How to initialize random without time

Question

I am programming a microcontroller (PSoC5), which doesn't have a system time.

What is the best way to generate a seed to initialize srand?

TIA

`1` more than used last time? *Everytime you use `srand()` you could read/update a file with the seed.* — pmg, Oct 02 '21 at 12:25

score 6 · Accepted Answer · answered Oct 02 '21 at 12:31

6

If the chip has ADCs, one option is to take advantage of noise picked up on the ADCs. Basically, you can take a few reads of the ADCs, then bitwise AND to keep the least significant bit. Then use the all of the least significant bits sampled to generate your seed.

answered Oct 02 '21 at 12:31

Jonathon S.

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I like the idea, I try it out later and accept your answer – Philip F. Oct 02 '21 at 12:34
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this is how `/dev/random` is implemented. It reads the random input from different sources and combines it. – alinsoar Oct 02 '21 at 13:02
@alinsoar Nice tip. Thanks. – Jonathon S. Oct 02 '21 at 15:19

How to initialize random without time

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