RNG interrupt handler not called

RE: RNG interrupt handler not called

akofoed — Sun, 16 May 2021 15:24:59 GMT

Thank you very much - it worked.

I must have slept during C-class when volatile was the subject.

RE: RNG interrupt handler not called

Dmitry — Sun, 16 May 2021 14:32:26 GMT

Hi,

the compiler optimizes (throws away) your busy-wait loop because it has no idea that random_number_index may change outside of this loop. Try to define random_number_index as volatile.

RE: RNG interrupt handler not called

akofoed — Sun, 16 May 2021 10:35:00 GMT

Hi,

I seem to have a similar issue with the RNG. I am not using the SoftDevice but it seems that the RNG does not run the interrupt function no matter what priotity I give it.

The issue is when waiting for the RNG to generate the correct number of numbers.

Using while(random_number_index < len) {}; does not work, while nrf_delay_ms(1); does!

NRFX:

static int random_number_index;
static uint8_t *random_number_buf_ptr;
static int random_number_max_len;

void rng_event_handler(uint8_t rng_data)
{
    if (random_number_index < random_number_max_len)
    {
        random_number_buf_ptr[random_number_index] = rng_data;
        random_number_index++;
    }
}

int mcu_rng_generate(int len, uint8_t *rng_buf)
{
    // Reset random number counter
    random_number_index = 0;

    // Setup safety so that RNG does not fill up buffer beyound len
    random_number_max_len = len;
    random_number_buf_ptr = rng_buf;

    // Start random number generator
    nrfx_rng_start();

    // Wait for required number of random numbers to be generated
    // nrf_delay_ms(1); // <-- THIS WORKS
    while(random_number_index < len) {}; // <-- THIS DOES NOT WORK
    // NRF_LOG_INFO("%d < %d", random_number_index, len);

    // Stop random number generator
    nrfx_rng_stop();

    return NRF_SUCCESS;
}

// Random number generator
int mcu_rng_init()
{
    // Initialise random number generator
    nrfx_rng_config_t config = NRFX_RNG_DEFAULT_CONFIG;
    return nrfx_rng_init(&config, rng_event_handler);
}

Same thing when using the HW registers directly:

int mcu_rng_generate(int len, uint8_t *rng_buf)
{
    // Reset random number counter
    random_number_index = 0;

    // Setup safety so that RNG does not fill up buffer beyound len
    random_number_max_len = len;
    random_number_buf_ptr = rng_buf;

    /* Configure for bias correction. */
    NRF_RNG->CONFIG = RNG_CONFIG_DERCEN_Enabled << RNG_CONFIG_DERCEN_Pos;

    /* Enable value ready interrupt. */
    NRFX_IRQ_PRIORITY_SET(RNG_IRQn, 6);
    NRFX_IRQ_ENABLE(RNG_IRQn);

    NRF_RNG->INTENSET = RNG_INTENSET_VALRDY_Enabled << RNG_INTENSET_VALRDY_Pos;

    /* Start random number generation. */
    NRF_RNG->TASKS_START = 1U;

    /* Wait for required number of random numbers to be generated. */
    // nrf_delay_ms(1); // <-- THIS WORKS
    while(random_number_index < len); <-- THIS DOES NOT WORK!

    /* Stop random number generator. */
    NRF_RNG->TASKS_STOP = 1U;

    return NRF_SUCCESS;
}


void RNG_IRQHandler(void)
{
    // Clear event
    NRF_RNG->EVENTS_VALRDY = 0U;
    if (random_number_index < random_number_max_len)
    {
        random_number_buf_ptr[random_number_index] = NRF_RNG->VALUE;
        random_number_index++;
    }
}

I have tried setting the NRFX_IRQ_PRIORITY_SET(RNG_IRQn, 6); to different things (0 and 12) but no difference.

Can anybody help explaining what nrf_delay_ms(1); does differently than the busy-waiting version?

Kind regards

RE: RNG interrupt handler not called

David Anthony — Thu, 23 May 2019 14:58:10 GMT

In the end, as this is a relatively simple peripheral, I decided to access the hardware directly. Works fine.

void generateRandomNumbers(uint8_t * p_random_numbers)
{
   assert(p_random_numbers != NULL);

   random_number_pointer = p_random_numbers;

   /* Reset random number counter. */
   random_number_index = 0U;

   /* Initialise random number generator. */

   /* Configure for bias correction. */
   NRF_RNG->CONFIG = RNG_CONFIG_DERCEN_Enabled << RNG_CONFIG_DERCEN_Pos;

   /* Enable value ready interrupt. */
   sd_nvic_EnableIRQ(RNG_IRQn);

   NRF_RNG->INTENSET = RNG_INTENSET_VALRDY_Enabled << RNG_INTENSET_VALRDY_Pos;

   /* Start random number generation. */
   NRF_RNG->TASKS_START = 1U;

   /* Wait for required number of random numbers to be generated. */
   while(random_number_index < CHALLENGE_LEN);

   /* Stop random number generator. */
   NRF_RNG->TASKS_STOP = 1U;
}


void RNG_IRQHandler(void)
{
   /* Random value ready. */

   /* Clear event. */
   NRF_RNG->EVENTS_VALRDY = 0U;

   random_number_pointer[random_number_index] = NRF_RNG->VALUE;

   /* Move on to next location. */
   random_number_index++;
}

RE: RNG interrupt handler not called

David Anthony — Mon, 20 May 2019 14:39:57 GMT

Thanks. OK will look at that.

RE: RNG interrupt handler not called

Kenneth — Mon, 20 May 2019 11:46:42 GMT

Hello,

I assume \nRF5_SDK_15.3.0_59ac345\examples\peripheral\rng\ can be used as reference, just make sure that you define SOFTDEVICE_PRESENT if used with the softdevice.

Best regards,
Kenneth