/** * @mainpage ChibiOS/RT * @author Giovanni Di Sirio (gdisirio@users.sourceforge.net). * *

Chibi ?

* I didn't want a serious name for this project. It is the Japanese word for * small as in small child. So ChibiOS/RT * @htmlonly (ちびOS/RT) @endhtmlonly * means small Real Time Operating System. * Source Wikipedia. *

Features

* - Free software, GPL3 licensed. * - Designed for realtime applications. * - Easily portable. * - Mixed programming model: * - Synchronous, using semaphores/mutexes/condvars and/or messages. * - Asynchronous, using event sources. * - Mix of the above models, multiple threads listening to multiple event * sources while serving message queues. * - PC simulator target included, the development can be done on the PC * using MinGW.
* 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 demo available. * - Preemptive scheduling. * - 128 priority levels. * - Multiple threads at the same priority level allowed. * - Round robin scheduling for threads at the same priority level. * - Unlimited number of threads. * - Unlimited number of virtual timers. * - Unlimited number of semaphores. * - Unlimited number of mutexes. * - Unlimited number of condvars. * - Unlimited number of event sources. * - Unlimited number of messages in queue. * - Unlimited number of I/O queues. * - No static setup at compile time, there is no need to configure a maximum * number of all the above resources. * - No *need* for a memory allocator, all the kernel structures are static * and declaratively allocated. * - Threads, Semaphores, Event Sources, Virtual Timers creation/deletion at * runtime. * - Optional, thread safe, Heap Allocator subsystem. * - Optional, thread safe, Memory Pools Allocator subsystem. * - Blocking and non blocking I/O channels with timeout and events generation * capability. * - 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. * - Small memory footprint, unused subsystems can be excluded by the * memory image. * - Almost totally written in C with little ASM code required for ports. * *

Related pages

* - @subpage Concepts * - @subpage Articles */ /** * @page Concepts Concepts * @{ * @brief ChibiOS/RT Concepts and Architecture * @section naming Naming Conventions * ChibiOS/RT APIs are all named following this convention: * @a ch\\\(). * The possible groups are: @a Sys, @a Sch, @a VT, @a Thd, @a Sem, @a Mtx, * @a Cond, @a Evt, @a Msg, @a IQ, @a OQ, @a HQ, @a FDD, @a HDD, @a Dbg, * @a Heap, @a Pool. * * @section api_suffixes API Names Suffixes * The suffix can be one of the following: * - None, APIs without any suffix can be invoked only from the user * code in the Normal state unless differently specified. See * @ref system_states. * - "I", I-Class APIs are invokable only from the I-Locked or * S-Locked states. See @ref system_states. * - "S", S-Class APIs are invokable only from the S-Locked * state. See @ref system_states. * Examples: @p chThdCreateStatic(), @p chSemSignalI(), @p chIQGetTimeout(). * * @section interrupt_classes Interrupt Classes * In ChibiOS/RT there are three logical interrupt classes: * - Regular Interrupts. Maskable interrupt sources that cannot * preempt the kernel code and are thus able to invoke operating system APIs * from within their handlers. The interrupt handlers belonging to this class * must be written following some rules. See the @ref System APIs group and * @ref article_interrupts. * - Fast Interrupts. Maskable interrupt sources with the ability * to preempt the kernel code and thus have a lower latency and are less * subject to jitter, see @ref article_jitter. Such sources are not * supported on all the architectures.
* Fast interrupts are not allowed to invoke any operating system API from * within their handlers. Fast interrupt sources may however pend a lower * priority regular interrupt where access to the operating system is * possible. * - Non Maskable Interrupts. Non maskable interrupt sources are * totally out of the operating system control and have the lowest latency. * Such sources are not supported on all the architectures. * * The mapping of the above logical classes into physical interrupts priorities * is, of course, port dependent. See the documentation of the various ports * for details. * * @section system_states System States * When using ChibiOS/RT the system can be in one of the following logical * operating states: * - Init. When the system is in this state all the maskable * interrupt sources are disabled. In this state it is not possible to use * any system API except @p chSysInit(). This state is entered after a * physical reset. * - Normal. All the interrupt sources are enabled and the system APIs * are accessible, threads are running. * - Suspended. In this state the fast interrupt sources are enabled but * the regular interrupt sources are not. In this state it is not possible * to use any system API except @p chSysDisable() or @p chSysEnable() in * order to change state. * - Disabled. When the system is in this state both the maskable * regular and fast interrupt sources are disabled. In this state it is not * possible to use any system API except @p chSysSuspend() or * @p chSysEnable() in order to change state. * - Sleep. Architecture-dependent low power mode, the idle thread * goes in this state and waits for interrupts, after servicing the interrupt * the Normal state is restored and the scheduler has a chance to reschedule. * - S-Locked. Kernel locked and regular interrupt sources disabled. * Fast interrupt sources are enabled. S-Class and I-Class APIs are * invokable in this state. * - I-Locked. Kernel locked and regular interrupt sources disabled. * I-Class APIs are invokable from this state. * - Serving Regular Interrupt. No system APIs are accessible but it is * possible to switch to the I-Locked state using @p chSysLockFromIsr() and * then invoke any I-Class API. Interrupt handlers can be preemptable on some * architectures thus is important to switch to I-Locked state before * invoking system APIs. * - Serving Fast Interrupt. System APIs are not accessible. * - Serving Non-Maskable Interrupt. System APIs are not accessible. * - Halted. All interrupt sources are disabled and system stopped into * an infinite loop. This state can be reached if the debug mode is activated * and an error is detected or after explicitly invoking * @p chSysHalt(). * * Note that the above state are just Logical States that may have no * real associated machine state on some architectures. The following diagram * shows the possible transitions between the states: * * @dot digraph example { rankdir="LR"; node [shape=circle, fontname=Helvetica, fontsize=8, fixedsize="true", width="0.75", height="0.75"]; edge [fontname=Helvetica, fontsize=8]; init [label="Init", style="bold"]; norm [label="Normal", shape=doublecircle]; susp [label="Suspended"]; disab [label="Disabled"]; slock [label="S-Locked"]; ilock [label="I-Locked"]; slock [label="S-Locked"]; sleep [label="Sleep"]; sri [label="SRI"]; init -> norm [label="chSysInit()"]; norm -> slock [label="chSysLock()", constraint=false]; slock -> norm [label="chSysUnlock()"]; norm -> susp [label="chSysSuspend()"]; susp -> disab [label="chSysDisable()"]; norm -> disab [label="chSysDisable()"]; susp -> norm [label="chSysEnable()"]; disab -> norm [label="chSysEnable()"]; slock -> ilock [label="Context Switch", dir="both"]; norm -> sri [label="Regular IRQ", style="dotted"]; sri -> norm [label="Regular IRQ return", fontname=Helvetica, fontsize=8]; sri -> ilock [label="chSysLockFromIsr()", constraint=false]; ilock -> sri [label="chSysUnlockFromIsr()", fontsize=8]; norm -> sleep [label="Idle Thread"]; sleep -> sri [label="Regular IRQ", style="dotted"]; } * @enddot * Note, the SFI, Halted and SNMI states were not shown * because those are reachable from most states: * * @dot digraph example { rankdir="LR"; node [shape=circle, fontname=Helvetica, fontsize=8, fixedsize="true", width="0.75", height="0.75"]; edge [fontname=Helvetica, fontsize=8]; any1 [label="Any State\nexcept *"]; any2 [label="Any State"]; sfi [label="SFI"]; halt [label="Halted"]; SNMI [label="SNMI"]; any1 -> sfi [style="dotted", label="Fast IRQ"]; sfi -> any1 [label="Fast IRQ return"]; any2 -> halt [label="chSysHalt()"]; any2 -> SNMI [label="Synchronous NMI"]; any2 -> SNMI [label="Asynchronous NMI", style="dotted"]; SNMI -> any2 [label="NMI return"]; halt -> SNMI [label="Asynchronous NMI", style="dotted"]; SNMI -> halt [label="NMI return"]; } * @enddot * @attention * except: Init, Halt, SNMI, Disabled. * * @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 thread_states Threads States * The image shows how threads can change their state in ChibiOS/RT.
* @dot digraph example { /*rankdir="LR";*/ node [shape=circle, fontname=Helvetica, fontsize=8, fixedsize="true", width="0.75", height="0.75"]; edge [fontname=Helvetica, fontsize=8]; start [label="Start", style="bold"]; run [label="Running"]; ready [label="Ready"]; suspend [label="Suspended"]; sleep [label="Sleeping"]; stop [label="Stop", style="bold"]; start -> suspend [label="chThdInit()", constraint=false]; start -> run [label="chThdCreate()"]; start -> ready [label="chThdCreate()"]; run -> ready [label="Reschedulation", dir="both"]; suspend -> run [label="chThdResume()"]; suspend -> ready [label="chThdResume()"]; run -> sleep [label="chSchGoSleepS()"]; sleep -> run [label="chSchWakepS()"]; sleep -> ready [label="chSchWakepS()"]; run -> stop [label="chThdExit()"]; } * @enddot * * @section priority Priority Levels * Priorities in ChibiOS/RT are a contiguous numerical range but the initial * and final values are not enforced.
* The following table describes the various priority boundaries (from lowest * to highest): * - @p IDLEPRIO, this is the lowest priority level and is reserved for the * idle thread, no other threads should share this priority level. This is * the lowest numerical value of the priorities space. * - @p LOWPRIO, the lowest priority level that can be assigned to an user * thread. * - @p NORMALPRIO, this is the central priority level for user threads. It is * advisable to assign priorities to threads as values relative to * @p NORMALPRIO, as example NORMALPRIO-1 or NORMALPRIO+4, this ensures the * portability of code should the numerical range change in future * implementations. * - @p HIGHPRIO, the highest priority level that can be assigned to an user * thread. * - @p ABSPRO, absolute maximum software priority level, it can be higher than * @p HIGHPRIO but the numerical values above @p HIGHPRIO up to @p ABSPRIO * (inclusive) are reserved. This is the highest numerical value of the * priorities space. * * @section warea Thread Working Area * Each thread has its own stack, a Thread structure and some preemption * areas. All the structures are allocated into a "Thread Working Area", * a thread private heap, usually statically declared in your code. * Threads do not use any memory outside the allocated working area * except when accessing static shared data.

* @image html workspace.png *
* Note that the preemption area is only present when the thread is not * running (switched out), 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. * The preemption area can be divided in up to three structures: * - External Context. * - Interrupt Stack. * - Internal Context. * * See the @ref Core documentation for details, the area may change on * the various ports and some structures may not be present (or be zero-sized). */ /** @} */ /** * @page Articles Articles * @{ * ChibiOS/RT Articles and Code Examples: * - @subpage article_atomic * - @subpage article_saveram * - @subpage article_interrupts * - @subpage article_jitter * - @subpage article_timing */ /** @} */ /** * @defgroup Ports Ports * @{ * This section describes the technical details for the various supported * ChibiOS/RT ports. */ /** @} */ /** * @defgroup Kernel Kernel * @{ * @file ch.h ChibiOS/RT main include file, it includes everything else. */ /** @} */ /** * @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 Generic Port Code Templates * @{ * Non portable code templates. * @ingroup Kernel * @file src/templates/chcore.c Non portable code template file. * @file src/templates/chcore.h Non portable macros and structures template file. */ /** @} */ /** * @defgroup Types Types * @{ * System types and macros. * @ingroup Kernel * @file templates/chtypes.h System types and code modifiers. */ /** @} */ /** * @defgroup System System Management * @{ * Initialization, Locks, Interrupt Handling, Power Management, Abnormal * Termination. * @ingroup Kernel * @file sys.h System related macros and structures. * @file chsys.c System related code. */ /** @} */ /** * @defgroup Inline Inline * @{ * System inline-able code. * @ingroup Kernel * @file inline.h Inline versions of some critical system routines. */ /** @} */ /** * @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 Time Time and Virtual Timers * @{ * Time and Virtual Timers related APIs. * @file include/vt.h Time macros and structures. * @file chvt.c Time functions. */ /** @} */ /** * @defgroup Heap Heap * @{ * Heap Allocator related APIs. *

Operation mode

* 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.
* 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.
* 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. *

Operation mode

* The Memory Pools APIs allow to allocate/free fixed size objects in * constant time and reliably without memory fragmentation problems.
* 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. *

Operation mode

* A semaphore is a threads synchronization object, some operations * are defined on 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. * Semaphores can be used as guards for mutual exclusion code zones but * also have other uses, queues guards and counters as example.
* In order to use the Semaphores APIs the @p CH_USE_SEMAPHORES * option must be specified in @p chconf.h.

* @file semaphores.h Semaphores macros and structures. * @file chsem.c Semaphores code. */ /** @} */ /** * @defgroup Mutexes Mutexes * @{ * Mutexes and threads synchronization. *

Operation mode

* A mutex is a threads synchronization object, some operations are defined * on mutexes: * - Lock: 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. * - Unlock: 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. * In order to use the Event APIs the @p CH_USE_MUTEXES option must be * specified in @p chconf.h.
* *

Constraints

* 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. * *

The priority inversion problem

* The mutexes in ChibiOS/RT implements the full priority * inheritance mechanism in order handle the priority inversion problem.
* 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 CondVars Conditional Variables * @{ * Conditional Variables and threads synchronization. *

Operation mode

* The condition variable is a synchronization object meant to be used inside * a zone protected by a @p Mutex. Mutexes and CondVars together can implement * a Monitor construct.
* In order to use the Conditional Variables APIs the @p CH_USE_CONDVARS * option must be specified in @p chconf.h.

* @file condvars.h Conditional Variables macros and structures. * @file chcond.c Conditional Variables code. */ /** @} */ /** * @defgroup Events Events * @{ * Event Sources and Event Listeners. *

Operation mode

* 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.
* An unlimited number of Event Sources can exists in a system and each * thread can listen on an unlimited number of them.
* Note that the events can be asynchronously generated but are synchronously * served, a thread can serve event by calling a @p chEvtWaitXXX() * 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 a @p chEvtWaitXXX().
* 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 inter-thread Messages. *

Operation Mode

* 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 carried in both directions. Data is not copied between the client and * server threads but just a pointer passed so the exchange is very time * efficient.
* 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.
* 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).
* 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).
* There are several kind of queues:
* - Input queue, unidirectional queue where the writer is the * lower side and the reader is the upper side. * - Output queue, unidirectional queue where the writer is the * upper side and the reader is the lower side. * - Half duplex queue, 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. * - Full duplex queue, 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. * In order to use the I/O queues the @p CH_USE_QUEUES option must * be specified in @p chconf.h.
* 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.
* In order to use the serial full duplex driver the * @p CH_USE_SERIAL_FULLDUPLEX option must be specified in @p chconf.h.
* 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 utilities_library Utilities Library * @{ * @brief Utilities Library. * @details This is a collection of useful library code that is not part of * the base kernel services. *

Notes

* The library code does not follow the same naming convention of the * system APIs in order to make very clear that it is not "core" code.
* The main difference is that library code is not formally tested in the * test suite but through usage in the various demo application. */ /** @} */ /** * @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. * * @ingroup utilities_library * @file ch.hpp C++ wrapper classes and definitions. * @file ch.cpp C++ wrapper code. */ /** @} */ /** * @defgroup event_timer Events Generator Timer * @{ * @brief Event Generator Timer. * @details This timer generates an event at regular intervals. The * listening threads can use the event to perform time related activities. * Multiple threads can listen to the same timer. * * @ingroup utilities_library * @file evtimer.c Events Generator Timer code. * @file evtimer.h Events Generator Timer structures and macros. */ /** @} */