/* 
 * (c) danielinux 2019
 * GPLv.2
 *
 * See LICENSE for details
 */
#include "system.h"
#include <stdint.h>

uint32_t random_uint32(void)
{
    int i;
    uint32_t rand;
    /* enable RNG peripheral clock */
    AHB2_CLOCK_ER |= RNG_AHB2_CLOCK_ER;
    /* enable RNG interrupt, set IE bit in RNG->CR register */
    RNG_CR |= RNG_CR_IE;

    /* enable RNG, set RNGEN bit in RNG->CR. Activates RNG,
     * RNG_LFSR, and error detector */
    RNG_CR |= RNG_CR_RNGEN;

    /* verify no errors, make sure SEIS and CEIS bits are 0
     * in RNG->SR register */
    if (RNG_SR & (RNG_SR_SECS | RNG_SR_CECS))
        return 0;

    /* wait until RNG number is ready */
    while ((RNG_SR & RNG_SR_DRDY) == 0) 
        ;
    /* get value */
    rand = RNG_DR;
    return rand;
}