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Tx_Thread_Creation application description

This application provides an example of Azure RTOS ThreadX stack usage, it shows how to develop an application using the ThreadX thread management APIs. It demonstrates how to create and destroy multiple threads using Azure RTOS ThreadX APIs. In addition, it shows how to use preemption threshold between threads and change priorities on-fly. The main entry function tx_application_define() is then called by ThreadX during kernel start, at this stage, the application creates 3 threads with different priorities :

  • MainThread (Prio : 5; Preemption Threshold : 5)
  • ThreadOne (Prio : 10; Preemption Threshold : 9)
  • ThreadTwo (Prio : 10; Preemption Threshold : 10)

Once started, the MainThread is suspended waiting for the event flag. The ThreadOne starts to toggle the LED_GREEN each 500ms and ThreadTwo cannot as its priority is less than the ThreadOne threshold. After 5 seconds it sends an event THREAD_ONE_EVT to the MainThread.

After receiving the THREAD_ONE_EVT, the MainThread change the ThreadTwo priority to 8 and its preemption threshold to 8 to be more than the ThreadOne threshold then waits for an event.

Now, the ThreadTwo can preempt the ThreadOne and start toggling the LED_GREEN each 200ms for 5 seconds. Once done it send the THREAD_TWO_EVT to MainThread. Once ThreadTwo_Evt is received, the MainThread resets the ThreadTwo priority and preemption threshold to their original values (10, 10), ThreadOne is rescheduled and the above scenario is redone. After repeating the sequence above 3 times, the MainThread should destroy ThreadOne and ThreadTwo and toggles the LED_GREEN each 1 second for ever.

Expected success behavior

  • LED_GREEN toggles every 500ms for 5 seconds
  • LED_GREEN toggles every 200ms for 5 seconds
  • Success status (After 3 times) : 'LED_GREEN' toggles every 1 second for ever.

Error behaviors

LED_RED toggles every 1 second if any error occurs. an error message is printed to the serial port.

Assumptions if any

None

Known limitations

None

ThreadX usage hints

  • ThreadX uses the Systick as time base, thus it is mandatory that the HAL uses a separate time base through the TIM IPs.

  • ThreadX is configured with 100 ticks/sec by default, this should be taken into account when using delays or timeouts at application. It is always possible to reconfigure it in the "tx_user.h", the "TX_TIMER_TICKS_PER_SECOND" define,but this should be reflected in "tx_initialize_low_level.S" file too.

  • ThreadX is disabling all interrupts during kernel start-up to avoid any unexpected behavior, therefore all system related calls (HAL, BSP) should be done either at the beginning of the application or inside the thread entry functions.

  • ThreadX offers the "tx_application_define()" function, that is automatically called by the tx_kernel_enter() API. It is highly recommended to use it to create all applications ThreadX related resources (threads, semaphores, memory pools...) but it should not in any way contain a system API call (HAL or BSP).

  • Using dynamic memory allocation requires to apply some changes to the linker file. ThreadX needs to pass a pointer to the first free memory location in RAM to the tx_application_define() function, using the "first_unused_memory" argument. This require changes in the linker files to expose this memory location.

    • For EWARM add the following section into the .icf file:
    place in RAM_region    { last section FREE_MEM };
    • For MDK-ARM:
    either define the RW_IRAM1 region in the ".sct" file
or modify the line below in "tx_initialize_low_level.S to match the memory region being used
    LDR r1, =|Image$$RW_IRAM1$$ZI$$Limit|
    • For STM32CubeIDE add the following section into the .ld file:
    ._threadx_heap :
  {
     . = ALIGN(8);
     __RAM_segment_used_end__ = .;
     . = . + 64K;
     . = ALIGN(8);
   } >RAM_D1 AT> RAM_D1

    The simplest way to provide memory for ThreadX is to define a new section, see ._threadx_heap above.
In the example above the ThreadX heap size is set to 64KBytes.
The ._threadx_heap must be located between the .bss and the ._user_heap_stack sections in the linker script.
Caution: Make sure that ThreadX does not need more than the provided heap memory (64KBytes in this example).
Read more in STM32CubeIDE User Guide, chapter: "Linker script".
    • The "tx_initialize_low_level.S" should be also modified to enable the "USE_DYNAMIC_MEMORY_ALLOCATION" flag.

Keywords

RTOS, ThreadX, Threading, Event flags, Preemption threshold

Hardware and Software environment

  • This example runs on STM32WBxx devices

  • This example has been tested with STMicroelectronics P-NUCLEO-WB55.Nucleo boards Revision MB1355C-01 and can be easily tailored to any other supported device and development board.

  • This application uses USART1 to display logs, the hyperterminal configuration is as follows:

    • BaudRate = 115200 baud
    • Word Length = 8 Bits
    • Stop Bit = 1
    • Parity = None
    • Flow control = None

How to use it ?

In order to make the program work, you must do the following :

  • Open your preferred toolchain
  • Rebuild all files and load your image into target memory
  • Run the application