CCS/AM3358: Semaphore creation

Anping Chen

Expert 2900 points

Part Number: AM3358
Other Parts Discussed in Thread: SYSBIOS

Tool/software: Code Composer Studio

There are at least two way to create semaphore

/* Create call back semaphore */

SPI_osalSemParamsInit(&cbSemParams);

cbSemParams.mode = SemaphoreP_Mode_BINARY;

SemaphoreP_Handle cbSem = SPI_osalCreateBlockingLock(0, &cbSemParams);

and

Semaphore_Handle sem_id;

Semaphore_Params params;

int16_t count = (state == Sem_State_Full) ? 1 : 0;

Semaphore_Params_init(&params);

if(order == Sem_Order_Fifo)

{

params.mode = ti_sysbios_knl_Semaphore_Mode_BINARY;

}

else

{

params.mode = ti_sysbios_knl_Semaphore_Mode_BINARY_PRIORITY;

}

Sem_Id_Type sem_id = Semaphore_create(count, &params, &eb);

What is their difference? Thanks

over 5 years ago

0 Rahul Prabhu over 5 years ago

TI__Guru** 116170 points

Anping,

The details of Semaphore modes are documented in the TI RTOS documentation for SYSBIOS modules here:

http://dev.ti.com/tirex/content/tirtos_tivac_2_16_00_08/products/bios_6_45_01_29/docs/cdoc/ti/sysbios/knl/Semaphore.html#.Mode

Please review the description and let us know if you have further questions.

Regards,

Rahul

0 Anping Chen over 5 years ago in reply to Rahul Prabhu

Expert 2900 points

Hi Rahul

Please tell me a little bit why there are two ways, not one, to create semaphore! Thanks

0 Rahul Prabhu over 5 years ago in reply to Anping Chen

TI__Guru** 116170 points

The different semphore behavior determines the way the scheduler handles Tasks pending on the semaphore.

The gist is that FIFO maintains the order of the pend calls. Consider the case where a semaphore is not available and task 1 (with priority 1) calls Semaphore_pend and then Task 2 (with priority 2...higher) calls Semaphore_pend. In the FIFO case, when the semaphore comes available, Task 1 would get it (since it called pend first). In the PRIORITY case, Task 2 would get in (since it has the higher priority).

If you need more details, check out section 4.1 for Semaphore mode details:

http://www.ti.com/lit/ug/spruex3u/spruex3u.pdf

Hope this clarifies the implementation.

Regards,

Rahul

0 Anping Chen over 5 years ago in reply to Rahul Prabhu

Expert 2900 points

Hi Rahul

Thank you for your reply. But I’m a little confused as to

SemaphoreP_Handle SemaphoreP_create(uint32_t count, SemaphoreP_Params *params);

and

ti_sysbios_knl_Semaphore_create: sem_id = Semaphore_create(count, &params, &eb);

can I use Semaphore_create instead of SemaphoreP_create? In other word I like to use one kind of Semaphore functions. Thanks

0 Anping Chen over 5 years ago in reply to Anping Chen

Expert 2900 points

Hi Rahul

Can I use ti_sysbios_knl_Semaphore_create to replace SemaphoreP_create? I like to use one kind of Semaphore functions in my application. Thanks

0 Rahul Prabhu over 5 years ago in reply to Anping Chen

TI__Guru** 116170 points

The two APIs are one and the same. The RTSC tools maps the application level API to the BIOS internal API defines using function macros that will map to the same code during compilation. SemaphoreP_create is the application level API and ti_sysbios_knl_Semaphore_create is the BIOS internal function name that it maps to. Our recommendation is to use the API guide and use the application level APIs rather than using BIOS internal API names.

Regards,

Rahul

Processors

Processors forum

CCS/AM3358: Semaphore creation