H743 FreeRTOS

[HMSEdinburge]

HI I m using H743 Nucleo, to write a RTOS program with 2 tasks which gonna access to the same memory location concurrently.. can anyone advise which  RTOS method to use ? Tasks ? Semaphore? Message Queue? 

[AScha.3]

Hi,

Depends on what you want:

- just use it on both tasks: make a global volatile variable 

- have some control, when a task is allowed to use it: use a semaphore 

 

Don't forget, you are on a single core here, so it's never really concurrent in many tasks, it's always only one task running for some milliseconds, then the other or next.

[HMSEdinburge]

ok agree, not concurrent but simultaneously... in this case, could the 2 tasks access to the same memory location (where ext. input data from ADC are stored)

[AScha.3]

Right, problem solved. 

-> use global volatile variable.

[mƎALLEm]

Hello,

What do you mean by "access to the same memory location concurrently"?

Even with RTOS only one instruction is executed at a time. The RTOS scheduler makes the tasks seem to be executed in parallel.

STM32H743 MCU is a single core product. There is no worry about the HW concurrence to a memory.

Now if you are talking about mutual exclusion on a specific variable, structure etc, this is another thing.. You need to manage it with mutex or semaphore ...

[HMSEdinburge]

How to acheive concurrent if use mutex? doesn't mutex mean exclude 1 task from another?

[mƎALLEm]

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@HMSEdinburge wrote:

How to acheive concurrent if use mutex? doesn't mutex mean exclude 1 task from another?

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If you are not familiar with RTOSes, I suggest you to learn about it.

and especially mutexes: see that video: https://www.youtube.com/watch?app=desktop&v=I55auRpbiTs&t=0s

 

"not concurrent but simultaneously... in this case, could the 2 tasks access to the same memory location"

Nothing is done simultaneously in RTOS. As I said,  with RTOS only one instruction is executed at a time. The RTOS scheduler makes the tasks seem to be executed in parallel.

 

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@HMSEdinburge wrote:

How to acheive concurrent if use mutex? doesn't mutex mean exclude 1 task from another?

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That doesn't have a specific relation with STM32.

[Andrew Neil]

Sounds like what you really need is a tutorial on FreeRTOS (maybe RTOS in general) - none of this is specific to STM32.

https://www.freertos.org/Documentation/01-FreeRTOS-quick-start/01-Beginners-guide/00-Overview

https://www.freertos.org/Documentation/00-Overview 

https://www.freertos.org/Community