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cpu: nrf51822/periph/random Power optimization

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This commit is contained in:
Frank Holtz 2015-05-09 17:33:42 +02:00
parent 2682c38ee8
commit 85248ddec8
1 changed files with 32 additions and 6 deletions
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38
cpu/nrf51822/periph/random.c
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@ -14,6 +14,7 @@
* @brief Driver for the NRF51822 random number generator
*
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
* @author Frank Holtz <frank-riot2015@holtznet.de>
*
* @}
*/
@ -27,31 +28,56 @@
void random_init(void)
{
NRF_RNG->POWER = 1;
NRF_RNG->TASKS_START = 1;
/* The RNG is initiated every time when RNG read is called
* This reduces power consumption when RNG is not needed
*/
}
int random_read(char *buf, unsigned int num)
{
unsigned int count = 0;
/* power on RNG */
NRF_RNG->POWER = 1;
/* Generate events when RNG is finished */
NRF_RNG->INTENSET = RNG_INTENSET_VALRDY_Msk;
/* Start Task */
NRF_RNG->TASKS_START = 1;
/* NRF51 PAN #21 */
NRF_RNG->EVENTS_VALRDY = 0;
while (count < num) {
while (NRF_RNG->EVENTS_VALRDY == 0);
NRF_RNG->EVENTS_VALRDY = 0;
/* sleep until number is generated */
while (NRF_RNG->EVENTS_VALRDY == 0) {
/* enable wake up on events for __WFE CPU sleep */
SCB->SCR |= SCB_SCR_SEVONPEND_Msk;
/* sleep until next event */
__SEV();
__WFE();
__WFE();
}
buf[count++] = (char)NRF_RNG->VALUE;
/* NRF51 PAN #21 */
NRF_RNG->EVENTS_VALRDY = 0;
/* clear interrupt state */
NVIC_ClearPendingIRQ(RNG_IRQn);
}
/* power off RNG */
NRF_RNG->POWER = 0;
return count;
}
void random_poweron(void)
{
NRF_RNG->POWER = 1;
/* RNG is powered on when needed */
}
void random_poweroff(void)
{
NRF_RNG->POWER = 0;
/* RNG is powered off automaticly */
}
#endif /* RANDOM_NUMOF */