Steve McKown ha scritto:
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
Thank Steve, I understand all. But I have another question now: in my
code now write in this way:
BeaconN.nc
......
uses Interface MSP430Timer;
.......
and in this file:
BeaconC.nc:
....
components new MSP430Timer32khzC() as MSP430Timer;
....
BeaconM.MSP430Timer -> MSP430Timer;
in this way do it caputer the clock that i want?
when i write: now= call MSP430Timer.get(); in now is there my clock?
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