dce
2010
ChibiOS/RT
A Real-time OS
BK
TP.HCM
www.chibios.org
by Hoàng Ngọc Tuấn Anh 50700041
and Nguyễn Quang Vinh 50702974
dce
2010
Overview
– Authur : Giovanni Di Sirio.
– ChibiOS/RT (ちびOS/RT) means small Real Time
Operating System.
– Designed for realtime applications.
– Preemptive scheduling.
– 128 priority levels. Multiple threads at the same
priority level are allowed.
– Round Robin scheduling for threads at the same
priority level.
Embedded system
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Overview
• An embedded real time OS which is:
– High portability, compact size, efficient context
switching
– Static architecture
– Dynamic extensions, dynamic object
– Many objects : threads, semaphores, mutexes…
– Support many hardware abstract drivers
– Support architecture: ARM7, ARM Cortex-M0, CortexM3, AVR, MSP430, SMT8…
Embedded system
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Overview
– Programming language : C
– Code size ( compiled) about 5kB ~ 10kB
• Minimal build can reduce code size to about 1,5kB
– Context switch time: 2µS ~ 10µS
– Extensive test suite with benchmarks
Embedded system
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License:
• Multiple licensing options exist for ChibiOS/RT:
– Pure GPL3 license.
• For unstable (alpha, beta…) release
– GPL3 license with Linking Exception.
• For stable release, with exception for closed source app
– Commercial license.
• Features and price see at webpage
• http://chibios.org/dokuwiki/doku.php?id=chibios:commerc
ial
Embedded system
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System state:
Embedded system
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Kernel subsystem
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Version numbers and Indentification
Configuration
Types
Base kernel services
Synchroniztion
Memory Management
I/O support
Registry
Debug
Internals
Embedded system
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Version and Indentification
• Define kernel relate info
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–
#define
_CHIBIOS_RT_
ChibiOS/RT identification macro.
#define
CH_KERNEL_VERSION "2.3.2unstable"
Kernel version string.
#define
CH_KERNEL_MAJOR 2
Kernel version major number.
#define
CH_KERNEL_MINOR 3
Kernel version minor number.
#define
CH_KERNEL_PATCH 2
Kernel version patch number.
Embedded system
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Configuration
• Define kernel settings and hooks
Embedded system
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Types
• Define system types and macros
Embedded system
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Base kernel services
Embedded system
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Base kernel services
• System Management
chSysInit (void)
chSysTimerHandlerI (void)
WORKING_AREA (_idle_thread_wa,
IDLE_THREAD_STACK_SIZE)
_idle_thread (void *p)
Embedded system
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Base kernel services
• Scheduler
_scheduler_init (void)
chSchReadyI (Thread *tp)
chSchGoSleepTimeoutS (tstate_t newstate,
systime_t time)
chSchWakeupS (Thread *ntp, msg_t msg)
chSchDoRescheduleI (void)
chSchRescheduleS (void)
chSchIsRescRequiredExI (void)
Embedded system
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Thread state:
Embedded system
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Base kernel services
• Threads
chThdCreateStatic (void *wsp, size_t size, tprio_t
prio, tfunc_t pf, void *arg)
chThdSetPriority (tprio_t newprio)
chThdResume (Thread *tp)
chThdTerminate (Thread *tp)
chThdSleep (systime_t time)
chThdExit (msg_t msg)
chThdWait (Thread *tp)
Embedded system
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Base kernel services
• Time and Virtual timers
chVTSetI (VirtualTimer *vtp, systime_t time,
vtfunc_t vtfunc, void *par)
chVTResetI (VirtualTimer *vtp)
bool_t chTimeIsWithin (systime_t start, systime_t
end)
Embedded system
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Synchronization
Embedded system
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Counting Semaphores
• Signal: The semaphore counter is increased and if the
result is non-positive then a waiting thread is removed
from the semaphore queue and made ready for
execution.
• Wait: The semaphore counter is decreased and if the
result becomes negative the thread is queued in the
semaphore and suspended.
• Reset: The semaphore counter is reset to a non-negative
value and all the threads in the queue are released.
Embedded system
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Counting Semaphores
•
•
•
•
•
void
void
void
msg_t
msg_t
• void
• void
Embedded system
chSemInit (Semaphore *sp, cnt_t n)
chSemReset (Semaphore *sp, cnt_t n)
chSemResetI (Semaphore *sp, cnt_t n)
chSemWait (Semaphore *sp)
chSemWaitTimeout (Semaphore *sp,
systime_t time)
chSemSignal (Semaphore *sp)
chSemSignalI (Semaphore *sp)
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Counting Semaphores
• msg_t :
– RDY_OK
– RDY_RESET
– RDY_TIMEOUT
• systime_t :
– TIME_IMMEDIATE
– TIME_INFINITE
Embedded system
: immediate timeout
: no timeout
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Binary Semaphores
• Use the existing counting semaphores
• Counter of binary semaphores is not allowed to
grow above the value 1
• Not implement the priority protocol.
• Have only two defined states :
– Taken
– Not taken
Embedded system
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Mutexs Semaphores
• Same as Tkernel
• Defined states :
– Lock
– Unlock
Embedded system
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Events Flag
• Each thread has a mask of pending event flags
inside
• Operations :
– Wait
– Clear
– Signal
– Broadcast
– Dispatch
Embedded system
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2010
Events Flag
• void
chEvtRegisterMask (EventSource *esp,
EventListener *elp, eventmask_t mask)
• void
chEvtUnregister (EventSource *esp,
EventListener *elp)
• eventmask_t chEvtClearFlags (eventmask_t mask)
• void
chEvtSignalFlags (Thread *tp, eventmask_t
mask)
• void
chEvtBroadcastFlags (EventSource *esp,
eventmask_t mask)
• eventmask_t chEvtWaitOne (eventmask_t mask)
Embedded system
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Memory Management
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•
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Core Memory Manager
Heaps
Memory pools
Dynamic threads
Embedded system
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Core Memory Manager
• The core memory manager is a simplified allocator
that only allows to allocate memory blocks
without the possibility to free themMemory pools
Embedded system
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Heap
• malloc()
• free()
Embedded system
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Memory Pools
• allocate/free fixed size objects in constant time
and reliably without memory fragmentation
problems
Embedded system
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I/O Management
• Abstract Sequential Streams
– Can be used as base class for high level object types
such as files, sockets, serial ports, pipes etc.
• Abstract File Streams
• Abstract I/O channels
• I/O queues
– Mostly used in serial-like device drivers
Embedded system
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Registry
• The Threads Registry is a double linked list that
holds all the active threads in the system.
• Thread * chRegFirstThread (void)
• Thread * chRegNextThread (Thread * tp)
• #define REG_REMOVE (tp)
• #define REG_INSERT (tp)
Embedded system
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Debug
• Trace buffer.
• Parameters check.
• Kernel assertions.
Embedded system
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Internals
• Functions manage ThreadsQueue and ThreadsList
• Are not OS APIs
• Should not be directly used in the user
applications code
Embedded system
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