Steve Kim
mbed library sources(for async_print)
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mbed official
Revision 495:01cb89f68337, committed 2015-03-20
- Comitter:
- mbed_official
- Date:
- Fri Mar 20 09:30:08 2015 +0000
- Parent:
- 494:41cd0bfadcd0
- Child:
- 496:543871686697
- Commit message:
- Synchronized with git revision d1d900d30c656b1f35f4f5db49e47ea199b0b8d6
Full URL: https://github.com/mbedmicro/mbed/commit/d1d900d30c656b1f35f4f5db49e47ea199b0b8d6/
Changed in this revision
--- a/common/us_ticker_api.c Fri Mar 20 09:15:08 2015 +0000
+++ b/common/us_ticker_api.c Fri Mar 20 09:30:08 2015 +0000
@@ -77,6 +77,10 @@
prev = p;
p = p->next;
}
+
+ /* if we're at the end p will be NULL, which is correct */
+ obj->next = p;
+
/* if prev is NULL we're at the head */
if (prev == NULL) {
head = obj;
@@ -84,8 +88,6 @@
} else {
prev->next = obj;
}
- /* if we're at the end p will be NULL, which is correct */
- obj->next = p;
__enable_irq();
}
--- a/targets/hal/TARGET_NORDIC/TARGET_MCU_NRF51822/Lib/app_common/app_timer.c Fri Mar 20 09:15:08 2015 +0000
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,1160 +0,0 @@
-/* Copyright (c) 2012 Nordic Semiconductor. All Rights Reserved.
- *
- * The information contained herein is property of Nordic Semiconductor ASA.
- * Terms and conditions of usage are described in detail in NORDIC
- * SEMICONDUCTOR STANDARD SOFTWARE LICENSE AGREEMENT.
- *
- * Licensees are granted free, non-transferable use of the information. NO
- * WARRANTY of ANY KIND is provided. This heading must NOT be removed from
- * the file.
- *
- */
-
-#include "app_timer.h"
-#include <stdlib.h>
-#include "nrf51.h"
-#include "nrf51_bitfields.h"
-#include "nrf_soc.h"
-#include "app_error.h"
-#include "nrf_delay.h"
-#include "app_util.h"
-#include "app_util_platform.h"
-
-
-#define RTC1_IRQ_PRI APP_IRQ_PRIORITY_LOW /**< Priority of the RTC1 interrupt (used for checking for timeouts and executing timeout handlers). */
-#define SWI0_IRQ_PRI APP_IRQ_PRIORITY_LOW /**< Priority of the SWI0 interrupt (used for updating the timer list). */
-
-// The current design assumes that both interrupt handlers run at the same interrupt level.
-// If this is to be changed, protection must be added to prevent them from interrupting each other
-// (e.g. by using guard/trigger flags).
-STATIC_ASSERT(RTC1_IRQ_PRI == SWI0_IRQ_PRI);
-
-#define APP_HIGH_USER_ID 0 /**< User Id for the Application High "user". */
-#define APP_LOW_USER_ID 1 /**< User Id for the Application Low "user". */
-#define THREAD_MODE_USER_ID 2 /**< User Id for the Thread Mode "user". */
-
-#define RTC_COMPARE_OFFSET_MIN 3 /**< Minimum offset between the current RTC counter value and the Capture Compare register. Although the nRF51 Series User Specification recommends this value to be 2, we use 3 to be safer.*/
-
-#define MAX_RTC_TASKS_DELAY 47 /**< Maximum delay until an RTC task is executed. */
-
-/**@brief Timer allocation state type. */
-typedef enum
-{
- STATE_FREE, /**< The timer node is available. */
- STATE_ALLOCATED /**< The timer node has been allocated. */
-} timer_alloc_state_t;
-
-/**@brief Timer node type. The nodes will be used form a linked list of running timers. */
-typedef struct
-{
- timer_alloc_state_t state; /**< Timer allocation state. */
- app_timer_mode_t mode; /**< Timer mode. */
- uint32_t ticks_to_expire; /**< Number of ticks from previous timer interrupt to timer expiry. */
- uint32_t ticks_at_start; /**< Current RTC counter value when the timer was started. */
- uint32_t ticks_first_interval; /**< Number of ticks in the first timer interval. */
- uint32_t ticks_periodic_interval; /**< Timer period (for repeating timers). */
- bool is_running; /**< True if timer is running, False otherwise. */
- app_timer_timeout_handler_t p_timeout_handler; /**< Pointer to function to be executed when the timer expires. */
- void * p_context; /**< General purpose pointer. Will be passed to the timeout handler when the timer expires. */
- app_timer_id_t next; /**< Id of next timer in list of running timers. */
-} timer_node_t;
-
-STATIC_ASSERT(sizeof(timer_node_t) <= APP_TIMER_NODE_SIZE);
-STATIC_ASSERT(sizeof(timer_node_t) % 4 == 0);
-
-/**@brief Set of available timer operation types. */
-typedef enum
-{
- TIMER_USER_OP_TYPE_NONE, /**< Invalid timer operation type. */
- TIMER_USER_OP_TYPE_START, /**< Timer operation type Start. */
- TIMER_USER_OP_TYPE_STOP, /**< Timer operation type Stop. */
- TIMER_USER_OP_TYPE_STOP_ALL /**< Timer operation type Stop All. */
-} timer_user_op_type_t;
-
-/**@brief Structure describing a timer start operation. */
-typedef struct
-{
- uint32_t ticks_at_start; /**< Current RTC counter value when the timer was started. */
- uint32_t ticks_first_interval; /**< Number of ticks in the first timer interval. */
- uint32_t ticks_periodic_interval; /**< Timer period (for repeating timers). */
- void * p_context; /**< General purpose pointer. Will be passed to the timeout handler when the timer expires. */
-} timer_user_op_start_t;
-
-/**@brief Structure describing a timer operation. */
-typedef struct
-{
- timer_user_op_type_t op_type; /**< Timer operation type. */
- app_timer_id_t timer_id; /**< Id of timer on which the operation is to be performed. */
- union
- {
- timer_user_op_start_t start; /**< Structure describing a timer start operation. */
- } params;
-} timer_user_op_t;
-
-STATIC_ASSERT(sizeof(timer_user_op_t) <= APP_TIMER_USER_OP_SIZE);
-STATIC_ASSERT(sizeof(timer_user_op_t) % 4 == 0);
-
-/**@brief Structure describing a timer user.
- *
- * @details For each user of the timer module, there will be a timer operations queue. This queue
- * will hold timer operations issued by this user until the timer interrupt handler
- * processes these operations. For the current implementation, there will be one user for
- * each interrupt level available to the application (APP_HIGH, APP_LOW and THREAD_MODE),
- * but the module can easily be modified to e.g. have one queue per process when using an
- * RTOS. The purpose of the queues is to be able to have a completely lockless timer
- * implementation.
- */
-typedef struct
-{
- uint8_t first; /**< Index of first entry to have been inserted in the queue (i.e. the next entry to be executed). */
- uint8_t last; /**< Index of last entry to have been inserted in the queue. */
- uint8_t user_op_queue_size; /**< Queue size. */
- timer_user_op_t * p_user_op_queue; /**< Queue buffer. */
-} timer_user_t;
-
-STATIC_ASSERT(sizeof(timer_user_t) == APP_TIMER_USER_SIZE);
-STATIC_ASSERT(sizeof(timer_user_t) % 4 == 0);
-
-/**@brief User id type.
- *
- * @details In the current implementation, this will automatically be generated from the current
- * interrupt level.
- */
-typedef uint32_t timer_user_id_t;
-
-#define CONTEXT_QUEUE_SIZE_MAX (2) /**< Timer internal elapsed ticks queue size. */
-
-static uint8_t m_node_array_size; /**< Size of timer node array. */
-static timer_node_t * mp_nodes = NULL; /**< Array of timer nodes. */
-static uint8_t m_user_array_size; /**< Size of timer user array. */
-static timer_user_t * mp_users; /**< Array of timer users. */
-static app_timer_id_t m_timer_id_head; /**< First timer in list of running timers. */
-static uint32_t m_ticks_latest; /**< Last known RTC counter value. */
-static uint32_t m_ticks_elapsed[CONTEXT_QUEUE_SIZE_MAX]; /**< Timer internal elapsed ticks queue. */
-static uint8_t m_ticks_elapsed_q_read_ind; /**< Timer internal elapsed ticks queue read index. */
-static uint8_t m_ticks_elapsed_q_write_ind; /**< Timer internal elapsed ticks queue write index. */
-static app_timer_evt_schedule_func_t m_evt_schedule_func; /**< Pointer to function for propagating timeout events to the scheduler. */
-static bool m_rtc1_running; /**< Boolean indicating if RTC1 is running. */
-static bool m_rtc1_reset; /**< Boolean indicating if RTC1 counter has been reset due to last timer removed from timer list during the timer list handling. */
-static volatile uint64_t overflowBits; /**< The upper 40 bits of the 64-bit value returned by cnt_get() */
-
-
-/**@brief Function for initializing the RTC1 counter.
- *
- * @param[in] prescaler Value of the RTC1 PRESCALER register. Set to 0 for no prescaling.
- */
-static void rtc1_init(uint32_t prescaler)
-{
- NRF_RTC1->PRESCALER = prescaler;
- NVIC_SetPriority(RTC1_IRQn, RTC1_IRQ_PRI);
-}
-
-
-/**@brief Function for starting the RTC1 timer.
- */
-static void rtc1_start(void)
-{
- if (m_rtc1_running) {
- return;
- }
-
- NRF_RTC1->EVTENSET = RTC_EVTEN_COMPARE0_Msk;
- NRF_RTC1->INTENSET = RTC_INTENSET_COMPARE0_Msk | RTC_INTENSET_OVRFLW_Msk;
-
- NVIC_ClearPendingIRQ(RTC1_IRQn);
- NVIC_EnableIRQ(RTC1_IRQn);
-
- NRF_RTC1->TASKS_START = 1;
- nrf_delay_us(MAX_RTC_TASKS_DELAY);
-
- m_rtc1_running = true;
-}
-
-
-/**@brief Function for stopping the RTC1 timer.
- */
-static void rtc1_stop(void)
-{
- if (!m_rtc1_running) {
- return;
- }
-
- NVIC_DisableIRQ(RTC1_IRQn);
-
- NRF_RTC1->EVTENCLR = RTC_EVTEN_COMPARE0_Msk;
- NRF_RTC1->INTENCLR = RTC_INTENSET_COMPARE0_Msk | RTC_INTENSET_OVRFLW_Msk;
-
- NRF_RTC1->TASKS_STOP = 1;
- nrf_delay_us(MAX_RTC_TASKS_DELAY);
-
- NRF_RTC1->TASKS_CLEAR = 1;
- m_ticks_latest = 0;
- nrf_delay_us(MAX_RTC_TASKS_DELAY);
-
- m_rtc1_running = false;
-}
-
-
-/**@brief Function for returning the current value of the RTC1 counter.
- *
- * @return Current value of the RTC1 counter.
- */
-static __INLINE uint32_t rtc1_counter_get(void)
-{
- return NRF_RTC1->COUNTER;
-}
-
-
-/**@brief Function for computing the difference between two RTC1 counter values.
- *
- * @return Number of ticks elapsed from ticks_old to ticks_now.
- */
-static __INLINE uint32_t ticks_diff_get(uint32_t ticks_now, uint32_t ticks_old)
-{
- return ((ticks_now - ticks_old) & MAX_RTC_COUNTER_VAL);
-}
-
-
-/**@brief Function for setting the RTC1 Capture Compare register 0, and enabling the corresponding
- * event.
- *
- * @param[in] value New value of Capture Compare register 0.
- */
-static __INLINE void rtc1_compare0_set(uint32_t value)
-{
- NRF_RTC1->CC[0] = value;
-}
-
-
-/**@brief Function for inserting a timer in the timer list.
- *
- * @param[in] timer_id Id of timer to insert.
- */
-static void timer_list_insert(app_timer_id_t timer_id)
-{
- timer_node_t * p_timer = &mp_nodes[timer_id];
-
- if (m_timer_id_head == TIMER_NULL)
- {
- m_timer_id_head = timer_id;
- }
- else
- {
- if (p_timer->ticks_to_expire <= mp_nodes[m_timer_id_head].ticks_to_expire)
- {
- mp_nodes[m_timer_id_head].ticks_to_expire -= p_timer->ticks_to_expire;
-
- p_timer->next = m_timer_id_head;
- m_timer_id_head = timer_id;
- }
- else
- {
- app_timer_id_t previous;
- app_timer_id_t current;
- uint32_t ticks_to_expire;
-
- ticks_to_expire = p_timer->ticks_to_expire;
- previous = m_timer_id_head;
- current = m_timer_id_head;
-
- while ((current != TIMER_NULL) && (ticks_to_expire > mp_nodes[current].ticks_to_expire))
- {
- ticks_to_expire -= mp_nodes[current].ticks_to_expire;
- previous = current;
- current = mp_nodes[current].next;
- }
-
- if (current != TIMER_NULL)
- {
- mp_nodes[current].ticks_to_expire -= ticks_to_expire;
- }
-
- p_timer->ticks_to_expire = ticks_to_expire;
- p_timer->next = current;
- mp_nodes[previous].next = timer_id;
- }
- }
-}
-
-
-/**@brief Function for removing a timer from the timer queue.
- *
- * @param[in] timer_id Id of timer to remove.
- */
-static void timer_list_remove(app_timer_id_t timer_id)
-{
- app_timer_id_t previous;
- app_timer_id_t current;
- uint32_t timeout;
-
- // Find the timer's position in timer list
- previous = m_timer_id_head;
- current = previous;
-
- while (current != TIMER_NULL)
- {
- if (current == timer_id)
- {
- break;
- }
- previous = current;
- current = mp_nodes[current].next;
- }
-
- // Timer not in active list
- if (current == TIMER_NULL)
- {
- return;
- }
-
- // Timer is the first in the list
- if (previous == current)
- {
- m_timer_id_head = mp_nodes[m_timer_id_head].next;
-
- // No more timers in the list. Reset RTC1 in case Start timer operations are present in the queue.
- if (m_timer_id_head == TIMER_NULL)
- {
- NRF_RTC1->TASKS_CLEAR = 1;
- m_ticks_latest = 0;
- m_rtc1_reset = true;
- }
- }
-
- // Remaining timeout between next timeout
- timeout = mp_nodes[current].ticks_to_expire;
-
- // Link previous timer with next of this timer, i.e. removing the timer from list
- mp_nodes[previous].next = mp_nodes[current].next;
-
- // If this is not the last timer, increment the next timer by this timer timeout
- current = mp_nodes[previous].next;
- if (current != TIMER_NULL)
- {
- mp_nodes[current].ticks_to_expire += timeout;
- }
-}
-
-
-/**@brief Function for scheduling a check for timeouts by generating a RTC1 interrupt.
- */
-static void timer_timeouts_check_sched(void)
-{
- NVIC_SetPendingIRQ(RTC1_IRQn);
-}
-
-
-/**@brief Function for scheduling a timer list update by generating a SWI0 interrupt.
- */
-static void timer_list_handler_sched(void)
-{
- NVIC_SetPendingIRQ(SWI0_IRQn);
-}
-
-
-/**@brief Function for executing an application timeout handler, either by calling it directly, or
- * by passing an event to the @ref app_scheduler.
- *
- * @param[in] p_timer Pointer to expired timer.
- */
-static void timeout_handler_exec(timer_node_t * p_timer)
-{
- if (m_evt_schedule_func != NULL)
- {
- uint32_t err_code = m_evt_schedule_func(p_timer->p_timeout_handler, p_timer->p_context);
- APP_ERROR_CHECK(err_code);
- }
- else
- {
- p_timer->p_timeout_handler(p_timer->p_context);
- }
-}
-
-
-/**@brief Function for checking for expired timers.
- */
-static void timer_timeouts_check(void)
-{
- // Handle expired of timer
- if (m_timer_id_head != TIMER_NULL)
- {
- app_timer_id_t timer_id;
- uint32_t ticks_elapsed;
- uint32_t ticks_expired;
-
- // Initialize actual elapsed ticks being consumed to 0
- ticks_expired = 0;
-
- // ticks_elapsed is collected here, job will use it
- ticks_elapsed = ticks_diff_get(rtc1_counter_get(), m_ticks_latest);
-
- // Auto variable containing the head of timers expiring
- timer_id = m_timer_id_head;
-
- // Expire all timers within ticks_elapsed and collect ticks_expired
- while (timer_id != TIMER_NULL)
- {
- timer_node_t * p_timer;
-
- // Auto variable for current timer node
- p_timer = &mp_nodes[timer_id];
-
- // Do nothing if timer did not expire
- if (ticks_elapsed < p_timer->ticks_to_expire)
- {
- break;
- }
-
- // Decrement ticks_elapsed and collect expired ticks
- ticks_elapsed -= p_timer->ticks_to_expire;
- ticks_expired += p_timer->ticks_to_expire;
-
- // Move to next timer
- timer_id = p_timer->next;
-
- // Execute Task
- timeout_handler_exec(p_timer);
- }
-
- // Prepare to queue the ticks expired in the m_ticks_elapsed queue.
- if (m_ticks_elapsed_q_read_ind == m_ticks_elapsed_q_write_ind)
- {
- // The read index of the queue is equal to the write index. This means the new
- // value of ticks_expired should be stored at a new location in the m_ticks_elapsed
- // queue (which is implemented as a double buffer).
-
- // Check if there will be a queue overflow.
- if (++m_ticks_elapsed_q_write_ind == CONTEXT_QUEUE_SIZE_MAX)
- {
- // There will be a queue overflow. Hence the write index should point to the start
- // of the queue.
- m_ticks_elapsed_q_write_ind = 0;
- }
- }
-
- // Queue the ticks expired.
- m_ticks_elapsed[m_ticks_elapsed_q_write_ind] = ticks_expired;
-
- timer_list_handler_sched();
- }
-}
-
-
-/**@brief Function for acquiring the number of ticks elapsed.
- *
- * @param[out] p_ticks_elapsed Number of ticks elapsed.
- *
- * @return TRUE if elapsed ticks was read from queue, FALSE otherwise.
- */
-static bool elapsed_ticks_acquire(uint32_t * p_ticks_elapsed)
-{
- // Pick the elapsed value from queue
- if (m_ticks_elapsed_q_read_ind != m_ticks_elapsed_q_write_ind)
- {
- // Dequeue elapsed value
- m_ticks_elapsed_q_read_ind++;
- if (m_ticks_elapsed_q_read_ind == CONTEXT_QUEUE_SIZE_MAX)
- {
- m_ticks_elapsed_q_read_ind = 0;
- }
-
- *p_ticks_elapsed = m_ticks_elapsed[m_ticks_elapsed_q_read_ind];
-
- m_ticks_latest += *p_ticks_elapsed;
- m_ticks_latest &= MAX_RTC_COUNTER_VAL;
-
- return true;
- }
- else
- {
- // No elapsed value in queue
- *p_ticks_elapsed = 0;
- return false;
- }
-}
-
-
-/**@brief Function for handling the timer list deletions.
- *
- * @return TRUE if Capture Compare register must be updated, FALSE otherwise.
- */
-static bool list_deletions_handler(void)
-{
- app_timer_id_t timer_id_old_head;
- uint8_t user_id;
-
- // Remember the old head, so as to decide if new compare needs to be set
- timer_id_old_head = m_timer_id_head;
-
- user_id = m_user_array_size;
- while (user_id--)
- {
- timer_user_t * p_user = &mp_users[user_id];
- uint8_t user_ops_first = p_user->first;
-
- while (user_ops_first != p_user->last)
- {
- timer_node_t * p_timer;
- timer_user_op_t * p_user_op = &p_user->p_user_op_queue[user_ops_first];
-
- // Traverse to next operation in queue
- user_ops_first++;
- if (user_ops_first == p_user->user_op_queue_size)
- {
- user_ops_first = 0;
- }
-
- switch (p_user_op->op_type)
- {
- case TIMER_USER_OP_TYPE_STOP:
- // Delete node if timer is running
- p_timer = &mp_nodes[p_user_op->timer_id];
- if (p_timer->is_running)
- {
- timer_list_remove(p_user_op->timer_id);
- p_timer->is_running = false;
- }
- break;
-
- case TIMER_USER_OP_TYPE_STOP_ALL:
- // Delete list of running timers, and mark all timers as not running
- while (m_timer_id_head != TIMER_NULL)
- {
- timer_node_t * p_head = &mp_nodes[m_timer_id_head];
-
- p_head->is_running = false;
- m_timer_id_head = p_head->next;
- }
- break;
-
- default:
- // No implementation needed.
- break;
- }
- }
- }
-
- // Detect change in head of the list
- return (m_timer_id_head != timer_id_old_head);
-}
-
-
-/**@brief Function for updating the timer list for expired timers.
- *
- * @param[in] ticks_elapsed Number of elapsed ticks.
- * @param[in] ticks_previous Previous known value of the RTC counter.
- * @param[out] p_restart_list_head List of repeating timers to be restarted.
- */
-static void expired_timers_handler(uint32_t ticks_elapsed,
- uint32_t ticks_previous,
- app_timer_id_t * p_restart_list_head)
-{
- uint32_t ticks_expired = 0;
-
- while (m_timer_id_head != TIMER_NULL)
- {
- timer_node_t * p_timer;
- app_timer_id_t id_expired;
-
- // Auto variable for current timer node
- p_timer = &mp_nodes[m_timer_id_head];
-
- // Do nothing if timer did not expire
- if (ticks_elapsed < p_timer->ticks_to_expire)
- {
- p_timer->ticks_to_expire -= ticks_elapsed;
- break;
- }
-
- // Decrement ticks_elapsed and collect expired ticks
- ticks_elapsed -= p_timer->ticks_to_expire;
- ticks_expired += p_timer->ticks_to_expire;
-
- // Timer expired, set ticks_to_expire zero
- p_timer->ticks_to_expire = 0;
- p_timer->is_running = false;
-
- // Remove the expired timer from head
- id_expired = m_timer_id_head;
- m_timer_id_head = p_timer->next;
-
- // Timer will be restarted if periodic
- if (p_timer->ticks_periodic_interval != 0)
- {
- p_timer->ticks_at_start = (ticks_previous + ticks_expired) & MAX_RTC_COUNTER_VAL;
- p_timer->ticks_first_interval = p_timer->ticks_periodic_interval;
- p_timer->next = *p_restart_list_head;
- *p_restart_list_head = id_expired;
- }
- }
-}
-
-
-/**@brief Function for handling timer list insertions.
- *
- * @param[in] p_restart_list_head List of repeating timers to be restarted.
- *
- * @return TRUE if Capture Compare register must be updated, FALSE otherwise.
- */
-static bool list_insertions_handler(app_timer_id_t restart_list_head)
-{
- app_timer_id_t timer_id_old_head;
- uint8_t user_id;
-
- // Remember the old head, so as to decide if new compare needs to be set
- timer_id_old_head = m_timer_id_head;
-
- user_id = m_user_array_size;
- while (user_id--)
- {
- timer_user_t * p_user = &mp_users[user_id];
-
- // Handle insertions of timers
- while ((restart_list_head != TIMER_NULL) || (p_user->first != p_user->last))
- {
- app_timer_id_t id_start;
- timer_node_t * p_timer;
-
- if (restart_list_head != TIMER_NULL)
- {
- id_start = restart_list_head;
- p_timer = &mp_nodes[id_start];
- restart_list_head = p_timer->next;
- }
- else
- {
- timer_user_op_t * p_user_op = &p_user->p_user_op_queue[p_user->first];
-
- p_user->first++;
- if (p_user->first == p_user->user_op_queue_size)
- {
- p_user->first = 0;
- }
-
- id_start = p_user_op->timer_id;
- p_timer = &mp_nodes[id_start];
-
- if ((p_user_op->op_type != TIMER_USER_OP_TYPE_START) || p_timer->is_running)
- {
- continue;
- }
-
- p_timer->ticks_at_start = p_user_op->params.start.ticks_at_start;
- p_timer->ticks_first_interval = p_user_op->params.start.ticks_first_interval;
- p_timer->ticks_periodic_interval = p_user_op->params.start.ticks_periodic_interval;
- p_timer->p_context = p_user_op->params.start.p_context;
-
- if (m_rtc1_reset)
- {
- p_timer->ticks_at_start = 0;
- }
- }
-
- // Prepare the node to be inserted.
- if (
- ((p_timer->ticks_at_start - m_ticks_latest) & MAX_RTC_COUNTER_VAL)
- <
- (MAX_RTC_COUNTER_VAL / 2)
- )
- {
- p_timer->ticks_to_expire = ticks_diff_get(p_timer->ticks_at_start, m_ticks_latest) +
- p_timer->ticks_first_interval;
- }
- else
- {
- uint32_t delta_current_start;
-
- delta_current_start = ticks_diff_get(m_ticks_latest, p_timer->ticks_at_start);
- if (p_timer->ticks_first_interval > delta_current_start)
- {
- p_timer->ticks_to_expire = p_timer->ticks_first_interval - delta_current_start;
- }
- else
- {
- p_timer->ticks_to_expire = 0;
- }
- }
-
- p_timer->ticks_at_start = 0;
- p_timer->ticks_first_interval = 0;
- p_timer->is_running = true;
- p_timer->next = TIMER_NULL;
-
- // Insert into list
- timer_list_insert(id_start);
- }
- }
-
- return (m_timer_id_head != timer_id_old_head);
-}
-
-
-/**@brief Function for updating the Capture Compare register.
- */
-static void compare_reg_update(app_timer_id_t timer_id_head_old)
-{
- // Setup the timeout for timers on the head of the list
- if (m_timer_id_head != TIMER_NULL)
- {
- uint32_t ticks_to_expire = mp_nodes[m_timer_id_head].ticks_to_expire;
- uint32_t pre_counter_val = rtc1_counter_get();
- uint32_t cc = m_ticks_latest;
- uint32_t ticks_elapsed = ticks_diff_get(pre_counter_val, cc) + RTC_COMPARE_OFFSET_MIN;
-
- if (!m_rtc1_running)
- {
- // No timers were already running, start RTC
- rtc1_start();
- }
-
- cc += (ticks_elapsed < ticks_to_expire) ? ticks_to_expire : ticks_elapsed;
- cc &= MAX_RTC_COUNTER_VAL;
-
- rtc1_compare0_set(cc);
-
- uint32_t post_counter_val = rtc1_counter_get();
-
- if ((ticks_diff_get(post_counter_val, pre_counter_val) + RTC_COMPARE_OFFSET_MIN) > ticks_diff_get(cc, pre_counter_val))
- {
- // When this happens the COMPARE event may not be triggered by the RTC.
- // The nRF51 Series User Specification states that if the COUNTER value is N
- // (i.e post_counter_val = N), writing N or N+1 to a CC register may not trigger a
- // COMPARE event. Hence the RTC interrupt is forcefully pended by calling the following
- // function.
- timer_timeouts_check_sched();
- }
- }
- else
- {
- // No timers are running, stop RTC
- rtc1_stop();
- }
-}
-
-
-/**@brief Function for handling changes to the timer list.
- */
-static void timer_list_handler(void)
-{
- app_timer_id_t restart_list_head = TIMER_NULL;
- uint32_t ticks_elapsed;
- uint32_t ticks_previous;
- bool ticks_have_elapsed;
- bool compare_update;
- app_timer_id_t timer_id_head_old;
-
- // Back up the previous known tick and previous list head
- ticks_previous = m_ticks_latest;
- timer_id_head_old = m_timer_id_head;
-
- // Get number of elapsed ticks
- ticks_have_elapsed = elapsed_ticks_acquire(&ticks_elapsed);
-
- // Handle list deletions
- compare_update = list_deletions_handler();
-
- // Handle expired timers
- if (ticks_have_elapsed)
- {
- expired_timers_handler(ticks_elapsed, ticks_previous, &restart_list_head);
- compare_update = true;
- }
-
- // Handle list insertions
- if (list_insertions_handler(restart_list_head))
- {
- compare_update = true;
- }
-
- // Update compare register if necessary
- if (compare_update)
- {
- compare_reg_update(timer_id_head_old);
- }
- m_rtc1_reset = false;
-}
-
-
-/**@brief Function for enqueueing a new operations queue entry.
- *
- * @param[in] p_user User that the entry is to be enqueued for.
- * @param[in] last_index Index of the next last index to be enqueued.
- */
-static void user_op_enque(timer_user_t * p_user, app_timer_id_t last_index)
-{
- p_user->last = last_index;
-}
-
-
-/**@brief Function for allocating a new operations queue entry.
- *
- * @param[in] p_user User that the entry is to be allocated for.
- * @param[out] p_last_index Index of the next last index to be enqueued.
- *
- * @return Pointer to allocated queue entry, or NULL if queue is full.
- */
-static timer_user_op_t * user_op_alloc(timer_user_t * p_user, app_timer_id_t * p_last_index)
-{
- app_timer_id_t last;
- timer_user_op_t * p_user_op;
-
- last = p_user->last + 1;
- if (last == p_user->user_op_queue_size)
- {
- // Overflow case.
- last = 0;
- }
- if (last == p_user->first)
- {
- // Queue is full.
- return NULL;
- }
-
- *p_last_index = last;
- p_user_op = &p_user->p_user_op_queue[p_user->last];
-
- return p_user_op;
-}
-
-
-/**@brief Function for scheduling a Timer Start operation.
- *
- * @param[in] user_id Id of user calling this function.
- * @param[in] timer_id Id of timer to start.
- * @param[in] timeout_initial Time (in ticks) to first timer expiry.
- * @param[in] timeout_periodic Time (in ticks) between periodic expiries.
- * @param[in] p_context General purpose pointer. Will be passed to the timeout handler when
- * the timer expires.
- * @return NRF_SUCCESS on success, otherwise an error code.
- */
-static uint32_t timer_start_op_schedule(timer_user_id_t user_id,
- app_timer_id_t timer_id,
- uint32_t timeout_initial,
- uint32_t timeout_periodic,
- void * p_context)
-{
- app_timer_id_t last_index;
-
- timer_user_op_t * p_user_op = user_op_alloc(&mp_users[user_id], &last_index);
- if (p_user_op == NULL)
- {
- return NRF_ERROR_NO_MEM;
- }
-
- p_user_op->op_type = TIMER_USER_OP_TYPE_START;
- p_user_op->timer_id = timer_id;
- p_user_op->params.start.ticks_at_start = rtc1_counter_get();
- p_user_op->params.start.ticks_first_interval = timeout_initial;
- p_user_op->params.start.ticks_periodic_interval = timeout_periodic;
- p_user_op->params.start.p_context = p_context;
-
- user_op_enque(&mp_users[user_id], last_index);
-
- timer_list_handler_sched();
-
- return NRF_SUCCESS;
-}
-
-
-/**@brief Function for scheduling a Timer Stop operation.
- *
- * @param[in] user_id Id of user calling this function.
- * @param[in] timer_id Id of timer to stop.
- *
- * @return NRF_SUCCESS on successful scheduling a timer stop operation. NRF_ERROR_NO_MEM when there
- * is no memory left to schedule the timer stop operation.
- */
-static uint32_t timer_stop_op_schedule(timer_user_id_t user_id, app_timer_id_t timer_id)
-{
- app_timer_id_t last_index;
-
- timer_user_op_t * p_user_op = user_op_alloc(&mp_users[user_id], &last_index);
- if (p_user_op == NULL)
- {
- return NRF_ERROR_NO_MEM;
- }
-
- p_user_op->op_type = TIMER_USER_OP_TYPE_STOP;
- p_user_op->timer_id = timer_id;
-
- user_op_enque(&mp_users[user_id], last_index);
-
- timer_list_handler_sched();
-
- return NRF_SUCCESS;
-}
-
-
-/**@brief Function for scheduling a Timer Stop All operation.
- *
- * @param[in] user_id Id of user calling this function.
- */
-static uint32_t timer_stop_all_op_schedule(timer_user_id_t user_id)
-{
- app_timer_id_t last_index;
-
- timer_user_op_t * p_user_op = user_op_alloc(&mp_users[user_id], &last_index);
- if (p_user_op == NULL)
- {
- return NRF_ERROR_NO_MEM;
- }
-
- p_user_op->op_type = TIMER_USER_OP_TYPE_STOP_ALL;
- p_user_op->timer_id = TIMER_NULL;
-
- user_op_enque(&mp_users[user_id], last_index);
-
- timer_list_handler_sched();
-
- return NRF_SUCCESS;
-}
-
-
-/**@brief Function for handling the RTC1 interrupt.
- *
- * @details Checks for timeouts, and executes timeout handlers for expired timers.
- */
-void RTC1_IRQHandler(void)
-{
- // Clear all events (also unexpected ones)
- NRF_RTC1->EVENTS_COMPARE[0] = 0;
- NRF_RTC1->EVENTS_COMPARE[1] = 0;
- NRF_RTC1->EVENTS_COMPARE[2] = 0;
- NRF_RTC1->EVENTS_COMPARE[3] = 0;
- NRF_RTC1->EVENTS_TICK = 0;
- if (NRF_RTC1->EVENTS_OVRFLW) {
- overflowBits += (1 << 24);
- }
- NRF_RTC1->EVENTS_OVRFLW = 0;
-
- // Check for expired timers
- timer_timeouts_check();
-}
-
-/**@brief Function for handling the SWI0 interrupt.
- *
- * @details Performs all updates to the timer list.
- */
-void SWI0_IRQHandler(void)
-{
- timer_list_handler();
-}
-
-uint32_t app_timer_init(uint32_t prescaler,
- uint8_t max_timers,
- uint8_t op_queues_size,
- void * p_buffer,
- app_timer_evt_schedule_func_t evt_schedule_func)
-{
- int i;
-
- // Check that buffer is correctly aligned
- if (!is_word_aligned(p_buffer))
- {
- return NRF_ERROR_INVALID_PARAM;
- }
- // Check for NULL buffer
- if (p_buffer == NULL)
- {
- return NRF_ERROR_INVALID_PARAM;
- }
-
- // Stop RTC to prevent any running timers from expiring (in case of reinitialization)
- rtc1_stop();
-
- m_evt_schedule_func = evt_schedule_func;
-
- // Initialize timer node array
- m_node_array_size = max_timers;
- mp_nodes = (timer_node_t *) p_buffer;
-
- for (i = 0; i < max_timers; i++)
- {
- mp_nodes[i].state = STATE_FREE;
- mp_nodes[i].is_running = false;
- }
-
- // Skip timer node array
- p_buffer = &((uint8_t *)p_buffer)[max_timers * sizeof(timer_node_t)];
-
- // Initialize users array
- m_user_array_size = APP_TIMER_INT_LEVELS;
- mp_users = (timer_user_t *) p_buffer;
-
- // Skip user array
- p_buffer = &((uint8_t *)p_buffer)[APP_TIMER_INT_LEVELS * sizeof(timer_user_t)];
-
- // Initialize operation queues
- for (i = 0; i < APP_TIMER_INT_LEVELS; i++)
- {
- timer_user_t * p_user = &mp_users[i];
-
- p_user->first = 0;
- p_user->last = 0;
- p_user->user_op_queue_size = op_queues_size;
- p_user->p_user_op_queue = (timer_user_op_t *) p_buffer;
-
- // Skip operation queue
- p_buffer = &((uint8_t *)p_buffer)[op_queues_size * sizeof(timer_user_op_t)];
- }
-
- m_timer_id_head = TIMER_NULL;
- m_ticks_elapsed_q_read_ind = 0;
- m_ticks_elapsed_q_write_ind = 0;
-
- NVIC_ClearPendingIRQ(SWI0_IRQn);
- NVIC_SetPriority(SWI0_IRQn, SWI0_IRQ_PRI);
- NVIC_EnableIRQ(SWI0_IRQn);
-
- rtc1_init(prescaler);
- rtc1_start();
-
- m_ticks_latest = rtc1_counter_get();
-
- return NRF_SUCCESS;
-}
-
-
-uint32_t app_timer_create(app_timer_id_t * p_timer_id,
- app_timer_mode_t mode,
- app_timer_timeout_handler_t timeout_handler)
-{
- int i;
-
- // Check state and parameters
- if (mp_nodes == NULL)
- {
- return NRF_ERROR_INVALID_STATE;
- }
- if (timeout_handler == NULL)
- {
- return NRF_ERROR_INVALID_PARAM;
- }
- if (p_timer_id == NULL)
- {
- return NRF_ERROR_INVALID_PARAM;
- }
-
- // Find free timer
- for (i = 0; i < m_node_array_size; i++)
- {
- if (mp_nodes[i].state == STATE_FREE)
- {
- mp_nodes[i].state = STATE_ALLOCATED;
- mp_nodes[i].mode = mode;
- mp_nodes[i].p_timeout_handler = timeout_handler;
-
- *p_timer_id = i;
- return NRF_SUCCESS;
- }
- }
-
- return NRF_ERROR_NO_MEM;
-}
-
-
-/**@brief Function for creating a timer user id from the current interrupt level.
- *
- * @return Timer user id.
-*/
-static timer_user_id_t user_id_get(void)
-{
- timer_user_id_t ret;
-
- STATIC_ASSERT(APP_TIMER_INT_LEVELS == 3);
-
- switch (current_int_priority_get())
- {
- case APP_IRQ_PRIORITY_HIGH:
- ret = APP_HIGH_USER_ID;
- break;
-
- case APP_IRQ_PRIORITY_LOW:
- ret = APP_LOW_USER_ID;
- break;
-
- default:
- ret = THREAD_MODE_USER_ID;
- break;
- }
-
- return ret;
-}
-
-
-uint32_t app_timer_start(app_timer_id_t timer_id, uint32_t timeout_ticks, void * p_context)
-{
- uint32_t timeout_periodic;
-
- // Check state and parameters
- if (mp_nodes == NULL)
- {
- return NRF_ERROR_INVALID_STATE;
- }
- if ((timer_id >= m_node_array_size) || (timeout_ticks < APP_TIMER_MIN_TIMEOUT_TICKS))
- {
- return NRF_ERROR_INVALID_PARAM;
- }
- if (mp_nodes[timer_id].state != STATE_ALLOCATED)
- {
- return NRF_ERROR_INVALID_STATE;
- }
-
- // Schedule timer start operation
- timeout_periodic = (mp_nodes[timer_id].mode == APP_TIMER_MODE_REPEATED) ? timeout_ticks : 0;
-
- return timer_start_op_schedule(user_id_get(),
- timer_id,
- timeout_ticks,
- timeout_periodic,
- p_context);
-}
-
-
-uint32_t app_timer_stop(app_timer_id_t timer_id)
-{
- // Check state and parameters
- if (mp_nodes == NULL)
- {
- return NRF_ERROR_INVALID_STATE;
- }
- if (timer_id >= m_node_array_size)
- {
- return NRF_ERROR_INVALID_PARAM;
- }
- if (mp_nodes[timer_id].state != STATE_ALLOCATED)
- {
- return NRF_ERROR_INVALID_STATE;
- }
-
- // Schedule timer stop operation
- return timer_stop_op_schedule(user_id_get(), timer_id);
-}
-
-
-uint32_t app_timer_stop_all(void)
-{
- // Check state
- if (mp_nodes == NULL)
- {
- return NRF_ERROR_INVALID_STATE;
- }
-
- return timer_stop_all_op_schedule(user_id_get());
-}
-
-
-uint32_t app_timer_cnt_get(uint64_t * p_ticks)
-{
- *p_ticks = overflowBits | rtc1_counter_get();
- return NRF_SUCCESS;
-}
-
-
-uint32_t app_timer_cnt_diff_compute(uint32_t ticks_to,
- uint32_t ticks_from,
- uint32_t * p_ticks_diff)
-{
- *p_ticks_diff = ticks_diff_get(ticks_to, ticks_from);
- return NRF_SUCCESS;
-}
--- a/targets/hal/TARGET_NORDIC/TARGET_MCU_NRF51822/us_ticker.c Fri Mar 20 09:15:08 2015 +0000
+++ b/targets/hal/TARGET_NORDIC/TARGET_MCU_NRF51822/us_ticker.c Fri Mar 20 09:30:08 2015 +0000
@@ -14,14 +14,157 @@
* limitations under the License.
*/
#include <stddef.h>
+#include <stdbool.h>
#include "us_ticker_api.h"
#include "cmsis.h"
#include "PeripheralNames.h"
-#include "app_timer.h"
+#include "nrf_delay.h"
+
+/*
+ * Note: The micro-second timer API on the nRF51 platform is implemented using
+ * the RTC counter run at 32kHz (sourced from an external oscillator). This is
+ * a trade-off between precision and power. Running a normal 32-bit MCU counter
+ * at high frequency causes the average power consumption to rise to a few
+ * hundred micro-amps, which is prohibitive for typical low-power BLE
+ * applications.
+ * A 32kHz clock doesn't offer the precision needed for keeping u-second time,
+ * but we're assuming that this will not be a problem for the average user.
+ */
+
+#define MAX_RTC_COUNTER_VAL 0x00FFFFFF /**< Maximum value of the RTC counter. */
+#define RTC_CLOCK_FREQ (uint32_t)(32768)
+#define RTC1_IRQ_PRI 3 /**< Priority of the RTC1 interrupt (used
+ * for checking for timeouts and executing
+ * timeout handlers). This must be the same
+ * as APP_IRQ_PRIORITY_LOW; taken from the
+ * Nordic SDK. */
+#define MAX_RTC_TASKS_DELAY 47 /**< Maximum delay until an RTC task is executed. */
+
+#define FUZZY_RTC_TICKS 2 /* RTC COMPARE occurs when a CC register is N and the RTC
+ * COUNTER value transitions from N-1 to N. If we're trying to
+ * setup a callback for a time which will arrive very shortly,
+ * there are limits to how short the callback interval may be for us
+ * to rely upon the RTC Compare trigger. If the COUNTER is N,
+ * writing N+2 to a CC register is guaranteed to trigger a COMPARE
+ * event at N+2. */
+
+#define RTC_UNITS_TO_MICROSECONDS(RTC_UNITS) (((RTC_UNITS) * (uint64_t)1000000) / RTC_CLOCK_FREQ)
+#define MICROSECONDS_TO_RTC_UNITS(MICROS) ((((uint64_t)(MICROS) * RTC_CLOCK_FREQ) + 999999) / 1000000)
+
+static bool us_ticker_inited = false;
+static volatile uint32_t overflowCount; /**< The number of times the 24-bit RTC counter has overflowed. */
+static volatile bool us_ticker_callbackPending = false;
+static uint32_t us_ticker_callbackTimestamp;
+
+static inline void rtc1_enableCompareInterrupt(void)
+{
+ NRF_RTC1->EVTENCLR = RTC_EVTEN_COMPARE0_Msk;
+ NRF_RTC1->INTENSET = RTC_INTENSET_COMPARE0_Msk;
+}
+
+static inline void rtc1_disableCompareInterrupt(void)
+{
+ NRF_RTC1->INTENCLR = RTC_INTENSET_COMPARE0_Msk;
+ NRF_RTC1->EVTENCLR = RTC_EVTEN_COMPARE0_Msk;
+}
+
+static inline void rtc1_enableOverflowInterrupt(void)
+{
+ NRF_RTC1->EVTENCLR = RTC_EVTEN_OVRFLW_Msk;
+ NRF_RTC1->INTENSET = RTC_INTENSET_OVRFLW_Msk;
+}
+
+static inline void rtc1_disableOverflowInterrupt(void)
+{
+ NRF_RTC1->INTENCLR = RTC_INTENSET_OVRFLW_Msk;
+ NRF_RTC1->EVTENCLR = RTC_EVTEN_OVRFLW_Msk;
+}
+
+static inline void invokeCallback(void)
+{
+ us_ticker_callbackPending = false;
+ rtc1_disableCompareInterrupt();
+ us_ticker_irq_handler();
+}
-static bool us_ticker_inited = false;
-static volatile bool us_ticker_appTimerRunning = false;
-static app_timer_id_t us_ticker_appTimerID = TIMER_NULL;
+/**
+ * @brief Function for starting the RTC1 timer. The RTC timer is expected to
+ * keep running--some interrupts may be disabled temporarily.
+ */
+static void rtc1_start()
+{
+ NRF_RTC1->PRESCALER = 0; /* for no pre-scaling. */
+
+ rtc1_enableOverflowInterrupt();
+
+ NVIC_SetPriority(RTC1_IRQn, RTC1_IRQ_PRI);
+ NVIC_ClearPendingIRQ(RTC1_IRQn);
+ NVIC_EnableIRQ(RTC1_IRQn);
+
+ NRF_RTC1->TASKS_START = 1;
+ nrf_delay_us(MAX_RTC_TASKS_DELAY);
+}
+
+/**
+ * @brief Function for stopping the RTC1 timer. We don't expect to call this.
+ */
+void rtc1_stop(void)
+{
+ NVIC_DisableIRQ(RTC1_IRQn);
+ rtc1_disableCompareInterrupt();
+ rtc1_disableOverflowInterrupt();
+
+ NRF_RTC1->TASKS_STOP = 1;
+ nrf_delay_us(MAX_RTC_TASKS_DELAY);
+
+ NRF_RTC1->TASKS_CLEAR = 1;
+ nrf_delay_us(MAX_RTC_TASKS_DELAY);
+}
+
+/**
+ * @brief Function for returning the current value of the RTC1 counter.
+ *
+ * @return Current RTC1 counter as a 64-bit value with 56-bit precision (even
+ * though the underlying counter is 24-bit)
+ */
+static inline uint64_t rtc1_getCounter64(void)
+{
+ if (NRF_RTC1->EVENTS_OVRFLW) {
+ overflowCount++;
+ NRF_RTC1->EVENTS_OVRFLW = 0;
+ NRF_RTC1->EVTENCLR = RTC_EVTEN_OVRFLW_Msk;
+ }
+ return ((uint64_t)overflowCount << 24) | NRF_RTC1->COUNTER;
+}
+
+/**
+ * @brief Function for returning the current value of the RTC1 counter.
+ *
+ * @return Current RTC1 counter as a 32-bit value (even though the underlying counter is 24-bit)
+ */
+static inline uint32_t rtc1_getCounter(void)
+{
+ return rtc1_getCounter64();
+}
+
+/**
+ * @brief Function for handling the RTC1 interrupt.
+ *
+ * @details Checks for timeouts, and executes timeout handlers for expired timers.
+ */
+void RTC1_IRQHandler(void)
+{
+ if (NRF_RTC1->EVENTS_OVRFLW) {
+ overflowCount++;
+ NRF_RTC1->EVENTS_OVRFLW = 0;
+ NRF_RTC1->EVTENCLR = RTC_EVTEN_OVRFLW_Msk;
+ }
+ if (NRF_RTC1->EVENTS_COMPARE[0] && us_ticker_callbackPending && ((int)(us_ticker_callbackTimestamp - rtc1_getCounter()) <= 0)) {
+ NRF_RTC1->EVENTS_COMPARE[0] = 0;
+ NRF_RTC1->EVTENCLR = RTC_EVTEN_COMPARE0_Msk;
+ invokeCallback();
+ }
+}
void us_ticker_init(void)
{
@@ -29,7 +172,7 @@
return;
}
-APP_TIMER_INIT(0 /*CFG_TIMER_PRESCALER*/ , 1 /*CFG_TIMER_MAX_INSTANCE*/, 1 /*CFG_TIMER_OPERATION_QUEUE_SIZE*/, false /*CFG_SCHEDULER_ENABLE*/);
+ rtc1_start();
us_ticker_inited = true;
}
@@ -39,71 +182,91 @@
us_ticker_init();
}
- uint64_t value;
- app_timer_cnt_get(&value); /* This returns the RTC counter (which is fed by the 32khz crystal clock source) */
- return ((value * 1000000) / (uint32_t)APP_TIMER_CLOCK_FREQ); /* Return a pseudo microsecond counter value.
- * This is only as precise as the 32khz low-freq
- * clock source, but could be adequate.*/
+ /* Return a pseudo microsecond counter value. This is only as precise as the
+ * 32khz low-freq clock source, but could be adequate.*/
+ return RTC_UNITS_TO_MICROSECONDS(rtc1_getCounter64());
}
-/* An adaptor to interface us_ticker_irq_handler with the app_timer callback.
- * Needed because the irq_handler() doesn't take any parameter.*/
-static void us_ticker_app_timer_callback(void *context)
-{
- us_ticker_appTimerRunning = false;
- us_ticker_irq_handler();
-}
-
+/**
+ * Setup the us_ticker callback interrupt to go at the given timestamp.
+ *
+ * @Note: Only one callback is pending at any time.
+ *
+ * @Note: If a callback is pending, and this function is called again, the new
+ * callback-time overrides the existing callback setting. It is the caller's
+ * responsibility to ensure that this function is called to setup a callback for
+ * the earliest timeout.
+ *
+ * @Note: If this function is used to setup an interrupt which is immediately
+ * pending--such as for 'now' or a time in the past,--then the callback is
+ * invoked a few ticks later.
+ */
void us_ticker_set_interrupt(timestamp_t timestamp)
{
if (!us_ticker_inited) {
us_ticker_init();
}
- if (us_ticker_appTimerID == TIMER_NULL) {
- if (app_timer_create(&us_ticker_appTimerID, APP_TIMER_MODE_SINGLE_SHOT, us_ticker_app_timer_callback) != NRF_SUCCESS) {
- /* placeholder to do something to recover from error */
- return;
- }
+ /*
+ * The argument to this function is a 32-bit microsecond timestamp for when
+ * a callback should be invoked. On the nRF51, we use an RTC timer running
+ * at 32kHz to implement a low-power us-ticker. This results in a problem
+ * based on the fact that 1000000 is not a multiple of 32768.
+ *
+ * Going from a micro-second based timestamp to a 32kHz based RTC-time is a
+ * linear mapping; but this mapping doesn't preserve wraparounds--i.e. when
+ * the 32-bit micro-second timestamp wraps around unfortunately the
+ * underlying RTC counter doesn't. The result is that timestamp expiry
+ * checks on micro-second timestamps don't yield the same result when
+ * applied on the corresponding RTC timestamp values.
+ *
+ * One solution is to translate the incoming 32-bit timestamp into a virtual
+ * 64-bit timestamp based on the knowledge of system-uptime, and then use
+ * this wraparound-free 64-bit value to do a linear mapping to RTC time.
+ * System uptime on an nRF is maintained using the 24-bit RTC counter. We
+ * track the overflow count to extend the 24-bit hardware counter by an
+ * additional 32 bits. RTC_UNITS_TO_MICROSECONDS() converts this into
+ * microsecond units (in 64-bits).
+ */
+ const uint64_t currentTime64 = RTC_UNITS_TO_MICROSECONDS(rtc1_getCounter64());
+ uint64_t timestamp64 = (currentTime64 & ~(uint64_t)0xFFFFFFFFULL) + timestamp;
+ if (((uint32_t)currentTime64 > 0x80000000) && (timestamp < 0x80000000)) {
+ timestamp64 += (uint64_t)0x100000000ULL;
}
+ uint32_t newCallbackTime = MICROSECONDS_TO_RTC_UNITS(timestamp64);
- if (us_ticker_appTimerRunning) {
+ /* Check for repeat setup of an existing callback. This is actually not
+ * important; the following code should work even without this check. */
+ if (us_ticker_callbackPending && (newCallbackTime == us_ticker_callbackTimestamp)) {
return;
}
- uint64_t currentCounter64;
- app_timer_cnt_get(¤tCounter64);
- uint32_t currentCounter = currentCounter64 & MAX_RTC_COUNTER_VAL;
- uint32_t targetCounter = ((uint32_t)((timestamp * (uint64_t)APP_TIMER_CLOCK_FREQ) / 1000000) + 1) & MAX_RTC_COUNTER_VAL;
- uint32_t ticksToCount = (targetCounter >= currentCounter) ?
- (targetCounter - currentCounter) : (MAX_RTC_COUNTER_VAL + 1) - (currentCounter - targetCounter);
- if (ticksToCount < APP_TIMER_MIN_TIMEOUT_TICKS) { /* Honour the minimum value of the timeout_ticks parameter of app_timer_start() */
- ticksToCount = APP_TIMER_MIN_TIMEOUT_TICKS;
+ /* Check for callbacks which are immediately (or will *very* shortly become) pending.
+ * Even if they are immediately pending, they are scheduled to trigger a few
+ * ticks later. This keeps things simple by invoking the callback from an
+ * independent interrupt context. */
+ if ((int)(newCallbackTime - rtc1_getCounter()) <= (int)FUZZY_RTC_TICKS) {
+ newCallbackTime = rtc1_getCounter() + FUZZY_RTC_TICKS;
}
- uint32_t rc;
- rc = app_timer_start(us_ticker_appTimerID, ticksToCount, NULL /*p_context*/);
- if (rc != NRF_SUCCESS) {
- /* placeholder to do something to recover from error */
- return;
+ NRF_RTC1->CC[0] = newCallbackTime & MAX_RTC_COUNTER_VAL;
+ us_ticker_callbackTimestamp = newCallbackTime;
+ if (!us_ticker_callbackPending) {
+ us_ticker_callbackPending = true;
+ rtc1_enableCompareInterrupt();
}
- us_ticker_appTimerRunning = true;
}
void us_ticker_disable_interrupt(void)
{
- if (us_ticker_appTimerRunning) {
- if (app_timer_stop(us_ticker_appTimerID) == NRF_SUCCESS) {
- us_ticker_appTimerRunning = false;
- }
+ if (us_ticker_callbackPending) {
+ rtc1_disableCompareInterrupt();
+ us_ticker_callbackPending = false;
}
}
void us_ticker_clear_interrupt(void)
{
- if (us_ticker_appTimerRunning) {
- if (app_timer_stop(us_ticker_appTimerID) == NRF_SUCCESS) {
- us_ticker_appTimerRunning = false;
- }
- }
+ NRF_RTC1->EVENTS_OVRFLW = 0;
+ NRF_RTC1->EVENTS_COMPARE[0] = 0;
}