> Hi, I'm a new TinyOS user and I would like to know more about > the 802.15.4 implementation on TelosB. This platform lacks a hardware clock > with sufficient precision/accuracy, but what problems does it imply > concretely > ? I actually have to use it for evaluating the performance of 802.15.4, will > it be possible using TelosB ? [...]
The IEEE 802.15.4 requires a clock with symbol granularity (16us in 2.4 GHz band), i.e. 62.500 Hz. The clock is needed, for example, to calculate beacon periods or backoffs after a CCA failure. On telosb there are two clock sources: the external 32.768 Hz quartz and the MCU-internal DCO. Unfortunately the quartz has the wrong precision and the DCO doesn't have enough accuracy (+-40 ppm is required). What the current implementation (tos/lib/mac/tkn154) does is treat one tick of the quartz as two symbols, which introduces a small error. One consequence is that when you test interoperability with a 15.4 stack that has standard-compliant timing you'll get a SYNC_LOSS (beacon-enabled mode), because the beacon intervals don't match. Jan On Wed, Feb 3, 2010 at 12:55 PM, Jonathan ROY <[email protected]> wrote: > Spam detection software, running on the system > "mail.Millennium.Berkeley.EDU", has > identified this incoming email as possible spam. The original message > has been attached to this so you can view it (if it isn't spam) or label > similar future email. If you have any questions, see > the administrator of that system for details. > > Content preview: Hi, I'm a new TinyOS user and I would like to know more > about > the 802.15.4 implementation on TelosB. This platform lacks a hardware clock > with sufficient precision/accuracy, but what problems does it imply > concretely > ? I actually have to use it for evaluating the performance of 802.15.4, will > it be possible using TelosB ? [...] > > Content analysis details: (4.6 points, 3.3 required) > > pts rule name description > ---- ---------------------- -------------------------------------------------- > 1.4 MSGID_MULTIPLE_AT Message-ID contains multiple '@' characters > 3.2 FH_DATE_PAST_20XX The date is grossly in the future. > 0.0 HTML_MESSAGE BODY: HTML included in message > 0.0 BAYES_50 BODY: Bayesian spam probability is 40 to 60% > [score: 0.5000] > > The original message was not completely plain text, and may be unsafe to > open with some email clients; in particular, it may contain a virus, > or confirm that your address can receive spam. If you wish to view > it, it may be safer to save it to a file and open it with an editor. > > > _______________________________________________ > Tinyos-help mailing list > [email protected] > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
