예제 #1
0
/**************************************************************************************************
 * @fn          MRFI_Transmit
 *
 * @brief       Transmit a packet.
 *
 * @param       pPacket - pointer to packet to transmit
 *              txType  - FORCED or CCA
 *
 * @return      Return code indicates success or failure of transmit:
 *                  MRFI_TX_RESULT_SUCCESS - transmit succeeded
 *                  MRFI_TX_RESULT_FAILED  - transmit failed because CCA failed
 **************************************************************************************************
 */
uint8_t MRFI_Transmit(mrfiPacket_t * pPacket, uint8_t txType)
{
  uint8_t txResult = MRFI_TX_RESULT_SUCCESS;
  static uint8_t dsn = 0;

  /* radio must be awake to transmit */
  MRFI_ASSERT( mrfiRadioState != MRFI_RADIO_STATE_OFF );

  /* TX_DONE line status must be low. If high, some state logic problem. */
  MRFI_ASSERT(!MRFI_TX_DONE_STATUS());


  /* Turn off reciever. We ignore/drop incoming packets during transmit. */
  Mrfi_RxModeOff();


  /* --------------------------------------
   *    Populate the IEEE fields in frame
   *   ------------------------------------
   */

  /* set the sequence number, also known as DSN (Data Sequence Number) */
  pPacket->frame[MRFI_DSN_OFFSET]   = dsn++;
  pPacket->frame[MRFI_FCF_OFFSET]   = MRFI_FCF_0_7;
  pPacket->frame[MRFI_FCF_OFFSET+1] = MRFI_FCF_8_15;


  /* ------------------------------------------------------------------
   *    Write packet to transmit FIFO
   *   --------------------------------
   */
  {
    uint8_t txBufLen;
    uint8_t frameLen;
    uint8_t *p;

    /* flush FIFO of any previous transmit that did not go out */
    MRFI_RADIO_FLUSH_TX_BUFFER();

    /* set point at beginning of outgoing frame */
    p = &pPacket->frame[MRFI_LENGTH_FIELD_OFFSET];

    /* get number of bytes in the packet (does not include the length byte) */
    txBufLen = *p;

    /*
     *  Write the length byte to the FIFO.  This length does *not* include the length field
     *  itself but does include the size of the FCS (generically known as RX metrics) which
     *  is generated automatically by the radio.
     */
    frameLen = txBufLen + MRFI_RX_METRICS_SIZE;

    mrfiSpiWriteTxFifo(&frameLen, 1);

    /* skip the length field which we already sent to FIFO. */
    p++;
    /* write packet bytes to FIFO */
    mrfiSpiWriteTxFifo(p, txBufLen);
  }

  /* Forced transmit */
  if(txType == MRFI_TX_TYPE_FORCED)
  {
    /* NOTE: Bug (#1) described in the errata swrz024.pdf for CC2520:
     * We never strobe TXON when the radio is in receive state.
     * If this is changed, must implement the bug workaround as described in the
     * errata (flush the Rx FIFO).
     */

    /* strobe transmit */
    mrfiSpiCmdStrobe(STXON);

    /* wait for transmit to complete */
    while (!MRFI_TX_DONE_STATUS());

    /* Clear the TX_FRM_DONE exception flag register in the radio. */
    mrfiSpiBitClear(EXCFLAG0, 1);
  }
  else /* CCA Transmit */
  {
    /* set number of CCA retries */
    uint8_t ccaRetries = MRFI_CCA_RETRIES;

    MRFI_ASSERT( txType == MRFI_TX_TYPE_CCA );

    /* ======================================================================
    *    CCA Algorithm Loop
    * ======================================================================
    */
    while(1)
    {
      /* Turn ON the receiver to perform CCA. Can not call Mrfi_RxModeOn(),
      * since that will enable the rx interrupt, which we do not want.
      */
      mrfiSpiCmdStrobe(SRXON);

      /* Wait for RSSI to be valid. */
      MRFI_RSSI_VALID_WAIT();

      /* Request transmit on cca */
      mrfiSpiCmdStrobe(STXONCCA);

      /* If sampled CCA is set, transmit has begun. */
      if(MRFI_SAMPLED_CCA())
      {
        /* wait for transmit to complete */
        while( !MRFI_TX_DONE_STATUS() );

        /* Clear the TX_FRM_DONE exception flag register in the radio. */
        mrfiSpiBitClear(EXCFLAG0, 1);

        /* transmit is done. break out of CCA algorithm loop */
        break;
      }
      else
      {
        /* ------------------------------------------------------------------
         *    Clear Channel Assessment failed.
         * ------------------------------------------------------------------
         */

        /* Retry ? */
        if(ccaRetries != 0)
        {
          /* turn off reciever to conserve power during backoff */
          Mrfi_RxModeOff();

          /* delay for a random number of backoffs */
          Mrfi_RandomBackoffDelay();

          /* decrement CCA retries before loop continues */
          ccaRetries--;
        }
        else  /* No CCA retries left, abort */
        {
          /* set return value for failed transmit and break */
          txResult = MRFI_TX_RESULT_FAILED;
          break;
        }
      }
    } /* End CCA Algorithm Loop */
  }

  /* turn radio back off to put it in a known state */
  Mrfi_RxModeOff();

  /* If the radio was in RX state when transmit was attempted,
   * put it back in RX state.
   */
  if(mrfiRadioState == MRFI_RADIO_STATE_RX)
  {
    Mrfi_RxModeOn();
  }

  /* return the result of the transmit */
  return( txResult );
}
예제 #2
0
/**************************************************************************************************
 * @fn          MRFI_Init
 *
 * @brief       Initialize MRFI.
 *
 * @param       none
 *
 * @return      none
 **************************************************************************************************
 */
void MRFI_Init(void)
{
  /* Configure Output lines */
  MRFI_CONFIG_RESETN_PIN_AS_OUTPUT();
  MRFI_CONFIG_VREG_EN_PIN_AS_OUTPUT();

  /* Configure Input lines */
  MRFI_CONFIG_TX_FRAME_DONE_AS_INPUT();
  MRFI_CONFIG_FIFO_AS_INPUT();
  MRFI_CONFIG_FIFOP_AS_INPUT();

  /* Initialize SPI */
  mrfiSpiInit();

  /* Power up the radio chip */
  Mrfi_TurnOnRadioPower();

  /* Confirm that we are talking to the right hardware */
  MRFI_ASSERT(mrfiSpiReadReg(CHIPID) == MRFI_RADIO_PARTNUM);


  /* Random Number Generator:
   * The seed value for the randon number generator logic
   * is derived from the radio.
   */

  /* Set radio in rx mode, but with symbol search disabled. Used for RSSI
   * measurments or when we don't care about the received frames.
   */
  mrfiSpiWriteReg(FRMCTRL0, FRMCTRL0_RESET_VALUE | RX_MODE_RSSI_ONLY);

  /* Turn on the receiver */
  mrfiSpiCmdStrobe(SRXON);

  /*
   *  Wait for RSSI to be valid. RANDOM command strobe can be used
   *  to generate random number only after this.
   */
  MRFI_RSSI_VALID_WAIT();


  /* Get random byte from the radio */
  mrfiRndSeed = mrfiSpiRandomByte();

 /*
  *  The seed value must not be zero.  If it is, the pseudo random sequence
  *  will be always be zero. There is an extremely small chance this seed could
  *  randomly be zero (more likely some type of hardware problem would cause
  *  this). If it is zero, initialize it to something.
  */
  if(mrfiRndSeed == 0)
  {
      mrfiRndSeed = 0x80;
  }

  /* Random number initialization is done. Turn the radio off */
  Mrfi_TurnOffRadioPower();

  /* Initial radio state is - OFF state */
  mrfiRadioState = MRFI_RADIO_STATE_OFF;

  /**********************************************************************************
   *                            Compute reply delay scalar
   *
   * The IEEE radio has a fixed data rate of 250 Kbps. Data rate inference
   * from radio regsiters is not necessary for this radio.
   *
   * The maximum delay needed depends on the MAX_APP_PAYLOAD parameter. Figure
   * out how many bits that will be when overhead is included. Bits/bits-per-second
   * is seconds to transmit (or receive) the maximum frame. We multiply this number
   * by 1000 to find the time in milliseconds. We then additionally multiply by
   * 10 so we can add 5 and divide by 10 later, thus rounding up to the number of
   * milliseconds. This last won't matter for slow transmissions but for faster ones
   * we want to err on the side of being conservative and making sure the radio is on
   * to receive the reply. The semaphore monitor will shut it down. The delay adds in
   * a fudge factor that includes processing time on peer plus lags in Rx and processing
   * time on receiver's side.
   *
   * **********************************************************************************
   */
#define   PLATFORM_FACTOR_CONSTANT    2
#define   PHY_PREAMBLE_SYNC_BYTES     8

  {
    uint32_t bits, dataRate = 250000;

    bits = ((uint32_t)((PHY_PREAMBLE_SYNC_BYTES + MRFI_MAX_FRAME_SIZE)*8))*10000;

    /* processing on the peer + the Tx/Rx time plus more */
    sReplyDelayScalar = PLATFORM_FACTOR_CONSTANT + (((bits/dataRate)+5)/10);
  }

  /* Random delay: This prevents devices on the same power source from repeated
   *  transmit collisions on power up.
   */
  Mrfi_RandomBackoffDelay();

  BSP_ENABLE_INTERRUPTS();
}
예제 #3
0
/**************************************************************************************************
 * @fn          MRFI_Init
 *
 * @brief       Initialize MRFI.
 *
 * @param       none
 *
 * @return      none
 **************************************************************************************************
 */
void MRFI_Init(void)
{
  /* ------------------------------------------------------------------
   *    Run-time integrity checks
   *   ---------------------------
   */
  memset(&mrfiIncomingPacket, 0x0, sizeof(mrfiIncomingPacket));

  /* verify the correct radio is installed */
  MRFI_ASSERT( CHIPID == MRFI_RADIO_PARTNUM );      /* wrong radio */
  MRFI_ASSERT( CHVER  >= MRFI_RADIO_MIN_VERSION );  /* obsolete radio version */

  /* ------------------------------------------------------------------
   *    Configure IO ports
   *   ---------------------------
   */

#if defined(MRFI_PA_LNA_ENABLED) && defined(BSP_BOARD_SRF04EB)
  MRFI_BOARD_PA_LNA_CONFIG_PORTS();
  MRFI_BOARD_PA_LNA_HGM();
#endif


  /* ------------------------------------------------------------------
   *    Configure clock to use XOSC
   *   -----------------------------
   */
  SLEEPCMD &= ~OSC_PD;                       /* turn on 16MHz RC and 32MHz XOSC */
  while (!(SLEEPSTA & XOSC_STB));            /* wait for 32MHz XOSC stable */
  asm("NOP");                             /* chip bug workaround */
  {
    uint16_t i;

    /* Require 63us delay for all revs */
    for (i=0; i<504; i++)
    {
      asm("NOP");
    }
  }
  CLKCONCMD = (0x00 | OSC_32KHZ);            /* 32MHz XOSC */
  while (CLKCONSTA != (0x00 | OSC_32KHZ));
  SLEEPCMD |= OSC_PD;                        /* turn off 16MHz RC */


  /* Configure radio registers that should be different from reset values. */
  Mrfi_RadioRegConfig();

  /* ------------------------------------------------------------------
   *    Variable Initialization
   *   -------------------------
   */

#ifdef MRFI_ASSERTS_ARE_ON
  PAN_ID0 = 0xFF;
  PAN_ID1 = 0xFF;
#endif



  /* ------------------------------------------------------------------
   *    Initialize Random Seed Value
   *   -------------------------------
   */


  /*
   *  Set radio for infinite reception.  Once radio reaches this state,
   *  it will stay in receive mode regardless RF activity.
   */
  FRMCTRL0 = (FRMCTRL0 & ~RX_MODE_MASK) | RX_MODE_INFINITE_RX;

  /* turn on the receiver */
  RFST = ISRXON;

  /* Wait for RSSI to be valid. Once valid, radio is stable and random bits
   * can be read.
   */
  MRFI_RSSI_VALID_WAIT();

  /* put 16 random bits into the seed value */
  {
    uint16_t rndSeed;
    uint8_t  i;

    rndSeed = 0;

    for(i=0; i<16; i++)
    {
      /* read random bit to populate the random seed */
      rndSeed = (rndSeed << 1) | (RFRND & 0x01);
    }

    /*
     *  The seed value must not be zero.  If it is, the pseudo random sequence will be always be zero.
     *  There is an extremely small chance this seed could randomly be zero (more likely some type of
     *  hardware problem would cause this).  To solve this, a single bit is forced to be one.  This
     *  slightly reduces the randomness but guarantees a good seed value.
     */
    rndSeed |= 0x0080;

    /*
     *  Two writes to RNDL will set the random seed.  A write to RNDL copies current contents
     *  of RNDL to RNDH before writing new the value to RNDL.
     */
    RNDL = rndSeed & 0xFF;
    RNDL = rndSeed >> 8;
  }

  /* turn off the receiver, flush RX FIFO just in case something got in there */
  RFST = ISRFOFF;

  /* flush the rx buffer */
  MRFI_RADIO_FLUSH_RX_BUFFER();

  /* take receiver out of infinite reception mode; set back to normal operation */
  FRMCTRL0 = (FRMCTRL0 & ~RX_MODE_MASK) | RX_MODE_NORMAL;


  /* Initial radio state is OFF state */
  mrfiRadioState = MRFI_RADIO_STATE_OFF;

  /* ------------------------------------------------------------------
   *    Configure Radio Registers
   *   ---------------------------
   */

  /* disable address filtering */
  FRMFILT0 &= ~FRAME_FILTER_EN;

  /* reject beacon/ack/cmd frames and accept only data frames,
   * when filtering is enabled.
   */
  FRMFILT1 &= ~(ACCEPT_BEACON | ACCEPT_ACK | ACCEPT_CMD);

  /* don't enable rx after tx is done. */
  FRMCTRL1 &= ~RX_ENABLE_ON_TX;

  /* set FIFOP threshold to maximum */
  FIFOPCTRL = 127;

  /* set default channel */
  MRFI_SetLogicalChannel( 0 );

  /* set default output power level */
  MRFI_SetRFPwr(MRFI_NUM_POWER_SETTINGS - 1);

  /* enable general RF interrupts */
  IEN2 |= RFIE;


  /* ------------------------------------------------------------------
   *    Final Initialization
   *   -----------------------
   */


  /**********************************************************************************
   *                            Compute reply delay scalar
   *
   * The IEEE radio has a fixed data rate of 250 Kbps. Data rate inference
   * from radio regsiters is not necessary for this radio.
   *
   * The maximum delay needed depends on the MAX_APP_PAYLOAD parameter. Figure
   * out how many bits that will be when overhead is included. Bits/bits-per-second
   * is seconds to transmit (or receive) the maximum frame. We multiply this number
   * by 1000 to find the time in milliseconds. We then additionally multiply by
   * 10 so we can add 5 and divide by 10 later, thus rounding up to the number of
   * milliseconds. This last won't matter for slow transmissions but for faster ones
   * we want to err on the side of being conservative and making sure the radio is on
   * to receive the reply. The semaphore monitor will shut it down. The delay adds in
   * a platform fudge factor that includes processing time on peer plus lags in Rx and
   * processing time on receiver's side. Also includes round trip delays from CCA
   * retries. This portion is included in PLATFORM_FACTOR_CONSTANT defined in mrfi.h.
   *
   * **********************************************************************************
   */

#define   PHY_PREAMBLE_SYNC_BYTES    8

  {
    uint32_t bits, dataRate = 250000;

    bits = ((uint32_t)((PHY_PREAMBLE_SYNC_BYTES + MRFI_MAX_FRAME_SIZE)*8))*10000;

    /* processing on the peer + the Tx/Rx time plus more */
    sReplyDelayScalar = PLATFORM_FACTOR_CONSTANT + (((bits/dataRate)+5)/10);
  }

  /*
   *  Random delay - This prevents devices on the same power source from repeated
   *  transmit collisions on power up.
   */
  Mrfi_RandomBackoffDelay();

  /* enable global interrupts */
  BSP_ENABLE_INTERRUPTS();
}
예제 #4
0
/**************************************************************************************************
 * @fn          MRFI_Transmit
 *
 * @brief       Transmit a packet using CCA algorithm.
 *
 * @param       pPacket - pointer to packet to transmit
 *
 * @return      Return code indicates success or failure of transmit:
 *                  MRFI_TX_RESULT_SUCCESS - transmit succeeded
 *                  MRFI_TX_RESULT_FAILED  - transmit failed because CCA failed
 **************************************************************************************************
 */
uint8_t MRFI_Transmit(mrfiPacket_t * pPacket, uint8_t txType)
{
  static uint8_t dsn = 0;
  uint8_t txResult = MRFI_TX_RESULT_SUCCESS;

  /* radio must be awake to transmit */
  MRFI_ASSERT( mrfiRadioState != MRFI_RADIO_STATE_OFF );


  /* ------------------------------------------------------------------
   *    Initialize hardware for transmit
   *   -----------------------------------
   */

  /* turn off reciever */
  Mrfi_RxModeOff();

  /* clear 'transmit done' interrupt flag, this bit is tested to see when transmit completes */
  RFIRQF1 &= ~IRQ_TXDONE;


  /* ------------------------------------------------------------------
   *    Populate the IEEE fields in frame
   *   ------------------------------------
   */

  /* set the sequence number, also known as DSN (Data Sequence Number) */
  pPacket->frame[MRFI_DSN_OFFSET] = dsn;

  /* increment the sequence number, value is retained (static variable) for use in next transmit */
  dsn++;

  /*
   *  Populate the FCF (Frame Control Field) with the following settings.
   *
   *    bits    description                         setting
   *  --------------------------------------------------------------------------------------
   *      0-2   Frame Type                          001 - data frame
   *        3   Security Enabled                      0 - security disabled
   *        4   Frame Pending                         0 - no pending data
   *        5   Ack Request                           0 - no Ack request
   *        6   PAN ID Compression                    0 - no PAN ID compression
   *        7   Reserved                              0 - reserved
   *  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   *      8-9   Reserved                             00 - reserved
   *    10-11   Destination Addressing Mode          10 - PAN ID + 16-bit short address
   *    12-13   Frame Version                        00 - IEEE Std 802.15.4-2003
   *    14-15   Source Addressing Mode               10 - PAN ID + 16-bit short address
   *
   */
  pPacket->frame[MRFI_FCF_OFFSET]   = MRFI_FCF_0_7;
  pPacket->frame[MRFI_FCF_OFFSET+1] = MRFI_FCF_8_15;


  /* ------------------------------------------------------------------
   *    Write packet to transmit FIFO
   *   --------------------------------
   */
  {
    uint8_t txBufLen;
    uint8_t * p;
    uint8_t i;

    /* flush FIFO of any previous transmit that did not go out */
    RFST = ISFLUSHTX;

    /* set point at beginning of outgoing frame */
    p = &pPacket->frame[MRFI_LENGTH_FIELD_OFFSET];

    /* get number of bytes in the packet (does not include the length byte) */
    txBufLen = *p;

    /*
     *  Write the length byte to the FIFO.  This length does *not* include the length field
     *  itself but does include the size of the FCS (generically known as RX metrics) which
     *  is generated automatically by the radio.
     */
    RFD = txBufLen + MRFI_RX_METRICS_SIZE;

    /* write packet bytes to FIFO */
    for (i=0; i<txBufLen; i++)
    {
      p++;
      RFD = *p;
    }
  }

  /* ------------------------------------------------------------------
   *    Immediate transmit
   *   ---------------------
   */
  if (txType == MRFI_TX_TYPE_FORCED)
  {
    /* strobe transmit */
    RFST = ISTXON;

    /* wait for transmit to complete */
    while (!(RFIRQF1 & IRQ_TXDONE));

    /* transmit is done */
  }
  else
  {
    /* ------------------------------------------------------------------
     *    CCA transmit
     *   ---------------
     */
    MRFI_ASSERT( txType == MRFI_TX_TYPE_CCA );

    {
      bspIState_t s;
      uint8_t txActive;
      uint8_t ccaRetries;

      /* set number of CCA retries */
      ccaRetries = MRFI_CCA_RETRIES;


      /* ===============================================================================
       *    CCA Algorithm Loop
       *   ====================
       */
      for (;;)
      {
        /* Turn ON the receiver to perform CCA. Can not call Mrfi_RxModeOn(),
         * since that will enable the rx interrupt, which we do not want.
         */
        RFST = ISRXON;

        /*
         *  Wait for CCA to be valid.
         */
        MRFI_RSSI_VALID_WAIT();

        /*
         *  Initiate transmit with CCA.  Command is strobed and then status is
         *  immediately checked.  If status shows transmit is active, this means
         *  that CCA passed and the transmit has gone out.  A critical section
         *  guarantees timing status check happens immediately after strobe.
         */
        BSP_ENTER_CRITICAL_SECTION(s);
        RFST = ISTXONCCA;
        txActive = FSMSTAT1 & SAMPLED_CCA;
        BSP_EXIT_CRITICAL_SECTION(s);

        /* see transmit went out */
        if (txActive)
        {
          /* ----------|  CCA Passed |---------- */

          /* wait for transmit to complete */
          while (!(RFIRQF1 & IRQ_TXDONE));

          /* transmit is done. break out of CCA algorithm loop */
          break;
        }
        else
        {
          /* ----------|  CCA Failed |---------- */

          /* if no CCA retries are left, transmit failed so abort */
          if (ccaRetries == 0)
          {
            /* set return value for failed transmit */
            txResult = MRFI_TX_RESULT_FAILED;

            /* break out of CCA algorithm loop */
            break;
          }

          /* decrement CCA retries before loop continues */
          ccaRetries--;

          /* turn off reciever to conserve power during backoff */
          Mrfi_RxModeOff();

          /* delay for a random number of backoffs */
          Mrfi_RandomBackoffDelay();
        }
      }
      /*
       *  ---  end CCA Algorithm Loop ---
       * =============================================================================== */
    }
  }


  /* turn radio back off to put it in a known state */
  Mrfi_RxModeOff();

  /* If the radio was in RX state when transmit was attempted,
   * put it back in RX state.
   */
  if(mrfiRadioState == MRFI_RADIO_STATE_RX)
  {
    Mrfi_RxModeOn();
  }

  /* return the result of the transmit */
  return( txResult );
}
예제 #5
0
/**************************************************************************************************
 * @fn          MRFI_Init
 *
 * @brief       Initialize MRFI.
 *
 * @param       none
 *
 * @return      none
 **************************************************************************************************
 */
void MRFI_Init(void)
{
  /* ------------------------------------------------------------------
   *    Run-time integrity checks
   *   ---------------------------
   */

  /* verify the correct radio is installed */
  MRFI_ASSERT( CHIPID == MRFI_RADIO_PARTNUM );      /* wrong radio */
  MRFI_ASSERT( CHVER  >= MRFI_RADIO_MIN_VERSION );  /* obsolete radio version */

  /* ------------------------------------------------------------------
   *    Configure IO ports
   *   ---------------------------
   */

#if defined(MRFI_PA_LNA_ENABLED) && defined(BSP_BOARD_SRF04EB)
  MRFI_BOARD_PA_LNA_CONFIG_PORTS();
  MRFI_BOARD_PA_LNA_HGM();
#endif


  /* ------------------------------------------------------------------
   *    Configure clock to use XOSC
   *   -----------------------------
   */
  SLEEP &= ~OSC_PD;                       /* turn on 16MHz RC and 32MHz XOSC */
  while (!(SLEEP & XOSC_STB));            /* wait for 32MHz XOSC stable */
  asm("NOP");                             /* chip bug workaround */
  {
    uint16_t i;

    /* Require 63us delay for all revs */
    for (i=0; i<504; i++)
    {
      asm("NOP");
    }
  }
  CLKCON = (0x00 | OSC_32KHZ);            /* 32MHz XOSC */
  while (CLKCON != (0x00 | OSC_32KHZ));
  SLEEP |= OSC_PD;                        /* turn off 16MHz RC */


  /* ------------------------------------------------------------------
   *    Variable Initialization
   *   -------------------------
   */

#ifdef MRFI_ASSERTS_ARE_ON
  PANIDL = 0xFF;
  PANIDH = 0xFF;
#endif


  /* ------------------------------------------------------------------
   *    Initialize Random Seed Value
   *   -------------------------------
   */

  /* turn on radio power, pend for the power-up delay */
  RFPWR &= ~RREG_RADIO_PD;
  while((RFPWR & ADI_RADIO_PD));

  /*
   *  Set radio for infinite reception.  Once radio reaches this state,
   *  it will stay in receive mode regardless RF activity.
   */
  MDMCTRL1L = MDMCTRL1L_RESET_VALUE | RX_MODE_INFINITE_RECEPTION;

  /* turn on the receiver */
  RFST = ISRXON;

  /*
   *  Wait for radio to reach infinite reception state.  Once it does,
   *  The least significant bit of ADTSTH should be pretty random.
   */
  while (FSMSTATE != FSM_FFCTRL_STATE_RX_INF)

  /* put 16 random bits into the seed value */
  {
    uint16_t rndSeed;
    uint8_t  i;

    rndSeed = 0;

    for(i=0; i<16; i++)
    {
      /* use most random bit of analog to digital receive conversion to populate the random seed */
      rndSeed = (rndSeed << 1) | (ADCTSTH & 0x01);
    }

    /*
     *  The seed value must not be zero.  If it is, the pseudo random sequence will be always be zero.
     *  There is an extremely small chance this seed could randomly be zero (more likely some type of
     *  hardware problem would cause this).  To solve this, a single bit is forced to be one.  This
     *  slightly reduces the randomness but guarantees a good seed value.
     */
    rndSeed |= 0x0080;

    /*
     *  Two writes to RNDL will set the random seed.  A write to RNDL copies current contents
     *  of RNDL to RNDH before writing new the value to RNDL.
     */
    RNDL = rndSeed & 0xFF;
    RNDL = rndSeed >> 8;
  }

  /* turn off the receiver, flush RX FIFO just in case something got in there */
  RFST = ISRFOFF;

  /* flush the rx buffer */
  MRFI_RADIO_FLUSH_RX_BUFFER();

  /* take receiver out of infinite reception mode; set back to normal operation */
  MDMCTRL1L = MDMCTRL1L_RESET_VALUE | RX_MODE_NORMAL_OPERATION;

  /* turn radio back off */
  RFPWR |= RREG_RADIO_PD;

  /* Initial radio state is OFF state */
  mrfiRadioState = MRFI_RADIO_STATE_OFF;
  /* ------------------------------------------------------------------
   *    Configure Radio Registers
   *   ---------------------------
   */

  /* tuning adjustments for optimal radio performance; details available in datasheet */
  RXCTRL0H = 0x32;
  RXCTRL0L = 0xF5;

  /* disable address filtering */
  MDMCTRL0H &= ~ADDR_DECODE;

  /* set FIFOP threshold to maximum */
  IOCFG0 = 127;

  /* set default channel */
  MRFI_SetLogicalChannel( 0 );

  /* enable general RF interrupts */
  IEN2 |= RFIE;


  /* ------------------------------------------------------------------
   *    Final Initialization
   *   -----------------------
   */


  /**********************************************************************************
   *                            Compute reply delay scalar
   *
   * The IEEE radio has a fixed data rate of 250 Kbps. Data rate inference
   * from radio regsiters is not necessary for this radio.
   *
   * The maximum delay needed depends on the MAX_APP_PAYLOAD parameter. Figure
   * out how many bits that will be when overhead is included. Bits/bits-per-second
   * is seconds to transmit (or receive) the maximum frame. We multiply this number
   * by 1000 to find the time in milliseconds. We then additionally multiply by
   * 10 so we can add 5 and divide by 10 later, thus rounding up to the number of
   * milliseconds. This last won't matter for slow transmissions but for faster ones
   * we want to err on the side of being conservative and making sure the radio is on
   * to receive the reply. The semaphore monitor will shut it down. The delay adds in
   * a fudge factor that includes processing time on peer plus lags in Rx and processing
   * time on receiver's side.
   *
   * **********************************************************************************
   */
#define   PLATFORM_FACTOR_CONSTANT    2
#define   PHY_PREAMBLE_SYNC_BYTES     8

  {
    uint32_t bits, dataRate = 250000;

    bits = ((uint32_t)((PHY_PREAMBLE_SYNC_BYTES + MRFI_MAX_FRAME_SIZE)*8))*10000;

    /* processing on the peer + the Tx/Rx time plus more */
    sReplyDelayScalar = PLATFORM_FACTOR_CONSTANT + (((bits/dataRate)+5)/10);
  }

  /*
   *  Random delay - This prevents devices on the same power source from repeated
   *  transmit collisions on power up.
   */
  Mrfi_RandomBackoffDelay();

  /* enable global interrupts */
  BSP_ENABLE_INTERRUPTS();
}