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Tx_Thread_MsgQueue application description

This application provides an example of Azure RTOS ThreadX stack usage, it shows how to develop an application using the ThreadX message queue APIs. It demonstrates how to send and receive messages between threads using ThreadX message queue APIs. In addition, it shows how to use the event chaining feature. 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 and 2 message queues :

  • MsgSenderThreadOne (Priority : 5; Preemption Threshold : 5)
  • MsgSenderThreadTwo (Priority : 5; Preemption Threshold : 5)
  • MsgReceiverThread (Priority : 10; Preemption Threshold : 10)
  • MsgQueueOne (shared by MsgSenderThreadOne and MsgReceiverThread)
  • MsgQueueTwo (shared by MsgSenderThreadTwo and MsgReceiverThread)

MsgSenderThreadOne puts the message TOGGLE_LED on MsgQueueOne each 200 ms. MsgSenderThreadTwo puts the message TOGGLE_LED on MsgQueueTwo each 500 ms. MsgReceiverThread listen on both message queues :

  • When a message is available on MsgQueueOne, the GREEN LED is Toggled once.
  • When a message is available on MsgQueueTwo, the RED LED is Toggled once.

Expected success behavior

GREEN_LED toggles every 200ms and RED_LED toggles every 500ms if the application is running successfully.

Error behaviors

LED_RED toggles every 1 second if any error occurs.

Assumptions if any

None

Known limitations

None

Notes

  1. Some code parts can be executed in the CCM-RAM (64 KB) which decreases critical task execution time, compared to code execution from Flash memory. This feature can be activated using '#pragma location = ".itcmram"' to be placed above function declaration, or using the toolchain GUI (file options) to execute a whole source file in the CCM-RAM.

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_low_level_initilize.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, Message Queue, Event chaining

Hardware and Software environment

  • This application runs on STM32F429xx devices
  • This application has been tested with STMicroelectronics STM32F429ZI Nucleo boards Revision MB1137 B-01 and can be easily tailored to any other supported device and development board.

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