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FreeRTOS Modern C++ Wrappers

License

freertos-mcpp is a C++ wrapper library that allows developers to use the ubiquitous FreeRTOS kernel while simplifying its use by a new API that closely follows the C++ standard classes.

Features

  • No virtual classes, the wrapper classes accurately encapsulate the underlying data structures
  • Promotes static allocation, optimizing RAM use and reducing heap fragmentation risks
  • Public API closely matches the standard C++ thread support library
  • The API selects the threading or interrupt service routine (xFromISR) FreeRTOS API calls by detecting ISR context

Compatibility

  • C++11 and above
  • Tested with FreeRTOS 10, its public API is stable enough to enable the use on a wide range of versions
  • Only works with FreeRTOS ports that have xPortIsInsideInterrupt() call implemented

Porting

This library requires certain configuration values to be set for correct operation. Consider the recommended settings for FreeRTOSConfig.h:

// required globally
#define configSUPPORT_STATIC_ALLOCATION         1

// required to allow termination of threads and automatic resource freeing (see thread documentation)
// and for thread_owner that builds on it
#define configSUPPORT_DYNAMIC_ALLOCATION        1
    extern void vTaskExitHandler(void);
#define configTASK_RETURN_ADDRESS               vTaskExitHandler

// required for thread termination signalling, used by thread::join
// configNUM_THREAD_LOCAL_STORAGE_POINTERS must be higher than configTHREAD_EXIT_CONDITION_INDEX
#define configNUM_THREAD_LOCAL_STORAGE_POINTERS 1
#define configTHREAD_EXIT_CONDITION_INDEX       0

// required to support mutex, timed_mutex
#define configUSE_MUTEXES                       1

// required to support recursive_mutex, recursive_timed_mutex
#define configUSE_RECURSIVE_MUTEXES             1

// required to support counting_semaphore
#define configUSE_COUNTING_SEMAPHORES           1


// recommended to use on Cortex Mx architectures (see src/helpers/runtime_stats_timer.c)
#define configGENERATE_RUN_TIME_STATS           1
    extern void ConfigureTimerForRunTimeStats(void);
#define portCONFIGURE_TIMER_FOR_RUN_TIME_STATS()    ConfigureTimerForRunTimeStats()
    extern uint32_t GetRuntimeCounterValueFromISR(void);
#define portGET_RUN_TIME_COUNTER_VALUE()            GetRuntimeCounterValueFromISR()

In addition to the C++ wrappers, there are helper files located in src/helpers for some common use-cases:

  1. tasks_static.c is required as source to support static allocation of kernel objects
  2. runtime_stats_timer.c is a zero-cost runtime statistics timer for Cortex Mx architectures
  3. malloc_free.c and new_delete_ops.cpp redirect heap allocation to FreeRTOS's heap management