[Tinyos-help] RSSI

[roberto pagliari]

yes, I read it, but within the tinyos code (1.0.7, for instance,
CC2420RadioM.nc) there is something like

  void tryToSend() {
     uint8_t currentstate;
     atomic currentstate = stateRadio;

     // and the CCA check is good
     if (currentstate == PRE_TX_STATE) {
       if (TOSH_READ_RADIO_CCA_PIN()) {
         atomic stateRadio = TX_STATE;
         sendPacket();
       }
      // etc...

here there's no RSSI_VALID flag check because, I guess, the radio it is
supposed to be in rxMode for at least 8 symbol periods. Do you agree?

thank you


On 7/3/07, Marco Antonio Lopez Trinidad <marco.lopez at unige.it> wrote:
>
> Hi Roberto,
>
> on the radio manual (page 51 of 90), the description of CCA pin says:
>
> The clear channel assessment signal is based on the measured RSSI value
> and a
> programmable threshold. The clear channel assessment function is used to
> implement the CSMA-CA functionality specified in [1]. CCA is valid when
> the
> receiver has been enabled for at least 8 symbol periods.
>
> bla, bla...
>
> Implementing CSMA-CA may easiest be done by using the STXONCCA command
> strobe,
> as described in the Radio control state machine section on page 44.
> Transmission will then only start if the channel is clear. The TX_ACTIVE
> status
> bit (see Table 5) may be used to detect the result of the CCA.
>
> ciao,
> --marco.
>
> > > The TOSH_READ_RADIO_CCA_PIN() can be used every time you issue a
> request
> > > to
> > > dispatch a packet, if the pin is active then you can go...
> >
> > thank you marco, but what do you mean by "if the pin is active"? CCA_PIN
> > returns the result of the operation (RSSI > CCA), but in order to read
> the
> > RSSI, the radio, I guess, need 8 symbol periods. So, I think one should
> > control the RSSI_FLAG before that, isn it?
> >
> > On 7/3/07, Aleksandr N. Sadkov <axel at wl.unn.ru> wrote:
> > >
> > > >
> > > >
> > > > On the base of what I understand for the CC2420,
> > > >
> > > > The TOSH_READ_RADIO_CCA_PIN() can be used every time you issue a
> request
> > > > to
> > > > dispatch a packet, if the pin is active then you can go...
> > > >
> > > > The RSSI value indicates if there is activity in the channel in
> order to
> > > > start
> > > > receiving a packet.
> > >
> > > What about the RSSI value for noise in this case?
> > >
> > > >
> > > > --marco.
> > >
> > >
> > >
> > > wbr, Sadkov Aleksandr
> > > axel at wl.unn.ru
> > > www.sumkino.com
> > > www.wl.unn.ru
> > >
> > > _______________________________________________
> > > Tinyos-help mailing list
> > > Tinyos-help at Millennium.Berkeley.EDU
> > >
> https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
> > >
> >
>
>
>
>
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