PicoSDK
Select one of the symbols to view example projects that use it.
 
Outline
#define _PICO_SEM_H
#include "pico/lock_core.h"
semaphore
sem_init(semaphore_t *, int16_t, int16_t);
sem_available(semaphore_t *);
sem_release(semaphore_t *);
sem_reset(semaphore_t *, int16_t);
sem_acquire_blocking(semaphore_t *);
sem_acquire_timeout_ms(semaphore_t *, uint32_t);
sem_acquire_timeout_us(semaphore_t *, uint32_t);
sem_acquire_block_until(semaphore_t *, absolute_time_t);
sem_try_acquire(semaphore_t *);
Files
loading...
SourceVuRaspberry Pi Pico SDK and ExamplesPicoSDKsrc/common/pico_sync/include/pico/sem.h
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
/* * Copyright (c) 2020 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause *//* ... */ #ifndef _PICO_SEM_H #define _PICO_SEM_H #include "pico/lock_core.h" /** \file sem.h * \defgroup sem sem * \ingroup pico_sync * \brief Semaphore API for restricting access to a resource * * A semaphore holds a number of available permits. `sem_acquire` methods will acquire a permit if available * (reducing the available count by 1) or block if the number of available permits is 0. * \ref sem_release() increases the number of available permits by one potentially unblocking a `sem_acquire` method. * * Note that \ref sem_release() may be called an arbitrary number of times, however the number of available * permits is capped to the max_permit value specified during semaphore initialization. * * Although these semaphore related functions can be used from IRQ handlers, it is obviously preferable to only * release semaphores from within an IRQ handler (i.e. avoid blocking) *//* ... */ #ifdef __cplusplus extern "C" { #endif typedef struct semaphore { struct lock_core core; int16_t permits; int16_t max_permits; ...} semaphore_t; /*! \brief Initialise a semaphore structure * \ingroup sem * * \param sem Pointer to semaphore structure * \param initial_permits How many permits are initially acquired * \param max_permits Total number of permits allowed for this semaphore *//* ... */ void sem_init(semaphore_t *sem, int16_t initial_permits, int16_t max_permits); /*! \brief Return number of available permits on the semaphore * \ingroup sem * * \param sem Pointer to semaphore structure * \return The number of permits available on the semaphore. *//* ... */ int sem_available(semaphore_t *sem); /*! \brief Release a permit on a semaphore * \ingroup sem * * Increases the number of permits by one (unless the number of permits is already at the maximum). * A blocked `sem_acquire` will be released if the number of permits is increased. * * \param sem Pointer to semaphore structure * \return true if the number of permits available was increased. *//* ... */ bool sem_release(semaphore_t *sem); /*! \brief Reset semaphore to a specific number of available permits * \ingroup sem * * Reset value should be from 0 to the max_permits specified in the init function * * \param sem Pointer to semaphore structure * \param permits the new number of available permits *//* ... */ void sem_reset(semaphore_t *sem, int16_t permits); /*! \brief Acquire a permit from the semaphore * \ingroup sem * * This function will block and wait if no permits are available. * * \param sem Pointer to semaphore structure *//* ... */ void sem_acquire_blocking(semaphore_t *sem); /*! \brief Acquire a permit from a semaphore, with timeout * \ingroup sem * * This function will block and wait if no permits are available, until the * defined timeout has been reached. If the timeout is reached the function will * return false, otherwise it will return true. * * \param sem Pointer to semaphore structure * \param timeout_ms Time to wait to acquire the semaphore, in milliseconds. * \return false if timeout reached, true if permit was acquired. *//* ... */ bool sem_acquire_timeout_ms(semaphore_t *sem, uint32_t timeout_ms); /*! \brief Acquire a permit from a semaphore, with timeout * \ingroup sem * * This function will block and wait if no permits are available, until the * defined timeout has been reached. If the timeout is reached the function will * return false, otherwise it will return true. * * \param sem Pointer to semaphore structure * \param timeout_us Time to wait to acquire the semaphore, in microseconds. * \return false if timeout reached, true if permit was acquired. *//* ... */ bool sem_acquire_timeout_us(semaphore_t *sem, uint32_t timeout_us); /*! \brief Wait to acquire a permit from a semaphore until a specific time * \ingroup sem * * This function will block and wait if no permits are available, until the * specified timeout time. If the timeout is reached the function will * return false, otherwise it will return true. * * \param sem Pointer to semaphore structure * \param until The time after which to return if the sem is not available. * \return true if permit was acquired, false if the until time was reached before * acquiring. *//* ... */ bool sem_acquire_block_until(semaphore_t *sem, absolute_time_t until); /*! \brief Attempt to acquire a permit from a semaphore without blocking * \ingroup sem * * This function will return false without blocking if no permits are * available, otherwise it will acquire a permit and return true. * * \param sem Pointer to semaphore structure * \return true if permit was acquired. *//* ... */ bool sem_try_acquire(semaphore_t *sem); #ifdef __cplusplus }extern "C" { ... } #endif/* ... */ #endif
Details
Show:
from
Types: Columns: