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 listens 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 BLUE
LED is toggled once.
Expected success behavior
GREEN_LED toggles every 200ms and BLUE_LED toggles every
500ms indefinitely.
Error behaviors
On failure, an error message is printed to the serial port while the
GREEN_LED and BLUE_LED are turned OFF.
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
#define TX_DISABLE_ERROR_CHECKING
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, by updating the
“TX_TIMER_TICKS_PER_SECOND” define in the “tx_user.h” file. The update
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 requires 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_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, Message Queue, Event chaining
Hardware and Software
environment
- This application runs on STM32C071xx devices
- This application has been tested with STMicroelectronics NUCLEO-C071RB
board MB2046 Rev. B01 and can be easily tailored to any other supported device and
development board.
- This application uses USART2 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