POSIX support in FreeRTOS on STM32

[selracelosuarg]

Hello,
As far as I know,
STM32 does not support the POSIX abstraction layer for FreeRTOS.

That means I can not use functions like:

• Interact with tasks through: 'pthread_create', 'pthread_join'..
• Use POSIX glue elements like: 'pthread_mutex'...
• Etc

If I am porting a big FreeRTOS project that is using POSIX to STM32:  what I need to do? Is there a way of achieving it painlessly?

Thanks,

Carles

[mƎALLEm · Accepted solution]

Hello,

I don't think POSIX-FreeRTOS is supported natively by STM32 but I think you need to do it yourself. See https://www.freertos.org/Documentation/03-Libraries/05-FreeRTOS-labs/03-FreeRTOS-plus-POSIX/00-FreeRTOS-Plus-POSIX

https://github.com/FreeRTOS/Lab-Project-FreeRTOS-POSIX

[selracelosuarg]

Thanls @mƎALLEm ,

I will try to use this FreeRTOS Lab Project and will see if it works (and then I will set it as 'Accept as Solution'.

Many thanks!

[selracelosuarg]

I am trying to compile that 'Lab-Project-FreeRTOS-POSIX' inside my project but I am having some troubles in some "redefinitions" of types or something related wit that.

If I add the required 'include paths' to the build system, I got following errors:

Core/Src/sysmem.c:30:35: error: 'NULL' undeclared here (not in a function)
   30 | static uint8_t *__sbrk_heap_end = NULL;

Core/Src/sysmem.c:53:13: error: unknown type name 'ptrdiff_t'
   53 | void *_sbrk(ptrdiff_t incr)

So I will keep trying it, but it seems it is not just "plug & play"

Thanks,
Carles

[mƎALLEm]

Hello,

ST is not the provider of that software, so please contact the developers of that POSIX wrapper.

Thanks.

[selracelosuarg]

Ok. Then from 'STM32' part the current answer is that is not possible to use 'POSIX' in STM32 platform, is that correct?
Thanks,
Carles

[Andrew Neil]

---

@selracelosuarg wrote:

is not possible to use 'POSIX' in STM32 platform, is that correct?

---

No.

It's just that ST does not provide it as a "ready-to-go" example.

FreeRTOS is an independent 3rd-party product: https://www.freertos.org/ 

The FreeRTOS site says:

NOTE: FreeRTOS-Plus-POSIX is a FreeRTOS Labs project provided in the hope that it is useful. It is not a complete pthreads implementation, and does not necessary meet our production code quality standard. FreeRTOS-Plus-POSIX is provided in the Lab-Project-FreeRTOS-POSIX

https://www.freertos.org/Documentation/03-Libraries/05-FreeRTOS-labs/03-FreeRTOS-plus-POSIX/00-FreeRTOS-Plus-POSIX 

FreeRTOS Forums: https://forums.freertos.org/ 

[selracelosuarg]

Thanks, I understand.
My point is:
"ST does not provide native support for POSIX out of the box, unlike its support for CMSIS_v2, for example."

Other frameworks, such as esp-idf, offer POSIX support by default, which is why I raised the question. I wanted to check if there is a "native" way to achieve this using STM32 tools or not.

So far, I have managed to compile and run a project using POSIX.

Below is the CMakeLists.txt code I needed to add to make it work:

{
[...]

# Create the 'CMake' configuration for 'Lab-Project-FreeRTOS-POSIX'
add_library(freertos_posix STATIC)

file(GLOB_RECURSE FREERTOS_POSIX_C_FILES "libs/Lab-Project-FreeRTOS-POSIX/*.c")
target_sources(freertos_posix PRIVATE
    ${FREERTOS_POSIX_C_FILES}
)

target_include_directories(freertos_posix
    PRIVATE
    # 'Parent' include paths required by 'freertos_posix'
    Core/Inc
    Middlewares/Third_Party/FreeRTOS/Source/include
    Middlewares/Third_Party/FreeRTOS/Source/portable/GCC/ARM_CM4F
    # Library itself include paths
    libs/Lab-Project-FreeRTOS-POSIX/FreeRTOS-Plus-POSIX/include/portable/
    libs/Lab-Project-FreeRTOS-POSIX/FreeRTOS-Plus-POSIX/include/portable/st/stm32l475_discovery # TODO: create the corresponding for my board

    # Following are also required not just for the library, but also for the project, so set them as PUBLIC
    PUBLIC
    libs/Lab-Project-FreeRTOS-POSIX/include/
    libs/Lab-Project-FreeRTOS-POSIX/FreeRTOS-Plus-POSIX/include
    libs/Lab-Project-FreeRTOS-POSIX/include/private # TODO: check why it must be public
)

# Add linked libraries
target_link_libraries(${CMAKE_PROJECT_NAME}
    stm32cubemx

    # Add user defined libraries
    freertos_posix
)

Thanks!
Carles

[Andrew Neil]

---

@selracelosuarg wrote:

"ST does not provide native support for POSIX ...

---

It's not so much about ST providing it, as the RTOS providing it.

Eclipse ThreadX (formerly Azure RTOS) has an Adaptation layer for POSIX:

https://github.com/eclipse-threadx/threadx#:~:text=RTOS%20APIs%20(FreeRTOS%2C-,POSIX,-%2C%20OSEK%2C%20etc.).

https://github.com/eclipse-threadx/threadx/tree/master/utility/rtos_compatibility_layers/posix 

[selracelosuarg]

Sorry @Andrew Neil , but I don't agree with you, I see your point, but I don't share it.

See for example:

https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-reference/system/pthread.html

But as far, I think it is clear for me. STM32 is not giving to me a similar think as 'ESP-IDF' does, so it is on my own (or as you are saying, the RTOS provider itself responsability). That is all I wanted to know.

Thanks,

Carles