RE: Random number without softdevice

Roger Clark — Fri, 03 Feb 2017 21:40:13 GMT

Thanks for posting. I think that may come in handy, albeit I could just use the driver in my case ;-)

RE: Random number without softdevice

CurtisHx — Fri, 03 Feb 2017 20:25:03 GMT

The RNG is probably one of the most simple peripherals to run on the nRF5s. Here's the way we did it (bare metal) to generate a random number.

From the functional description in the nRF51 Reference Manual

The RNG is started by triggering the START task and stopped by triggering the STOP task. When started, new random numbers are generated continuously and written to the VALUE register when ready. A VALRDY event is generated for every new random number that is written to the VALUE register. This means that after a VALRDY event is generated the CPU has the time until the next VALRDY event to read out the random number from the VALUE register before it is overwritten by a new random number

Basically, start the RNG, wait for the VALRDY, stop the RNG, and read out the random number. It's really, really simple.

uint8_t GenerateRandomNumber()
{
   NRF_RNG_VALRDY = 0;
   NRF_RNG->TASKS_START = 1;
   while(NRF_RNG->VALRDY == 0){}
   NRF_RNG->TASKS_STOP = 1;
   return NRF_RNG->VALUE;
}

RE: Random number without softdevice

Sigurd — Fri, 03 Feb 2017 13:18:56 GMT

Hi,

There is a RNG example in the SDK:

<SDK_InstallFolder>\examples\peripheral\rng

If you dont want to use the SDK RNG driver, you can also find a bare-metal example on how to use the RNG peripheral here.