Tx_CMSIS_Wrapper Application Description
This application provides an example of CMSIS RTOS adaptation layer
for Azure RTOS ThreadX, it shows how to develop an application using the
CMSIS RTOS 2 APIs. It demonstrates how to create multiple threads using
CMSIS RTOS 2 for ThreadX APIs. At the main function, the application
creates 2 threads with the same priority which execute in a periodic
cycle of 7 seconds :
- ‘ThreadOne’ (Priority : osPriorityNormal)
- ‘ThreadTwo’ (Priority : osPriorityNormal)
The function “Led_Toggle()” is the entry function for both threads to
toggle the leds.Therefore it is considered as a “critical section” that
needs protection with a ‘SyncObject’ flag in the file
“app_tx_cmsisrtos.h” Each thread is running in an infinite loop as
following:
- ‘ThreadOne’:
- try to acquire the ‘SyncObject’ immediately.
- On Success toggle the ‘LED_GREEN’ each 500ms for 5 seconds.
- Release the ‘SyncObject’
- Sleep for 10ms.
- repeat the steps above
- ‘ThreadTwo’:
- try to acquire the ‘SyncObject’ immediately.
- On Success toggle the ‘LED_GREEN’ each 200ms for 2 seconds.
- Release the ‘SyncObject’
- Sleep for 10ms.
- Repeat the steps above.
By default the ‘SyncObject’ is defined as “osMutexId_t” .It is
possible to use a semaphore “osSemaphoreId_t” by tuning the compile
flags in the file “app_tx_cmsisrtos.h”.
Expected success behavior
- ‘LED_GREEN’ toggles every 500ms for 5 seconds
- ‘LED_GREEN’ toggles every 200ms for 2 seconds
- Messages on HyperTerminal :
- “** ThreadXXX : waiting for SyncObject !! **” : When thread is
waiting for the SyncObject.
- “** ThreadXXX : waiting SyncObject released **” : When thread put
the SyncObject.
- “** ThreadXXX : waiting SyncObject acquired **” : When thread get
the SyncObject.
Error behaviors
On failure, an error message is printed to the serial port.
Assumptions if any
None
Known limitations
None
Notes
To optimize the application footprint, the following ThreadX
configuration options should be enabled in the tx_user.h file:
#define TX_DISABLE_PREEMPTION_THRESHOLD
#define TX_DISABLE_NOTIFY_CALLBACKS
#define TX_DISABLE_REDUNDANT_CLEARING
#define TX_DISABLE_STACK_FILLING
#define TX_NOT_INTERRUPTABLE
#define TX_TIMER_PROCESS_IN_ISR
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 };
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, CMSIS RTOS, Semaphore, Mutex
Hardware and Software
environment
This application runs on STM32C031C6Tx devices
This application has been tested with STMicroelectronics
STM32C0316-DISCO boards Revision MB1716 A-02 and can be easily tailored
to any other supported device and development board.
A virtual COM port appears in the HyperTerminal:
- Hyperterminal configuration:
- Data Length = 8 Bits
- One Stop Bit
- No parity
- BaudRate = 115200 baud
- 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
- Load images into target memory
- Run the application