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 <[EMAIL PROTECTED]> 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 <[EMAIL PROTECTED]> 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
> > [EMAIL PROTECTED]
> > www.sumkino.com
> > www.wl.unn.ru
> >
> > _______________________________________________
> > Tinyos-help mailing list
> > Tinyos-help@Millennium.Berkeley.EDU
> >
https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
> >
>
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