Implementing a mutex

[Bret Foreman]

I need a mutex and I found this information at the ARM site: infocenter.arm.com/.../index.jsp

Is there anything I should be aware of in using this technique to implement a mutex?

[Carles]

Hi there,

Are you using the SoftDevice?

If so, there are already SVCs provided by the SoC framework that implement mutexes and critical regions:

sd_mutex_new sd_mutex_acquire sd_mutex_release

sd_nvic_critical_region_enter sd_nvic_critical_region_exit

Regards,

Carles

[Guilherme de Paula]

I've tried that but when calling "sd_mutex_acquire()" in the handler code it goes into HardFault.

[Ole Morten]

To answer the original question first: I believe that the ARM Cortex M0 does not support the instructions needed to follow that guide in detail, and I would as Carles say therefore recommend you to use the softdevice API functions.

Remember that softdevice functions can only be called from interrupt with priority 3 and the main context, not from interrupts with priority 2. See this answer for more details.

Edit: You can change the priority of interrupts with the sd_nvic_SetPriority() function.

[Ole Morten]

Please see my separate answer, which most likely explains why this happens.