| /* Copyright (c) 2017 - 2018, Nordic Semiconductor ASA |
| * All rights reserved. |
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| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are met: |
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| * list of conditions and the following disclaimer. |
| * |
| * 2. Redistributions in binary form must reproduce the above copyright notice, |
| * this list of conditions and the following disclaimer in the documentation |
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| * |
| * 3. Neither the name of Nordic Semiconductor ASA nor the names of its |
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| * this software without specific prior written permission. |
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| */ |
| |
| /** |
| * @file |
| * This file implements CSMA-CA procedure for the 802.15.4 driver. |
| * |
| */ |
| |
| #include "nrf_802154_csma_ca.h" |
| |
| #include <assert.h> |
| #include <stdbool.h> |
| #include <stdint.h> |
| #include <stdlib.h> |
| |
| #include "nrf_802154_config.h" |
| #include "nrf_802154_const.h" |
| #include "nrf_802154_debug.h" |
| #include "nrf_802154_notification.h" |
| #include "nrf_802154_request.h" |
| #include "timer_scheduler/nrf_802154_timer_sched.h" |
| |
| #if NRF_802154_CSMA_CA_ENABLED |
| |
| static uint8_t m_nb; ///< The number of times the CSMA-CA algorithm was required to back off while attempting the current transmission. |
| static uint8_t m_be; ///< Backoff exponent, which is related to how many backoff periods a device shall wait before attempting to assess a channel. |
| |
| static const uint8_t * mp_psdu; ///< Pointer to PSDU of the frame being transmitted. |
| static nrf_802154_timer_t m_timer; ///< Timer used to back off during CSMA-CA procedure. |
| static bool m_is_running; ///< Indicates if CSMA-CA procedure is running. |
| |
| /** |
| * @brief Perform appropriate actions for busy channel conditions. |
| * |
| * According to CSMA-CA description in 802.15.4 specification, when channel is busy NB and BE shall |
| * be incremented and the device shall wait random delay before next CCA procedure. If NB reaches |
| * macMaxCsmaBackoffs procedure fails. |
| * |
| * @retval true Procedure failed and TX failure should be notified to the next higher layer. |
| * @retval false Procedure is still ongoing and TX failure should be handled internally. |
| */ |
| static bool channel_busy(void); |
| |
| /** |
| * @brief Check if CSMA-CA is ongoing. |
| * |
| * @retval true CSMA-CA is running. |
| * @retval false CSMA-CA is not running currently. |
| */ |
| static bool procedure_is_running(void) |
| { |
| return m_is_running; |
| } |
| |
| /** |
| * @brief Stop CSMA-CA procedure. |
| */ |
| static void procedure_stop(void) |
| { |
| m_is_running = false; |
| } |
| |
| /** |
| * Notify MAC layer that channel is busy if tx request failed and there are no retries left. |
| * |
| * @param[in] result Result of TX request. |
| */ |
| static void notify_busy_channel(bool result) |
| { |
| if (!result && (m_nb >= (NRF_802154_CSMA_CA_MAX_CSMA_BACKOFFS - 1))) |
| { |
| nrf_802154_notify_transmit_failed(mp_psdu, NRF_802154_TX_ERROR_BUSY_CHANNEL); |
| } |
| } |
| |
| /** |
| * @brief Perform CCA procedure followed by frame transmission. |
| * |
| * If transmission is requested, CSMA-CA module waits for notification from the FSM module. |
| * If transmission request fails, CSMA-CA module performs procedure for busy channel condition |
| * @sa channel_busy(). |
| * |
| * @param[in] p_context Unused variable passed from the Timer Scheduler module. |
| */ |
| static void frame_transmit(void * p_context) |
| { |
| (void)p_context; |
| |
| nrf_802154_log(EVENT_TRACE_ENTER, FUNCTION_CSMA_FRAME_TRANSMIT); |
| |
| if (procedure_is_running()) |
| { |
| if (!nrf_802154_request_transmit(NRF_802154_TERM_NONE, |
| REQ_ORIG_CSMA_CA, |
| mp_psdu, |
| true, |
| true, |
| notify_busy_channel)) |
| { |
| (void)channel_busy(); |
| } |
| } |
| |
| nrf_802154_log(EVENT_TRACE_EXIT, FUNCTION_CSMA_FRAME_TRANSMIT); |
| } |
| |
| /** |
| * @brief Delay CCA procedure for random (2^BE - 1) unit backoff periods. |
| */ |
| static void random_backoff_start(void) |
| { |
| uint8_t backoff_periods = rand() % (1 << m_be); |
| |
| m_timer.callback = frame_transmit; |
| m_timer.p_context = NULL; |
| m_timer.t0 = nrf_802154_timer_sched_time_get(); |
| m_timer.dt = backoff_periods * UNIT_BACKOFF_PERIOD; |
| |
| nrf_802154_timer_sched_add(&m_timer, false); |
| } |
| |
| static bool channel_busy(void) |
| { |
| bool result = true; |
| |
| if (procedure_is_running()) |
| { |
| nrf_802154_log(EVENT_TRACE_ENTER, FUNCTION_CSMA_CHANNEL_BUSY); |
| |
| m_nb++; |
| |
| if (m_be < NRF_802154_CSMA_CA_MAX_BE) |
| { |
| m_be++; |
| } |
| |
| if (m_nb < NRF_802154_CSMA_CA_MAX_CSMA_BACKOFFS) |
| { |
| random_backoff_start(); |
| result = false; |
| } |
| else |
| { |
| procedure_stop(); |
| } |
| |
| nrf_802154_log(EVENT_TRACE_EXIT, FUNCTION_CSMA_CHANNEL_BUSY); |
| } |
| |
| return result; |
| } |
| |
| void nrf_802154_csma_ca_start(const uint8_t * p_data) |
| { |
| assert(!procedure_is_running()); |
| |
| mp_psdu = p_data; |
| m_nb = 0; |
| m_be = NRF_802154_CSMA_CA_MIN_BE; |
| m_is_running = true; |
| |
| random_backoff_start(); |
| } |
| |
| bool nrf_802154_csma_ca_abort(nrf_802154_term_t term_lvl, req_originator_t req_orig) |
| { |
| bool result = false; |
| |
| // Stop CSMA-CA only if request by the core or the higher layer. |
| if ((req_orig != REQ_ORIG_CORE) && (req_orig != REQ_ORIG_HIGHER_LAYER)) |
| { |
| return true; |
| } |
| |
| nrf_802154_log(EVENT_TRACE_ENTER, FUNCTION_CSMA_ABORT); |
| |
| if (term_lvl >= NRF_802154_TERM_802154) |
| { |
| // Stop CSMA-CA if termination level is high enough. |
| nrf_802154_timer_sched_remove(&m_timer); |
| procedure_stop(); |
| |
| result = true; |
| } |
| else if (!procedure_is_running()) |
| { |
| // Return success in case procedure is already stopped. |
| result = true; |
| } |
| |
| nrf_802154_log(EVENT_TRACE_EXIT, FUNCTION_CSMA_ABORT); |
| |
| return result; |
| } |
| |
| bool nrf_802154_csma_ca_tx_failed_hook(const uint8_t * p_frame, nrf_802154_tx_error_t error) |
| { |
| (void)error; |
| |
| bool result = true; |
| |
| if (p_frame == mp_psdu) |
| { |
| nrf_802154_log(EVENT_TRACE_ENTER, FUNCTION_CSMA_TX_FAILED); |
| |
| result = channel_busy(); |
| |
| nrf_802154_log(EVENT_TRACE_EXIT, FUNCTION_CSMA_TX_FAILED); |
| } |
| |
| return result; |
| } |
| |
| bool nrf_802154_csma_ca_tx_started_hook(const uint8_t * p_frame) |
| { |
| if (p_frame == mp_psdu) |
| { |
| nrf_802154_log(EVENT_TRACE_ENTER, FUNCTION_CSMA_TX_STARTED); |
| |
| assert(!nrf_802154_timer_sched_is_running(&m_timer)); |
| procedure_stop(); |
| |
| nrf_802154_log(EVENT_TRACE_EXIT, FUNCTION_CSMA_TX_STARTED); |
| } |
| |
| return true; |
| } |
| |
| #endif // NRF_802154_CSMA_CA_ENABLED |