Release notes embOS version 3.40c1 for ARM and ARM Developer Suite

  1. Tool chain used for build
  2. New features
  3. Improvements
  4. Program corrections
  5. Known problems
  6. Release history
  7. Miscellaneous

Tool chain used for build

The following tools have been used:

Compiler:  ARM C Compiler, ADS1.2 [Build 848]
           Thumb C Compiler, ADS1.2 [Build 848]
Assembler: ARM/Thumb Macro Assembler, ADS1.2 [Build 848]
Librarian: ARM Archiver, ADS1.2 [Build 848]
Workbench: CodeWarrior IDE version

New features

Version 3.40c1

  1. ATMEL AT91SAM7S supported
    embOS for ARM ADS now comes with start projects for the ATMEL ATSAM7S CPUs.
    The start projects are prepared for the ATMEL EK-boards and can be downloaded and be debugged using J-Link with RDI.
  2. ATMEL AT91SAMA3 supported
    embOS for ARM ADS now comes with a start project for the ATMEL ATSAM7A3 CPU
    The start project is prepared for the ATMEL EK-board and can be downloaded and be debugged using J-Link with RDI.

Version 3.40c

  1. OS_Yield() may suspend a task unconditionally
    When tasks are running on round robin with timeslice, the function OS_Yield() can be used to end the timeslice of the running task immediately and activate an other task with the same priority which is ready for execution. The function has no effect on tasks that are not running on round robin.

Version 3.40

  1. Task switch time can be measured by application
    embOS now comes with sample applications which allow accurate measurement of task switch time in a running application.

Version 3.32o

  1. Automatic call of OS_INIT_SYS_LOCKS() removed.
    During initialization of embOS, OS_INIT_SYS_LOCK() is not called automatically.
    As most of the applications do not need thread safe system libraries, an automatic activation of syslocks causes unwanted overhead.
    If supported and required, the user may call OS_INIT_SYS_LOCKS() from his own application after normal initialization of embOS.

Version 3.32m

  1. OS_TimerEx, Extended timer implemented
    Extended timers are software timers which call a user defined callback function when the timer expires.
    In comparison to normal em The parameter value is initialized during timer creation.

Version 3.32j

  1. OS_CSemaRequest implemented
    May be used to decrement a counting semaphore conditionally, if a signal is available.
    The function never blocks the calling task and delivers a result which indicates whether the semaphore was available.

Version 3.32f

  1. OS_INIT_SYS_LOCKS() implemented
    May be used to include initialization code for thread safe system libraries.

Version 3.32d

  1. OS_Q_GetPtrTimed() implemented
    New queue retrieval function which waits for a message with specified timeout.

Version 3.32c

  1. OS_EVENT_WaitTimed() implemented
    New event object function to wait for an event with a timeout limit.

Version 3.32b

  1. Task context modified for debug builds
    The number of task activations is now part of the task context in debug builds.
    The number of activations are therefore displayed in the task list window of embOS plugin, when an embOS debug library is used.
    Previous versions of embOS showed this information in profiling builds only.

Version 3.32a

  1. A parameter may be passed to a task function
    Using the new embOS functions OS_CREATETASK_EX() or OS_CreateTaskEx() allows to pass a void pointer as parameter to a task.

Version 3.32

  1. Event objects introduced
    Event objects are standalone objects which are not assigned to a specific task.
    Event objects may be used to synchronize one or multiple task to a specific event.
    Events can be triggered from a task, a timer, or an interrupt handler.

Version 3.30b

  1. OKI 69L6203 supported
    embOS now comes with a sample project for OKI L69Q6203 series CPUs which runs on ML69Q6203 CPU Board.
    The project is prepared for debugging with J-Link in RAM.

Version 3.30a

  1. embOS internal time handling modified to allow long delays
    For 8- and 16-bit CPUs the maximum range for delays and timer periods is limited to 32767 embOS timer ticks, because time comparison ist done by integer calculation.
    By recompiling sources with datatype OS_TIME defined as signed long, longer delays and timer periods up to 2147483647 ticks can be realized.
    The embOS libraries of object versions for 8- and 16-bit CPUs are still delivered with the limitation to 32767 timer ticks.

Version 3.28p

  1. New error handling for version without round robin scheduling
    In debug versions of embOS, OS_Error() is called with error code OS_ERR_TASK_PRIORITY, if a task is created with a priority which is already assigned to an other task.
    OS_Error() is also called with the same errorcode, if a task priority is assigned by call of OS_SetPriority() and the new pririty is already assigned to an other task.
    Round robin switching can be disabled by recompiling sources with OS_RR_SUPPORTED defined as 0.

Version 3.28l

  1. OS_SignalCSemaMax()
    New counting semaphore handling function which specifies a maximum count value.
    This allows counting semaphores used as binary semaphores.

Version 3.28i

  1. OS_DeleteRSema()
    New resource semaphore handling function allows to delete resource semaphores during runtime.

Version 3.28h

  1. Additional error checks in debug builds of embOS
    OS_CreateRSema() now generates an error, when the addressed resource semaphore was already created before.
    OS_CreateCSema() now generates an error, when the addressed counting semaphore was already created before.
    OS_CreateMB() now generates an error, when the mailbox was already created before.
    OS_CreateTimer() now generates an error, when the software timer was already created before.
    OS_MEMF_Create() now generates an error, when the addressed fixed size memory pool was already created before.

Version 3.28g

  1. OS_GetSuspendCnt()
    New info function to examine suspension state and count of a task.

Version 3.26

  1. OS_Terminate() modified
    Task may be terminated anytime, regardless of task state.
    All resources claimed by the terminated task are automatically released.

Version 3.22a

  1. OS_PutMailFront() / OS_PutMailFront1
    New mailbox functions to enable LIFO behavior of mailboxes.
  2. OS_PutMailFrontCond() / OS_PutMailFrontCond1()
    New conditional mailbox functions to enable LIFO behavior of mailboxes.

Version 3.20

  1. OS_Suspend() / OS_Resume() implemented
    New functions to suspend and resume tasks unconditionally.
  2. Fixed size memory blocks implemeted
    New functions to allocate fixed size memory blocks from embOS.
  3. Dynamic memory allocation supported by embOS
    Thread safe dynamic memory allocation functions implemented.

Version 3.10l

    1st version for ARM using ADS


Version 3.40b

  1. Queue management improved.
    For some CPUs, the buffer start address for Queues has to be aligned. Now embOS automatically corrects the alignment, if required.

Version 3.40a

  1. Counting semaphores improved.
    The counters of counting semaphores are now integer values.
    Error handling is also improved. When a counting semaphore overflows, the embOS error handler OS_Error() is called in debug builds.

Version 3.40

  1. Task switch time improved.
    Scheduling optimized to improve task switch time.
  2. Task switch time improved for task events.
    Task event handling modified to improve task switch time for tasks waiting on events.
  3. Interrupt latency improved.
    During task switch, the time period when interrupts are disabled is reduced.
  4. embOS timer tick handler improved.
    The standard timer tick handler run faster now. The embOS internal time variable is incremented by 1 on every timer tick.
    When different increments are required, the new timer tick handler OS_HandleTick_Ex(), OS_TickHandler_Ex() or OS_HandleTickDI_Ex() have to be used by application.
    Different inctrements may be configured by a call of OS_CONFIG().

Version 3.32i

  1. Task switch to OS_Idle() modified.
    The call of OS_Idle() from OS_ChangeTask can be overwritten (inhibited) by defining the macro OS_IDLE() which is norammly defined as OS_Idle().
    This allows task switching via an exception for specific CPU/compiler versions.

Version 3.32g

  1. Pointer comparison improved for fixed size memory pools (OS_MEMF module).
    Some compiler produced wrong pointer comparison code in far memory model.
    For specific CPU/compiler versions, the new OS_POINTER_TO_VALUE() function was inroduced to deliver correct results in pointer comparison.

Version 3.28n

  1. embOS round-robin scheduling may be disabled.
    Round-robin scheduling may be disabled by recompiling sources with OS_RR_SUPPORTED defined as 0.
    This will save some bytes of RAM and ROM and may make sense for small CPUs.

Version 3.28g

  1. embOS scheduling simplified
    Task activation and deactivation on "waitable objects" as mailboxes, semaphores, events, fixed size memory blocks now all use the same scheduling method.
    This modification saves ROM and RAM and makes scheduler easier to understand and to maintain.
    Applications which accessed internal data structures of waitable objects directly have to be modified.

Version 3.10l

    1st version for ARM using ADS1.2

Program corrections

Version 3.32o

  1. OS_Unuse() corrected
    OS_Unuse() must not be called from a task that does not claim the resource semaphore.
    According to the documentation, the debug build of embOS should generate a call to OS_Error() if this fault happens.
    All previous versions of embOS did not call OS_Error(). Now, OS_Error() will be called in that situation with error code 156: OS_ERR_RESOURCE_OWNER().

Version 3.32l

  1. OS_EVENT_Delete() corrected
    OS_EVENT_Delete() did not work correctly. OS_LeaveRegion() was called inside the function without calling OS_EnterRegion() bfore.
    In debug builds of embOS, the error handler OS_Error() was called with error 151 (OS_ERR_LEAVEREGION_BEFORE_ENTERREGION).
    In release builds the system was blocked because the underflow of region count inhibts all further task switches, or system crashes, because incrementing the region count the next time allows task switches instead of blocking them. The problem existed in all previous versions and is fixed with version 3.32l.
  2. Round-robin task switching corrected.
    Round robin task switching did not work correctly in previous version. A task which was blocked for some reason could be activated. The system crashed during task switch.
    The problem existed since version 3.32j and is fixed with version 3.32l.

Version 3.32k

  1. Handler function _OS_OnTx() for serial communication to embOSView corrected.
    The transmission handler for communication with embOSView might have sent incorrect data to embOSView, because internal control state was updated after sending the data.
    The problem occurred on a new embOS port for a specific CPU only and is fixed with version 3.32k.

Version 3.32h

  1. OS_Error() was required in release build when resource semaphores were used.
    When using release build libraries and resource semaphores, the embOS error handler OS_Error() was required and the file OS_Error.c had to be compiled and linked in a project.
    The problem existed since version 3.28i of embOS and is fixed with version 3.32h.

Version 3.32e

  1. OS_GetMessageCnt() corrected.
    The type of the retun value of OS_GetMessageCnt() was an unsigned integer in release builds, but an integer in debubg builds.
    This was corrected to return an unsigned integer in all builds.
    The problem existed in all previous versions of embOS end is fixed with version 3.32e.

Version 3.32a

  1. embOSView corrected.
    embOSView sometimes showed wrong task state "Terminated" for tasks which were not terminated.
    This bug existed in all previous versions of emBOSView and is fixed with version 3.32a.

Version 3.30d

  1. OS_MEMF_Create() corrected.
    Alignment check of buffers for fixed size memory blocks did not work correctly in debug libraries of embOS.
    OS_Error() was called during OS_MEMF_Create(), even though the memory pool buffers start address was correctly aligned.
    This problem existed since embOS version 3.28m in all debug build libraries and is fixed with version 3.30d.

Version 3.30b

  1. OS_Suspend() corrected.
    OS_Suspend() did not work correctly, when an activated task with higher priority than the running task was suspended.
    When the task with highest priority was suspended during system initialization before embOS was started, embOS crashed during the call of OS_Start(), or called the embOS error handler OS_Error() with error code OS_ERR_INV_TASK (128).
    The same crash occurred, when the application was running in a critical region and a task with higher priority was activated, but not started because of the critical region, and was then suspended by a call of OS_Suspend().
    This problem existed in all previous embOS versions and is fixed with version 3.30b.

Version 3.28q

  1. Problem with suspended tasks which were on delay fixed.
    If a task which was on delay was suspended, the delay timer for that task was not handled.
    This might have resulted in additional longer delay when the task was resumed later.
    This problem existed in all previous embOS versions and is fixed with version 3.28q.

Version 3.28p

  1. OS_Suspend() corrected.
    OS_Suspend() did not work correctly, when the current task was suspended from within an interrupt handler, or from a critical region.
    The application crashed, or called the embOS error handler OS_Error() with error code OS_ERR_INV_TASK (128).
    As OS_Suspend() automatically enters a critical region in debug-trace builds, OS_Suspend() also failed, when it was called to suspend the current task in debug-trace builds of embOS.
    This problem existed in all previous embOS versions and is fixed with version 3.28p.
  1. Alignment problems fixed for fixed size memeory blocks
    Some CPUs, mainly the 32bit RISC types, require aligned buffer start addresses for fixed size memory pools.
    The debug version of embOS now checks alignment of buffer start address and data blocks in the buffer. If data blocks and biffer start address is not aligned, an error is generated and embOS error handler is called during creation of a fixed size memory pool.
    This problem existed in all previous embOS versions and is fixed with version 3.28m.

Version 3.28l

  1. OS_MEMF_Free() added
    The function OS_MEMF_Free() was not included in embOS libraries, but was documented in embOS users manual and was also declared in RTOS.h.
    This problem existed in all previous embOS versions and is fixed with version 3.28l.

Version 3.28k

  1. OS_MEMF_IsInPool() corrected
    OS_MEMF_IsInPool() failed, if a pointer was checked which pointed to the first address after the memory pool. This pointer was reparted as belonging to the pool.
    This problem existed in all previous embOS versions and is fixed with version 3.28g.

Version 3.28g

  1. OS_WakeTask() for trace build corrected
    OS_WakeTask() in trace build disabled task switches.
    This problem existed since version 3.24 and is fixed with version 3.28g.
  2. OS_WaitCSemaTimed() corrected
    Semaphore handling was changed with embOS sources version 3.26.
    Unfortunately,during call of OS_WaitCSemaTimed() an internal control counter was decremented twice, which resulted in wrong control state of semaphore. Overflow of this counter caused, that the calling task remained suspended until the timeout expired, even though, the semaphore was signaled.
    This problem existed in version 3.26 only and is fixed with version 3.28g.
  3. OS_GetMailTimed() / mailbox handling corrected
    During call of OS_GetMailTimed, interrupts were re-enabled too early. If a mail was just put into a mailbox and the timeout occurred at the same time, a mailbox internal control variables which managed waiting tasks was set to a wrong value.
    This resulted in wrong mailbox handling and caused task waiting for mail kept suspended, even though, mail was available. This problem existed in all previous versions of embOS and is fixed with version 3.28g.

Version 3.26a

  1. OS_MEMF_Release() corrected
    OS_MEMF_Release() might have failed according to absolute address of memory block.
    The problem occurred because address calculation was done with 16bit interger value.
    Calculation was modified to use 32bit values to fix the problem.

Version 3.20c

  1. OS_GetMailTimed() corrected
    OS_GetMailTimed() did not retrieve a mail after 256 calls, the waiting task remained suspended. Corrected with version 3.20c of embOS.
    This problem exists in all previous embOS versions and is fixed with version 3.20c.

Version 3.10q

  1. OS_GetMail
    OS_GetMail functions corrected (interrupts disabled before call of _GetMail).
  2. OS_Terminate problem with RR
    OS_Terminate problem with RR tasks corrected. TimerTick could set RR/PP pending between UNMARKTASK and OS_Switch. OS_Switch will then call OS_DoRR, which could append OS_pCurrentTask (the one you want to terminate if e.g. OS_Terminate(NULL)).

Version 3.10m

  1. Sample interrupt handler
    For embOS it is not legal to call OS_EnterInterrupt again after final OS_LeaveInterrupt has been already called. In the sample OS_irq_handler shipped with embOS, there was a possible call of OS_EnterInterrupt after OS_LeaveInterrupt. The sample OS_irq_handler implementation has been corrected.

Version 3.06f

    1st version for ARM using ARM Tools

Known problems

Version 3.20f


Release history

Version Release date Short explanation
V3.40c1 29. May 2009 Additional target CPUs supported
V3.40c 22. Jun 2007 Update to embOS version 3.40c
V3.32 18. Jul 2006 Event objects implemented
V3.30b 24. May 2006 New embOS sources 3.30b
V3.28i 26. Sep 2005 New embOS sources 3.28i with additional error check and new function OS_DeleteRSema()
V3.28g 07. Jul 2005 Official release with new embOS sources 3.28
V3.28 - 3.28f Internal versions, not distributed
V3.26 16. Feb 2005 New embOS libraries V3.26
V3.20f 01. Jun 2004 New embOS libraries V3.20
V3.10l 12. Feb 2003 1st version for ARM using ADS


This document was first released with version 3.06f of the software.
Software released earlier is documented internally.
This information is available at request.

Copyright 2004-2009 SEGGER Microcontroller GmbH & Co.KG. All rights reserved.
For more information, please visit our website or contact us at