On Jul 17, 2008, at 10:25 AM, Hui Kang wrote:
> Dear All:
> In my tinyos-2.x application, I would like to check the channel before
> sending a packet. By copying the following code from
> CC2420TransmitP.nc,
> I found the congest is always set as TRUE even I have only one mote
> turn
> on. Could anyone help to solve this problem or any other smarter way
> to
> check CCA? Thanks.
>
> uint8_t status;
> bool congestion = TRUE;
>
> atomic{
> call CSN.clr();
>
> status = call STXONCCA.strobe();
> if ( !( status & CC2420_STATUS_TX_ACTIVE ) ) {
> status = call SNOP.strobe();
> if ( status & CC2420_STATUS_TX_ACTIVE ) {
> congestion = FALSE;
> }
> }
> call CSN.set();
> }
>
> - Hui
>
You can't just send commands over the SPI bus. You need to go through
an arbiter and take a lock on the resource.
Phil
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