On Mon, Sep 10, 2012 at 11:28 PM, Eric Decker <[email protected]> wrote:
> > you might try getting rid of the arbitration that is used by default. > > That is make sure that the only thing hanging off USART0 is the CC2420 and > then get rid of the resource arbiter that by default is used on the TelosB > code. > The simplest way to do this is to use Resource.immediateRequest and then never release it. > > As long as your code is running as a task (the default programming > paradigm in TinyOS (for very good reasons)) you will have potentially > non-deterministic timing. > > It depends on what else has already been posted to the task queue. > The current architecture of the code may not be capable of doing what you are trying to do. I said "MAY NOT". It depends on the timing constraints/requirements that you need for your algorithm to work properly. > eric > > > On Mon, Sep 10, 2012 at 8:44 PM, Xiaohui Liu <[email protected]> wrote: > >> Hi, >> >> To be precise, my channel switch delay is defined as the interval from >> when CC2420Config.sync() is called to CC2420Config.syncDone() event is >> triggered. >> >> On Mon, Sep 10, 2012 at 11:02 PM, Xiaohui Liu <[email protected]> wrote: >> >>> Hi everyone, >>> >>> I'm developing a protocol which requires fast switch between two >>> channels. But I find the channel switch delay varies significantly from 16 >>> to 600 jiffies, causing the sender and receiver out of sync. The major >>> cause is the non-deterministic delay to access the SPI bus, whose >>> distribution is long-tailed. Can anyone please share his/her experience on >>> how to make channel switch delay more deterministic? This may be a basic >>> issue for multi-channel protocols as discussed in related threads >>> here<http://mail.millennium.berkeley.edu/pipermail/tinyos-help/2012-May/054737.html> >>> and >>> here<https://www.millennium.berkeley.edu/pipermail/tinyos-help/2010-October/048160.html> >>> . >>> >>> One way I'm trying is to circumvent the resource arbitration of SPI bus >>> since it is merely used to access cc2420 in TelosB as seen in the >>> schematic<http://webs.cs.berkeley.edu/tos/hardware/telos/telos-revb-2004-09-27.pdf> >>> . >>> >>> Any hint will be sincerely appreciated. >>> >>> Cheers, >>> -Xiaohui Liu >>> >> >> >> >> -- >> -Xiaohui Liu >> > > > > -- > Eric B. Decker > Senior (over 50 :-) Researcher > > > -- Eric B. Decker Senior (over 50 :-) Researcher
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