tinySA/docs/ch.txt

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/**
* @mainpage ChibiOS/RT
* @author Giovanni Di Sirio (gdisirio@users.sourceforge.net).
* @section Chibi Chibi ?
* It is the Japanese word for small as in small child. So ChibiOS/RT
* \htmlonly (<span class="t_nihongo_kanji" xml:lang="ja" lang="ja">&#12385;&#12403;</span>OS/RT) \endhtmlonly
* means small Real Time Operating System.
* Source <a href="http://en.wikipedia.org/wiki/Chibi" target="_blank">Wikipedia</a>.
* @section ch_features Features
* <ul>
* <li>Free software, GPL3 licensed.</li>
* <li>Designed for realtime applications.</li>
* <li>Easily portable.</li>
* <li>Mixed programming model:</li>
* <ul>
* <li>Synchronous, using semaphores/mutexes and/or messages.</li>
* <li>Asynchronous, using event sources.</li>
* <li>Mix of the above models, multiple threads listening to multiple event
* sources while serving message queues.</li>
* </ul>
* <li>PC simulator target included, the development can be done on the PC
* using MinGW or VS.
* Timers, I/O channels and other HW resources are simulated in a
* Win32 process and the application code does not need to be aware of it.
* MinGW and VS demos available and ready to go, use them as templates for
* your application.</li>
* <li>Preemptive scheduling.</li>
* <li>128 priority levels.</li>
* <li>Multiple threads at the same priorily level allowed.</li>
* <li>Round robin scheduling for threads at the same priority level.</li>
* <li>Unlimited number of threads.</li>
* <li>Unlimited number of virtual timers.</li>
* <li>Unlimited number of semaphores.</li>
* <li>Unlimited number of mutexes.</li>
* <li>Unlimited number of event sources.</li>
* <li>Unlimited number of messages in queue.</li>
* <li>Unlimited number of I/O queues.</li>
* <li>No static setup at compile time, there is no need to configure a maximum
* number of all the above resources.</li>
* <li>No *need* for a memory allocator, all the kernel structures are static
* and declaratively allocated.</li>
* <li>Threads, Semaphores, Event Sources, Virtual Timers creation/deletion at
* runtime.</li>
* <li>Optional, thread safe, Heap Allocator subsystem.</li>
* <li>Optional, thread safe, Memory Pools Allocator subsystem.</li>
* <li>Blocking and non blocking I/O channels with timeout and events generation
* capability.</li>
* <li>Minimal system requirements: about 8KiB ROM with all options enabled and
* speed optimizations on. The size can shrink under 2KiB by disabling the
* the unused subsystems and optimizing for size.</li>
* <li>Small memory footprint, unused subsystems can be excluded by the
* memory image.</li>
* <li>Almost totally written in C with little ASM code required for ports.</li>
* </ul>
*
* ChibiOS/RT architecture:<br><br>
* @subpage Concepts
*/
/**
* @page Concepts Concepts
* @{
* @section naming Naming Conventions
* ChibiOS/RT APIs are all named following this convention:
* \a ch\<group\>\<action\>\<suffix\>().
* The possible groups are: \a Sys, \a Sch, \a VT, \a Thd, \a Sem, \a Mtx,
* \a Evt, \a Msg, \a IQ, \a OQ, \a HQ,\a FDD, \a HDD, \a Dbg.
* The suffix is not present for normal APIs but can be one of
* the following: "I" for APIs meant to be invoked within the system mutex
* zone, "S" for APIs only useable from within the system mutex zone but not
* from interrupt handlers.<br>
* The APIs without suffix can be invoked only from the user code outsize the
* system mutex zone and not from interrupt handlers unless differently
* specified.<br>
* Examples: \p chThdCreate(), \p chSemSignalI(), \p chIQGetTimeout().
*
* @section scheduling Scheduling
* The strategy is very simple the currently ready thread with the highest
* priority is executed. If more than one thread with equal priority are
* eligible for execution then they are executed in a round-robin way, the
* CPU time slice constant is configurable. The ready list is a double linked
* list of threads ordered by priority.
* @image html readylist.png
* Note that the currently running thread is not in the ready list, the list
* only contains the threads ready to be executed but still actually waiting.
*
* @section states Threads States Diagram
* The image shows how threads can change their state in ChibiOS/RT.<br>
* @image html states.png
*
* @section warea Thread Working Area
* Each thread has its own stack, a Thread structure and a registers dump
* structure. All the structures are allocated into a "Thread working area",
* a thread private heap, usually allocated in a char array declared in your
* code, there is not a central threads table or list, this means you can
* have as many threads you want as long you have enough available RAM
* memory. The threads do not use any memory outside the allocated working
* area.<br>
* @image html workspace.png
* <br>
* Note that the registers dump is only present when the Thread is not
* running, the context switching is done by pushing the registers on the
* stack of the switched-out thread and popping the registers of the
* switched-in thread from its stack.
*
* @section sysmutex System Mutex Zone
* It is the code within the OS that cannot be preempted, this code is
* everything between the \p chSysLock() and \p chSysUnlock() API calls.
* The implementation of the APIs in most cases just enables/disables the
* interrupts. Of course the code in the system mutex zone must be as short
* and efficient possible as it affects the RT performance of the whole
* system. The worst case response time is affected by the longest code
* path in the system mutex zone or interrupt handler.
* @code
* // User code, not critical, preemption possible.
* chSysLock();
* ...
* // System critical code, preemption delayed.
* ...
* chSysUnlock();
* // User code, preemption possible again.
* @endcode
* Applications usually do not need to put code into the system mutex zone
* unless you are implementing device drivers or special synchronization
* primitives, everything else can be implemented by using semaphores,
* mutexes, messages or events.
*/
/** @} */
/**
* @defgroup Ports Ports
* @{
* This section describes the technical details for the various supported
* ChibiOS/RT ports.
*/
/** @} */
/**
* @defgroup ARM7 ARM7TDMI
* @{
* <p>
* The ARM7 port makes some assumptions on the application code organization:
* <ul>
* <li>The \p main() function is invoked in system mode.</li>
* <li>Each thread has a private user/system stack, the system has a single
* interrupt stack where all the interrupts are processed.</li>
* <li>The threads are started in system mode.</li>
* <li>The threads code can run in system mode or user mode, however the
* code running in user mode cannot invoke the ChibiOS/RT APIs directly
* because privileged instructions are used inside.<br>
* The kernel APIs can be eventually invoked by using a SWI entry point
* that handles the switch in system mode and the return in user mode.</li>
* <li>Other modes are not preempt-able because the system code assumes the
* threads running in system mode. When running in supervisor or other
* modes make sure that the interrupts are globally disabled.</li>
* <li>Interrupts nesting is not supported in the ARM7 code because their
* implementation, even if possible, is not really efficient in this
* architecture.</li>
* <li>FIQ sources can preempt the kernel (by design) so it is not possible to
* invoke the kernel APIs from inside a FIQ handler.</li>
* </ul>
* </p>
* <p>
* The ARM7 port is shared by multiple demos targeted to various implementations:
* </p>
* @ingroup Ports
*/
/** @} */
/**
* @defgroup LPC214x LPC214x Support
* @{
* <p>
* The LPC214x support includes:
* <ul>
* <li>VIC support code.</li>
* <li>Buffered, interrupt driven, serial driver.</li>
* <li>SSP driver.</li>
* <li>A MMC/SD demo driver.</li>
* <li>A buzzer demo driver.</li>
* <li>A minimal demo, useful as project template.</li>
* <li>A demo supporting the kernel test suite.</li>
* <li>A C++ demo supporting the kernel test suite.</li>
* </ul>
* </p>
* @ingroup ARM7
*/
/** @} */
/**
* @defgroup AT91SAM7X AT91SAM7X Support
* @{
* <p>
* The AT91SAM7X support includes:
* <ul>
* <li>Buffered, interrupt driven, serial driver.</li>
* <li>A demo supporting the kernel test suite.</li>
* </ul>
* </p>
* @ingroup ARM7
*/
/** @} */
/**
* @defgroup ARMCM3 ARM Cortex-M3
* @{
* <p>
* The ARM Cortex-M3 port is organized as follow:
* </p>
* <ul>
* <li>The \p main() function is invoked in thread-privileged mode.</li>
* <li>Each thread has a private process stack, the system has a single main
* stack where all the interrupts and exceptions are processed.</li>
* <li>Only the 4 MSb of the priority level are used, the 4 LSb are assumed
* to be zero.</li>
* <li>The threads are started in thread-privileged mode with BASEPRI level
* 0x00 (disabled).</li>
* <li>The kernel raises its BASEPRI level to 0x10 in order to protect the
* system mutex zones. Note that exceptions with level 0x00 can preempt
* the kernel, such exception handlers cannot invoke kernel APIs directly.</li>
* <li>Interrupt nesting and the other advanced NVIC features are supported.</li>
* <li>The SVC instruction and vector, with parameter #0, is internally used
* for commanded context switching.<br>
* It is possible to share the SVC handler at the cost of slower context
* switching.</li>
* <li>The PendSV vector is internally used for preemption context switching.</li>
* </ul>
* @ingroup Ports
*/
/** @} */
/**
* @defgroup STM32F103 STM32F103 Support
* @{
* <p>
* The STM32F103 support includes:
* <ul>
* <li>Buffered, interrupt driven, serial driver.</li>
* <li>A demo supporting the kernel test suite.</li>
* </ul>
* </p>
* @ingroup ARMCM3
*/
/** @} */
/**
* @defgroup AVR MegaAVR
* @{
* <p>
* Notes about the AVR port:
* </p>
* <ul>
* <li>The AVR does not have a dedicated interrupt stack, make sure to reserve
* enough stack space for interrupts in each thread stack. This can be done
* by modifying the \p INT_REQUIRED_STACK macro into \p ports/AVR/chcore.h.</li>
* </ul>
* @ingroup Ports
*/
/** @} */
/**
* @defgroup MSP430 MSP430
* @{
* <p>
* Notes about the MSP430 port:
* </p>
* <ul>
* <li>In the current version the MSP430 port is still untested.</li>
* <li>The MSP430 does not have a dedicated interrupt stack, make sure to reserve
* enough stack space for interrupts in each thread stack. This can be done
* by modifying the \p INT_REQUIRED_STACK macro into \p ports/MSP430/chcore.h.</li>
* </ul>
* @ingroup Ports
*/
/** @} */
/**
* @defgroup Kernel Kernel
* @{
*/
/** @} */
/**
* @defgroup Config Configuration
* @{
* In \p chconf.h are defined the required subsystems for your application.
* @ingroup Kernel
* @file chconf.h ChibiOS/RT configuration file.
*/
/** @} */
/**
* @defgroup Core Core
* @{
* Non portable code.
* @ingroup Kernel
* @file chcore.c Non portable code.
*/
/** @} */
/**
* @defgroup Initialization Initialization
* @{
* Initialization APIs and procedures.
* @ingroup Kernel
* @file ch.h ChibiOS/RT main include file, it includes everything else.
* @file chinit.c ChibiOS/RT Initialization code.
*/
/** @} */
/**
* @defgroup Debug Debug
* @{
* Debug APIs and procedures.
* @ingroup Kernel
* @file debug.h Debug macros and structures.
* @file chdebug.c ChibiOS/RT Debug code.
*/
/** @} */
/**
* @defgroup Scheduler Scheduler
* @{
* ChibiOS/RT scheduler.
* @ingroup Kernel
* @file chschd.c Scheduler code.
* @file scheduler.h Scheduler macros and structures.
*/
/** @} */
/**
* @defgroup ThreadLists Thread Lists and Queues
* @{
* ChibiOS/RT thread lists and queues utilities.
* @ingroup Kernel
* @file chlists.c Lists and queues code.
* @file lists.h Lists and queues macros and structures.
*/
/** @} */
/**
* @defgroup Threads Threads
* @{
* Threads creation and termination APIs.
* @file threads.h Threads structures, macros and functions.
* @file chthreads.c Threads code.
*/
/** @} */
/**
* @defgroup VirtualTimers Virtual Timers
* @{
* Virtual Timers APIs.
* @file src/chdelta.c Virtual Timers code.
* @file delta.h Virtual Timers macros and structures.
*/
/** @} */
/**
* @defgroup Time Time
* @{
* Time related APIs.
* @file include/sleep.h Time macros and structures.
* @file chsleep.c Time functions.
*/
/** @} */
/**
* @defgroup Heap Heap
* @{
* Heap Allocator related APIs.
* <b>Operation mode</b><br><br>
* The heap allocator implements a first-fit strategy and its APIs are
* functionally equivalent to the usual \p malloc() and \p free(). The main
* difference is that the heap APIs are thread safe.<br>
* By enabling the \p CH_USE_MALLOC_HEAP option the heap manager will use the
* runtime-provided \p malloc() and \p free() as backend for the heap APIs
* instead of the system provided allocator.<br>
* In order to use the heap APIs the \p CH_USE_HEAP option must be specified
* in \p chconf.h.
* @file include/heap.h Heap macros and structures.
* @file chheap.c Heap functions.
*/
/** @} */
/**
* @defgroup MemoryPools Memory Pools
* @{
* Memory Pools related APIs.
* <b>Operation mode</b><br><br>
* The Memory Pools APIs allow to allocate/free fixed size objects in
* <b>constant time</b> and reliably without memory fragmentation problems.<br>
* In order to use the Time APIs the \p CH_USE_MEMPOOLS option must be
* specified in \p chconf.h.
* @file include/mempools.h Memory Pools macros and structures.
* @file chmempools.c Memory Pools functions.
*/
/** @} */
/**
* @defgroup Semaphores Semaphores
* @{
* Semaphores and threads synchronization.
* <b>Operation mode</b><br><br>
* A semaphore is a threads synchronization object, some operations
* are defined on semaphores:<br>
* <ul>
* <li><b>Signal</b>: 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.
* </li>
* <li><b>Wait</b>: The semaphore counter is decreased and if the result
* becomes negative the thread is queued in the semaphore and suspended.
* </li>
* <li><b>Reset</b>: The semaphore counter is reset to a non-negative value
* and all the threads in the queue are released.
* </li>
* </ul>
* Semaphores can be used as guards for mutual exclusion code zones but
* also have other uses, queues guards and counters as example.<br>
* In order to use the Semaphores APIs the \p CH_USE_SEMAPHORES
* option must be specified in \p chconf.h.<br><br>
* @file semaphores.h Semaphores macros and structures.
* @file chsem.c Semaphores code.
*/
/** @} */
/**
* @defgroup Mutexes Mutexes
* @{
* Mutexes and threads synchronization.
* <b>Operation mode</b><br><br>
* A mutex is a threads synchronization object, some operations are defined
* on mutexes:<br>
* <ul>
* <li><b>Lock</b>: The mutex is checked, if the mutex is not owned by some
* other thread then it is locked else the current thread is queued on the
* mutex in a list ordered by priority.
* </li>
* <li><b>Unlock</b>: The mutex is released by the owner and the highest
* priority thread waiting in the queue, if any, is resumed and made owner
* of the mutex.
* </li>
* </ul>
* In order to use the Event APIs the \p CH_USE_MUTEXES option must be
* specified in \p chconf.h.<br>
*
* <b>Constraints</b><br><br>
* In ChibiOS/RT the Unlock operations are always performed in Lock-reverse
* order. The Unlock API does not even have a parameter, the mutex to unlock
* is taken from an internal stack of owned mutexes.
* This both improves the performance and is required by the priority
* inheritance mechanism.
*
* <b>The priority inversion problem</b><br><br>
* The mutexes in ChibiOS/RT implements the <b>full</b> priority
* inheritance mechanism in order handle the priority inversion problem.<br>
* When a thread is queued on a mutex, any thread, directly or indirectly,
* holding the mutex gains the same priority of the waiting thread (if their
* priority was not already equal or higher). The mechanism works with any
* number of nested mutexes and any number of involved threads. The algorithm
* complexity (worst case) is N with N equal to the number of nested mutexes.
* @file mutexes.h Mutexes macros and structures.
* @file chmtx.c Mutexes functions.
*/
/** @} */
/**
* @defgroup Events Events
* @{
* Event Sources and Event Listeners.<br>
* <b>Operation mode</b><br><br>
* An Event Source is a special object that can be signaled by a thread or
* an interrupt service routine. Signaling an Event Source has the effect
* that all the threads registered on the Event Source will receive
* and serve the event.<br>
* An unlimited number of Event Sources can exists in a system and each
* thread can listen on an unlimited number of them.<br>
* Note that the events can be asynchronously generated but are synchronously
* served, a thread can serve event by calling the \p chEvtWait()
* API. If an event is generated while a listening thread is not ready to
* serve it then the event becomes "pending" and will be served as soon the
* thread invokes the \p chEvtWait().<br>
* In order to use the Event APIs the \p CH_USE_EVENTS option must be
* specified in \p chconf.h.
* @file events.h Events macros and structures.
* @file chevents.c Events functions.
*/
/** @} */
/**
* @defgroup Messages Messages
* @{
* Synchronous Messages.<br>
* <b>Operation Mode</b><br><br>
* Messages are an easy to use and fast IPC mechanism, threads can both serve
* messages and send messages to other threads, the mechanism allows data to
* be carryed in both directions. Data is not copyed between the client and
* server threads but just a pointer passed so the exchange is very time
* efficient.<br>
* Messages are usually processed in FIFO order but it is possible to process
* them in priority order by specifying CH_USE_MESSAGES_PRIORITY
* in \p chconf.h.<br>
* Threads do not need to allocate space for message queues, the mechanism
* just requires two extra pointers in the \p Thread structure (the message
* queue header).<br>
* In order to use the Messages APIs the \p CH_USE_MESSAGES option must be
* specified in \p chconf.h.
* @file messages.h Messages macros and structures.
* @file chmsg.c Messages functions.
*/
/** @} */
/**
* @defgroup IOQueues I/O Queues
* @{
* ChibiOS/RT supports several kinds of queues. The queues are mostly used
* in serial-like device drivers. The device drivers are usually designed to
* have a lower side (lower driver, it is usually an interrupt service
* routine) and an upper side (upper driver, accessed by the application
* threads).<br>
* There are several kind of queues:<br>
* <ul>
* <li><b>Input queue</b>, monodirectional queue where the writer is the
* lower side and the reader is the upper side.</li>
* <li><b>Output queue</b>, monodirectional queue where the writer is the
* upper side and the reader is the lower side.</li>
* <li><b>Half duplex queue</b>, bidirectional queue where the buffer is shared
* between a receive and a transmit queues. This means that concurrent
* buffered input and output operations are not possible, this is perfectly
* acceptable for a lot of applications however, as example an RS485 driver.
* <li><b>Full duplex queue</b>, bidirectional queue where read and write
* operations can happen at the same time. Full duplex queues
* are implemented by pairing an input queue and an output queue together.
* </ul>
* In order to use the I/O queues the \p CH_USE_QUEUES option must
* be specified in \p chconf.h.<br>
* In order to use the half duplex queues the \p CH_USE_QUEUES_HALFDUPLEX
* option must be specified in \p chconf.h.
* @file queues.h I/O Queues macros and structures.
* @file chqueues.c I/O Queues code.
*/
/** @} */
/**
* @defgroup Serial Serial Drivers
* @{
* This module implements a generic full duplex serial driver and a generic
* half duplex serial driver. It uses the I/O Queues for communication between
* the upper and the lower driver and events to notify the application about
* incoming data, outcoming data and other I/O events.
* The module also contains functions that make the implementation of the
* interrupt service routines much easier.<br>
* In order to use the serial full duplex driver the
* \p CH_USE_SERIAL_FULLDUPLEX option must be specified in \p chconf.h.<br>
* In order to use the serial half duplex driver the
* \p CH_USE_SERIAL_HALFDUPLEX option must be specified in \p chconf.h.
* @file serial.h Serial Drivers macros and structures.
* @file chserial.c Serial Drivers code.
*/
/** @} */
/**
* @defgroup CPlusPlusLibrary C++ Wrapper
* @{
* C++ wrapper module. This module allows to use the ChibiOS/RT functionalities
* from C++ as classes and objects rather the traditional "C" APIs.
* @file ch.hpp C++ wrapper classes and definitions.
* @file ch.cpp C++ wrapper code.
*/
/** @} */