any limitation to call nrf_drv_rng_rand?

Question

I am developing SDK17.0.0 based application with S112.

when I try getting a random value at the end of main, the nrf_drv_rng_rand return err_code=0x05, and it leads to "<error> app: Fatal error and <warning> app: System reset".

When I use button to trigger nrf_drv_rng_rand call, it works well.

Is it known issue? How can I workaround it?

Thanks,

srony

Einar Thorsrud · Accepted Answer

Hi Srony, 
 srony said: My function calls to nrf_drv_rng_rand with length=2, is it possible because of too long to generate in time? 
 It could have been, if the driver was initialized immediately before this call, but It seems there is another problem here. 
 srony said: So I want to confirm if it's essential to run nrf_drv_rng_init before using nrf_drv_rng_rand? 
 Yes, that is necessary. The RNG driver has an assert for that, but the assert is only used for debug builds, which is probably why you have not noticed before. It cannot work without calling nrf_drv_rng_init() first, before any other calls to nrf_drv_rng_*

any limitation to call nrf_drv_rng_rand?

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