/**************************************************************************************************
* @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_TRANSMIT_SUCCESS - transmit succeeded
* MRFI_TRANSMIT_CCA_FAILED - transmit failed because of CCA check(s)
* MRFI_TRANSMIT_RADIO_ASLEEP - transmit failed because radio was asleep
**************************************************************************************************
*/
uint8_t MRFI_Transmit(mrfiPacket_t * pPacket)
{
uint8_t ccaRetries;
uint8_t txBufLen;
uint8_t savedSyncIntState;
uint8_t returnValue;
/* abort transmit if radio is asleep */
{
bspIState_t s;
/* critical section necessary for watertight testing and setting of state variables */
BSP_ENTER_CRITICAL_SECTION(s);
/* if radio is asleep, abort transmit and return reason for failure */
if (mrfiRadioIsSleeping)
{
BSP_EXIT_CRITICAL_SECTION(s);
return( MRFI_TRANSMIT_RADIO_ASLEEP );
}
/* radio is not asleep, set flag that indicates transmit is active */
mrfiTxActive = 1;
BSP_EXIT_CRITICAL_SECTION(s);
}
/* set number of CCA retries */
ccaRetries = MRFI_CCA_RETRIES;
/* compute number of bytes to write to transmit FIFO */
txBufLen = pPacket->frame[MRFI_LENGTH_FIELD_OFS] + MRFI_LENGTH_FIELD_SIZE;
/* write packet to transmit FIFO */
mrfiSpiWriteTxFifo(&(pPacket->frame[0]), txBufLen);
/* ===============================================================================
* Main Loop
* =============
*/
for (;;)
{
/* CCA delay */
MRFI_DELAY(2000);
/* disable sync pin interrupts, necessary because both transmit and receive affect sync signal */
MRFI_DISABLE_SYNC_PIN_INT();
/* store the sync pin interrupt flag, important so original state can be restored */
savedSyncIntState = MRFI_SYNC_PIN_INT_FLAG_IS_SET();
/*
* 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();
/* send strobe to initiate transmit */
mrfiSpiCmdStrobe(MRFI_CC2500_SPI_STROBE_STX);
/* delay long enough for the PA_PD signal to indicate a successful transmit */
MRFI_DELAY(250);
/* if the interrupt flag of the PA_PD pin is set, CCA passed and the transmit has started */
if (MRFI_PAPD_INT_FLAG_IS_SET())
{
/* ------------------------------------------------------------------
* Clear Channel Assessment passed.
* ----------------------------------
*/
/* wait for transmit to complete */
while (!MRFI_PAPD_PIN_IS_HIGH());
/*
* Restore the original sync interrupt state. The successful transmit just
* caused a transition on the sync signal that set the flag (if not already
* set). To restore the original state, the flag is simply cleared if it
* was clear earlier.
*/
if (!savedSyncIntState)
{
MRFI_CLEAR_SYNC_PIN_INT_FLAG();
}
/* transmit complete, enable sync pin interrupts */
MRFI_ENABLE_SYNC_PIN_INT();
/* set return value for successful transmit and break */
returnValue = MRFI_TRANSMIT_SUCCESS;
break;
}
/* ------------------------------------------------------------------
* Clear Channel Assessment failed.
* ----------------------------------
*/
/* CCA failed, safe to enable sync pin interrupts */
MRFI_ENABLE_SYNC_PIN_INT();
/* if no CCA retries are left, transmit failed so abort */
if (ccaRetries == 0)
{
bspIState_t s;
/*
* Flush the transmit FIFO. It must be flushed so that
* the next transmit can start with a clean slate.
* Critical section prevents receive interrupt from
* occurring in the middle of clean-up.
*/
BSP_ENTER_CRITICAL_SECTION(s);
mrfiSpiCmdStrobe(MRFI_CC2500_SPI_STROBE_SIDLE);
mrfiSpiCmdStrobe(MRFI_CC2500_SPI_STROBE_SFTX);
mrfiSpiCmdStrobe(MRFI_CC2500_SPI_STROBE_SRX);
BSP_EXIT_CRITICAL_SECTION(s);
/* set return value for failed transmit and break */
returnValue = MRFI_TRANSMIT_CCA_FAILED;
break;
}
/* decrement CCA retries before loop continues */
ccaRetries--;
}
/*
* =============================================================================== */
mrfiTxActive = 0;
return( returnValue );
}
