AVR-Chat

One of the common pseudo-random, non-deterministic schemes is to have  
a free-running timer. You just grab a value when you need a new  
"number". It will be non-deterministic but might not be truly random  
in the statistical sense. It will average to the median.

Jim Wagner
Oregon Research Electronics

On Jan 8, 2011, at 1:39 PM, Chuck Hackett wrote:

> This is mostly a "mind experiment" because I don't have a current  
> need but, is there
> a way to obtain a truly random (8-bit is good enough) number on an  
> AVR? I'm not
> talking "random" in the statistically pure sense, just non- 
> deterministic.
>
> I'm only thinking of using it on startup.
>
> Sampling a "noisy diode" would be great but I want to do it without  
> having to add
> external hardware or dedicate an I/O pin to the effort.
>
> All I can think of is something like setting up one of the analog  
> inputs as 'free
> floating', turning the gain all the way up, and violating all the  
> "how to avoid ADC
> noise" rules and taking a sample.
>
> I don't think the timers would be helpful because these would tend  
> to be
> deterministic and, by nature, run in sync with any code that would  
> be sampling them.
>
> Ideas?
>
>
> 



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