Random number generator hanging on TRNG_EV_VALRDY

[Prasad]

Here is my function to generate random numbers of desired length.

#define TRNG_BASE 0x4000D000
#define TRNG_TASKS_START (*(volatile uint32_t *)(TRNG_BASE + 0x000))
#define TRNG_TASKS_STOP  (*(volatile uint32_t *)(TRNG_BASE + 0x004))
#define TRNG_EV_VALRDY   (*(volatile uint32_t *)(TRNG_BASE + 0x100))
#define TRNG_VALUE       (*(volatile uint32_t *)(TRNG_BASE + 0x508))

void sys_random(uint8_t *buf, int len)
{
    volatile uint8_t val;
    volatile int i = 0;
    /* Clear VALRDY */
    TRNG_EV_VALRDY = 0;
    /* Start TRNG */
    TRNG_TASKS_START = 1;
    for (i = 0; i < len; i++)
    {
        printf("Generating random #%d\r\n", i);
        
        /* Wait until value ready */
        while (TRNG_EV_VALRDY == 0);
    
        TRNG_EV_VALRDY = 0;
        buf[i] = (uint8_t)(TRNG_VALUE & 0x000000FF);
    }
    TRNG_TASKS_STOP |= 1;
}

After generating a few(5 to 6) random numbers the function hangs at 

while (TRNG_EV_VALRDY == 0)

.

I am using RIOT OS on nrf52832. What could be the issue here?

[Turbo J]

The RNG is a restricted peripherial when using softdevice. Direcly accessing registers will only work when softdevice is completely disabled.

[Prasad]

There is no softdevice. I am using RIOT OS.