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Smart Bluetooth

Anonymous
Not applicable

Hi all,

I'm using the 20736's random number generator and I seem to be getting some repeated numbers once in a while (but more often than expected).

I'm wondering if it's a pseudo-random number generator (software, needs manual seeding), instead of a hardware one (which does self-seeding).

The problem is really when, for example, I use 1000 different devices to generate their own 32-bit ID numbers.  When the central retrieves their IDs, we noticed that some ID numbers were generated by a few devices.

Example:

Id 0x12345678 only 1 device

...

Id 0x9ABCDEF only 1 device

...

Id 0x34FE0207 was generated by 4 devices

...

Id 0xFF810ADD was generated by 3 devices

...

etc

In the end, the central reported that there only about 700 unique IDs among those 1000 devices.

Is this an expected limitation or am I doing something wrong?

Here's what I did:

UINT32 random_number;

ulp_rand(&random_number, 1);

Thanks!

Gil

Message was edited by: Guilherme de Paula

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1 Solution
Anonymous
Not applicable

Hello Guilherme,

Yes, it is a true HW Random Number generator.

You will need to wait until 500ms after boot in order to use the HW RNG.

Hope this helps.

Thanks

JT

View solution in original post

3 Replies
Anonymous
Not applicable

Hello Guilherme,

Have you seen this post: Re: how to get a random number with the sdk?

Hope this helps

Thanks

JT

Anonymous
Not applicable

Hi JT,

Thanks, I've tried those but it doesn't help.

Do you know if the random number generator is a hardware RNG or software-based?

Thanks,

Gil

0 Likes
Anonymous
Not applicable

Hello Guilherme,

Yes, it is a true HW Random Number generator.

You will need to wait until 500ms after boot in order to use the HW RNG.

Hope this helps.

Thanks

JT

View solution in original post