/*
* \brief Starts slotted CSMA
*/
bool slotted_csma_start(bool perform_frame_retry)
{
PIN_CSMA_START(); /* debug pin to switch on: define ENABLE_DEBUG_PINS,
* pal_config.h */
bool return_val = false; /* Assume error case */
if (check_beacon_reception()) {
tal_state = TAL_SLOTTED_CSMA;
csma_param_init();
if (perform_frame_retry) {
number_of_tx_retries = 0;
} else {
/* Use the max value to indicate that no retries are
* required. */
number_of_tx_retries = tal_pib.MaxFrameRetries;
}
calculate_transaction_duration();
/* Get a random backoff period duration. */
remaining_backoff_periods = (uint8_t)(rand() & ((1 << BE) - 1));
csma_backoff_calculation();
return_val = true;
}
return return_val;
}
/**
* @brief Starts slotted CSMA
*/
void slotted_csma_start(bool perform_frame_retry)
{
PIN_CSMA_START(); // debug pin to switch on: define ENABLE_DEBUG_PINS, pal_config.h
tal_state = TAL_SLOTTED_CSMA;
if (check_beacon_reception() == false)
{
tal_csma_state = NO_BEACON_TRACKING;
return;
}
csma_param_init();
if (perform_frame_retry)
{
number_of_tx_retries = 0;
}
else
{
// use the max value to indicate that no retries are required
number_of_tx_retries = tal_pib_MaxFrameRetries;
}
calculate_transaction_duration();
/* Get a random backoff period duration. */
remaining_backoff_periods = (uint8_t)(rand() & ((1 << BE) - 1));
csma_backoff_calculation();
}
/*
* \brief Requests to TAL to transmit frame
*
* This function is called by the MAC to deliver a frame to the TAL
* to be transmitted by the transceiver.
*
* \param tx_frame Pointer to the frame_info_t structure updated by the MAC
* layer
* \param csma_mode Indicates mode of csma-ca to be performed for this frame
* \param perform_frame_retry Indicates whether to retries are to be performed
* for
* this frame
*
* \return MAC_SUCCESS if the TAL has accepted the data from the MAC for frame
* transmission
* TAL_BUSY if the TAL is busy servicing the previous MAC request
*/
retval_t tal_tx_frame(frame_info_t *tx_frame, csma_mode_t csma_mode,
bool perform_frame_retry)
{
if (tal_state != TAL_IDLE) {
return TAL_BUSY;
}
/*
* Store the pointer to the provided frame structure.
* This is needed for the callback function.
*/
mac_frame_ptr = tx_frame;
/* Set pointer to actual mpdu to be downloaded to the transceiver. */
tal_frame_to_tx = tx_frame->mpdu;
last_frame_length = tal_frame_to_tx[0] - 1;
/*
* In case the frame is too large, return immediately indicating
* invalid status.
*/
if (tal_frame_to_tx == NULL) {
return MAC_INVALID_PARAMETER;
}
#ifdef BEACON_SUPPORT
/* Check if beacon mode is used */
if (csma_mode == CSMA_SLOTTED) {
if (!slotted_csma_start(perform_frame_retry)) {
return MAC_CHANNEL_ACCESS_FAILURE;
}
} else {
#if (MAC_INDIRECT_DATA_FFD == 1)
/*
* Check if frame is using indirect transmission, but do not use
* the
* indirect_in_transit flag. This flag is not set for null data
* frames.
*/
if ((tal_pib.BeaconOrder < NON_BEACON_NWK) &&
(csma_mode == NO_CSMA_WITH_IFS) &&
(perform_frame_retry == false)) {
/*
* Check if indirect transmission can be completed
* before the next
* beacon transmission.
*/
uint32_t time_between_beacons_sym;
uint32_t next_beacon_time_sym;
uint32_t now_time_sym;
uint32_t duration_before_beacon_sym;
/* Calculate the entire transaction duration. Re-use
* function of slotted CSMA.
* The additional two backoff periods used for CCA are
* kept as a guard time.
*/
calculate_transaction_duration();
/* Calculate the duration until the next beacon needs to
* be transmitted. */
time_between_beacons_sym = TAL_GET_BEACON_INTERVAL_TIME(
tal_pib.BeaconOrder);
next_beacon_time_sym = tal_add_time_symbols(
tal_pib.BeaconTxTime,
time_between_beacons_sym);
pal_get_current_time(&now_time_sym);
now_time_sym = TAL_CONVERT_US_TO_SYMBOLS(now_time_sym);
duration_before_beacon_sym = tal_sub_time_symbols(
next_beacon_time_sym, now_time_sym);
/* Check if transaction can be completed before next
* beacon transmission. */
if ((now_time_sym >= next_beacon_time_sym) ||
((transaction_duration_periods *
aUnitBackoffPeriod) >
duration_before_beacon_sym)) {
/*
* Transaction will not be completed before next
* beacon transmission.
* Therefore the transmission is not executed.
*/
return MAC_CHANNEL_ACCESS_FAILURE;
}
}
#endif /* #if (MAC_INDIRECT_DATA_FFD == 1) */
send_frame(csma_mode, perform_frame_retry);
}
#else /* No BEACON_SUPPORT */
send_frame(csma_mode, perform_frame_retry);
#endif /* BEACON_SUPPORT / No BEACON_SUPPORT */
return MAC_SUCCESS;
}
