non-random behaviour

[Alan Ambrose]

Hi,

I'm trying to generate some time variant values for testing purposes... rand() always returns 1447534768! This is in the proximity app FWIW.

So, I thought I would use the hardware RNG, looking at the example rng_example. Now:

NRF_RNG->TASKS_START=1;
...
NRF_RNG->EVENTS_VALRDY=0;
while(NRF_RNG->EVENTS_VALRDY==0) {}

Just waits for ever?

Alan

[Martijn]

NRF_RNG->EVENTS_VALRDY is a hardware event. It Will be set to non zero when the random generator had finished generating a number.

Note that the current version of the hardware has some faults. There will be no new number generated after the first. You meed to stop the generator and restart it again to get a new random number. See the PAN-028 document.

[Stanley Cheng]

Hi,

I can get a random number by using RNG with following code.

// sd_softdevice_enable(NRF_CLOCK_LFCLKSRC_XTAL_20_PPM, softdevice_assertion_handler); for (;;) { NRF_RNG->EVENTS_VALRDY = 0; NRF_RNG->TASKS_START = 1; while(NRF_RNG->EVENTS_VALRDY==0) {} u8_randNum = (u8)NRF_RNG->VALUE; }

However, It seems stuck with NRF_RNG register accessing when sd_softdevice_enable is called in the program beginning.

Thanks for help. Stanley

[Bastiaan]

The softdevice uses the RNG. So when you try to write any register of the RNG when the softdevice is enabled the device wil go into hardfault.

You need to use the functionality provided by the soc libary: https://devzone.nordicsemi.com/documentation/nrf51/4.3.0/html/group__nrf__soc__api.html#ga7e372c86c718f517174c53a611792489

I do not know how these work exaclty, but it is the only way to use the RNG when softdevice is enabled.

[Guest]

The softdevice uses the RNG. So when you try to write any register of the RNG when the softdevice is enabled the device wil go into hardfault.

You need to use the functionality provided by the soc libary: https://devzone.nordicsemi.com/documentation/nrf51/4.3.0/html/group__nrf__soc__api.html#ga7e372c86c718f517174c53a611792489

I do not know how these work exaclty, but it is the only way to use the RNG when softdevice is enabled.

[Bastiaan]

Thanks