请教Ti关于TX-if-CCA的问题

看SimpliciTI协议栈的family1下的Mrfi_radio.c中的MRFI_Transmit(),已经完整的实现了TX-IF-CCA的功能。

边看代码边研究吧，你想知道的MCSM1设置，RSSI阀值都有。

uint8_t MRFI_Transmit(mrfiPacket_t * pPacket, uint8_t txType)

{

#ifdef NWK_PLL

   bspIState_t s;

#endif

 uint8_t ccaRetries;

 uint8_t returnValue = MRFI_TX_RESULT_SUCCESS;

 /* radio must be awake to transmit */

 MRFI_ASSERT( mrfiRadioState != MRFI_RADIO_STATE_OFF );

 /* Turn off reciever. We can ignore/drop incoming packets during transmit. */

 Mrfi_RxModeOff();

 MRFI_PrepareToTx( pPacket );

 /* ------------------------------------------------------------------

  *    Immediate transmit

  *   ---------------------

  */

 if (txType == MRFI_TX_TYPE_FORCED)

 {

//#ifdef NWK_PLL

//    BSP_ENTER_CRITICAL_SECTION(s);

//#endif

//    MRFI_CompleteTxPrep( pPacket );

#ifdef NWK_PLL

   do

   {

   BSP_ENTER_CRITICAL_SECTION(s);

     if( stx_active == false ) // if the channel was changed

     {

       BSP_EXIT_CRITICAL_SECTION(s);

       Mrfi_RxModeOff();            // turn off the radio

       MRFI_PrepareToTx( pPacket ); // setup transmission again

       continue; // restart the loop

     }

   MRFI_CompleteTxPrep( pPacket );

   } while( 0 );

#endif

   /* Issue the TX strobe. */

   mrfiSpiCmdStrobe( STX );

#ifdef NWK_PLL

   BSP_EXIT_CRITICAL_SECTION(s);

#endif

   /* Wait for transmit to complete */

   Mrfi_DelayUsecLong( MRFI_MAX_TRANSMIT_TIME_us / 1000,

                       MRFI_MAX_TRANSMIT_TIME_us % 1000,

                       mrfi_TxImmediateDone );

   /* Clear the interrupt flag */

   MRFI_CLEAR_SYNC_PIN_INT_FLAG();

 }

 else

 {

   /* ------------------------------------------------------------------

    *    CCA transmit

    *   ---------------

    */

   MRFI_ASSERT( txType == MRFI_TX_TYPE_CCA );

   /* set number of CCA retries */

   ccaRetries = MRFI_CCA_RETRIES;

   /* For CCA algorithm, we need to know the transition from the RX state to

    * the TX state. There is no need for SYNC signal in this logic. So we

    * can re-configure the GDO_0 output from the radio to be PA_PD signal

    * instead of the SYNC signal.

    * Since both SYNC and PA_PD are used as falling edge interrupts, we

    * don't need to reconfigure the MCU input.

    */

   MRFI_CONFIG_GDO0_AS_PAPD_SIGNAL();

   /* ===============================================================================

    *    Main Loop

    *  =============

    */

   for (;;)

   {

     /* Radio must be in RX mode for CCA to happen.

      * Otherwise it will transmit without CCA happening.

      */

     /* Can not use the Mrfi_RxModeOn() function here since it turns on the

      * Rx interrupt, which we don't want in this case.

      */

     mrfiSpiCmdStrobe( SRX );

     /* wait for the rssi to be valid. */

#ifdef MRFI_TIMER_ALWAYS_ACTIVE

     MRFI_WaitTimeoutUsec(MRFI_RSSI_VALID_DELAY_US, Mrfi_ValidateRSSI);

#else // MRFI_TIMER_ALWAYS_ACTIVE

     MRFI_RSSI_VALID_WAIT();

#endif // MRFI_TIMER_ALWAYS_ACTIVE

#ifdef NWK_PLL

       BSP_ENTER_CRITICAL_SECTION(s);

       if( stx_active == false ) // if the channel was changed

       {

         BSP_EXIT_CRITICAL_SECTION(s);

         Mrfi_RxModeOff();            // turn off the radio

         MRFI_PrepareToTx( pPacket ); // setup transmission again

         continue; // restart the cca loop

       }

     MRFI_CompleteTxPrep( pPacket );

#endif

     /*

      *  Clear the PA_PD pin interrupt flag.  This flag, not the interrupt itself,

      *  is used to capture the transition that indicates a transmit was started.

      *  The pin level cannot be used to indicate transmit success as timing may

      *  prevent the transition from being detected.  The interrupt latch captures

      *  the event regardless of timing.

      */

     MRFI_CLEAR_PAPD_PIN_INT_FLAG();

     /* Issue the TX strobe. */

     mrfiSpiCmdStrobe( STX );

#ifdef NWK_PLL

     BSP_EXIT_CRITICAL_SECTION(s);

#endif

     /* Delay long enough for the PA_PD signal to indicate a

      * successful transmit. This is the 250 XOSC periods

      * (9.6 us for a 26 MHz crystal) See section 19.6 of 2500 datasheet.

      * Found out that we need a delay of atleast 20 us on CC2500 and

      * 25 us on CC1100 to see the PA_PD signal change.

      */

     Mrfi_DelayUsec(25);

     /* PA_PD signal goes from HIGH to LOW when going from RX state.

      * This transition is trapped as a falling edge interrupt flag

      * to indicate that CCA passed and the transmit has started.

      */

     if (MRFI_PAPD_INT_FLAG_IS_SET())

     {

       /* ------------------------------------------------------------------

       *    Clear Channel Assessment passed.

       *   ----------------------------------

       */

       /* Clear the PA_PD int flag */

       MRFI_CLEAR_PAPD_PIN_INT_FLAG();

       Mrfi_DelayUsecLong( MRFI_MAX_TRANSMIT_TIME_us / 1000,

                           MRFI_MAX_TRANSMIT_TIME_us % 1000,

                           mrfi_TxCCADone );

       /* transmit done, break */

       break;

     }

     else

     {

       /* ------------------------------------------------------------------

        *    Clear Channel Assessment failed.

        *   ----------------------------------

        */

       /* Turn off radio and save some power during backoff */

       /* NOTE: Can't use Mrfi_RxModeOff() - since it tries to update the

        * sync signal status which we are not using during the TX operation.

        */

       MRFI_STROBE_IDLE_AND_WAIT();

       /* flush the receive FIFO of any residual data */

       mrfiSpiCmdStrobe( SFRX );

       /* Retry ? */

       if (ccaRetries != 0)

       {

#ifdef MRFI_TIMER_ALWAYS_ACTIVE

         stx_active = false;

#endif

         /* delay for a random number of backoffs */

         Mrfi_RandomBackoffDelay();

         MRFI_PrepareToTx( pPacket ); // setup transmission again

         /* decrement CCA retries before loop continues */

         ccaRetries--;

       }

       else /* No CCA retries are left, abort */

       {

         /* set return value for failed transmit and break */

         returnValue = MRFI_TX_RESULT_FAILED;

         break;

       }

     } /* CCA Failed */

   } /* CCA loop */

 }/* txType is CCA */

 /* Done with TX. Clean up time... */

 /* Radio is already in IDLE state */

#ifdef NWK_PLL

 stx_active = false;

 // Packet transmitted, regardless of packet type, remove reference.

 sTxTimeStampAddr = NULL;

#endif

 /*

  * Flush the transmit FIFO.  It must be flushed so that

  * the next transmit can start with a clean slate.

  */

 mrfiSpiCmdStrobe( SFTX );

 /* Restore GDO_0 to be SYNC signal */

 MRFI_CONFIG_GDO0_AS_SYNC_SIGNAL();

 /* If the radio was in RX state when transmit was attempted,

  * put it back to Rx On state.

  */

 if(mrfiRadioState == MRFI_RADIO_STATE_RX)

 {

   Mrfi_RxModeOn();

 }

 return( returnValue );

}

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