find a common point in time (t0) between beacon sender and receivers. Then, to sechedule future events, one schedules t0 + deltaT. There's some timing feedback in the radio stack to help find t0. So all you need is a clock source with suitable granularity and precision, and a way to manage the latency between desired and actual event timings. If you are implementing something like the beaconed protocol that's part of 802.15.4, I *think* you can get by with a crystal-derived 32KHz clock, as available on the TelosB platforms. Even though the new cc2420 radio stack is modular, creating a new layer to implement a beacon-timed network protocol is going to be a big job. To get back to your original question, I'd expect you might use an Msp430Timer32khzC component for scheduling future timed events. You'll need a good understanding of the interrupts that can occur in the system which could cause your radio events to be deferred for a period. Not to mention getting to know the radio stack itself very well. If, on the other hand, you are creating something with far looser timing requirements, say a 100ms or larger granularity, then maybe you can get by with using Timer<TMilli> to set future events and using ActiveMessageC's SplitControl interface to initiate future communications at the right time. Steve _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
