Semaphore implementation for the Radio

[haruthakop]

Dear Nordic developers,

In my project there is a possibility that CPU and RADIO EasyDMA peripheral can access to the same memory RAM locations in parallel. I read from the manual that RADIO EasyDMA unit is accessing to a RAM location between READY and DISABLED radio events.

Is there any mechanism like semaphore hardware unit SPIS to prevent simultaneous access to a specified RAM location. I don't want to copy memory locations, beacause of my timing requirements.

I'd really appreciate any advice.

Best regards, Harut

[Susheel Nuguru]

Sorry, there is no such mechanism for RADIO

[Susheel Nuguru]

I think you can implement your own MUTual EXclusion semaphore and change the micro lib library where RADIO transaction is enabled to fetch this mutex first.

uint32_t mutex_acquire(uint8_t * p_mutex)
{
  bool success;
  int irq_was_masked;
  
  /* Disable Interrupts if not */
  irq_was_masked = __disable_irq(); 

  success = (*p_mutex != MUTEX_TAKEN);
  *p_mutex = MUTEX_TAKEN;
  
  /* Enable Interrupts if disabled by this function */
  if (!irq_was_masked)
  {
    __enable_irq();
  }
  
  if (success)
  {
    return UESB_SUCCESS;
  }
  else
  {
    return UESB_MUTEX_ALREADY_TAKEN_ERROR;
  }  
}

uint32_t mutex_release(uint8_t * p_mutex)
{
  int irq_was_masked;

  /* Disable Interrupts if not */
  irq_was_masked = __disable_irq(); 

  *p_mutex = MUTEX_FREE;

  /* Enable Interrupts if disabled by this function */
  if (!irq_was_masked)
  {
    __enable_irq();
  }
  
  return UESB_SUCCESS;
}

Keep in mind the possibility of a deadlock as mentioned here which you need to handle.