/**
* \brief Starts the timer for the backoff period and enables receiver.
*/
static void start_backoff(void)
{
/* Start backoff timer to trigger CCA */
uint8_t backoff_8;
backoff_8 = (uint8_t)rand() & ((1 << BE) - 1);
if (backoff_8 > 0) {
uint16_t backoff_16;
uint32_t backoff_duration_us;
backoff_16 = backoff_8 * aUnitBackoffPeriod;
backoff_duration_us = TAL_CONVERT_SYMBOLS_TO_US(backoff_16);
pal_timer_start(TAL_T_BOFF, backoff_duration_us,
TIMEOUT_RELATIVE,
(FUNC_PTR)cca_start, NULL);
tal_state = TAL_BACKOFF;
#ifdef RX_WHILE_BACKOFF
/* Switch receiver on during backoff */
if (NULL == tal_rx_buffer) {
set_trx_state(CMD_PLL_ON);
tal_rx_on_required = true;
} else {
set_trx_state(CMD_RX_AACK_ON); /* receive while backoff
**/
}
#else
set_trx_state(CMD_PLL_ON);
#endif
} else {
/* Start CCA immediately - no backoff */
cca_start(NULL);
}
}
/**
* @brief Starts the timer for the backoff period and enables receiver.
*
* @param trx_id Transceiver identifier
*/
static void start_backoff(trx_id_t trx_id)
{
/* Start backoff timer to trigger CCA */
uint8_t backoff_8;
backoff_8 = (uint8_t)(rand() & (((uint16_t)1 << BE[trx_id]) - 1));
if (backoff_8 > 0) {
uint8_t timer_id;
uint16_t backoff_16;
uint32_t backoff_duration_us;
backoff_16 = backoff_8 * aUnitBackoffPeriod;
backoff_duration_us
= (uint32_t)tal_pib[trx_id].SymbolDuration_us *
(uint32_t)backoff_16;
#ifdef REDUCED_BACKOFF_DURATION
backoff_duration_us = REDUCED_BACKOFF_DURATION;
#endif
if (trx_id == RF09) {
timer_id = TAL_T_0;
} else {
timer_id = TAL_T_1;
}
retval_t status
= pal_timer_start(timer_id, backoff_duration_us,
TIMEOUT_RELATIVE,
(FUNC_PTR)cca_start,
(void *)&timer_cb_parameter[trx_id]);
if (status != MAC_SUCCESS) {
tx_done_handling(trx_id, status);
return;
}
tx_state[trx_id] = TX_BACKOFF;
#ifdef RX_WHILE_BACKOFF
/* Keep receiver on during backoff */
if ((trx_default_state[trx_id] == RF_RX) &&
(tal_pib[trx_id].NumRxFramesDuringBackoff <
tal_pib[trx_id].MaxNumRxFramesDuringBackoff)) {
if (trx_state[trx_id] != RF_RX) {
if (trx_state[trx_id] == RF_TRXOFF) {
switch_to_txprep(trx_id);
}
switch_to_rx(trx_id);
}
} else
#endif
{
#ifdef USE_TXPREP_DURING_BACKOFF
/* Switch to TXPREP during backoff */
if (trx_state[trx_id] != RF_TXPREP) {
switch_to_txprep(trx_id);
}
#else
/* Switch to TRXOFF during backoff */
if (trx_state[trx_id] != RF_TRXOFF) {
uint16_t reg_offset = RF_BASE_ADDR_OFFSET *
trx_id;
trx_reg_write(reg_offset + RG_RF09_CMD,
RF_TRXOFF);
trx_state[trx_id] = RF_TRXOFF;
}
#endif
}
} else { /* no backoff required */
/* Start CCA immediately - no backoff */
cca_start((void *)&timer_cb_parameter[trx_id]);
}
}
