/**************************************************************************************************
* @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 );
}
/**************************************************************************************************
* @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 );
}
