Andrew G Williams wrote:
>
> I'll shortly need to use a 16F84 to generate a series of random pulses (truly
> random, not generated by a pseudo-random algorithm). Does anyone know a
> straightforward way of doing this?
The difference between 'truly random' and PR becomes trivial if you use
the
correct PRN generator. If you use, for instance the GPS p-code PRN
generator,
you will only get the same pattern after two-hundrend-and-something days
(clocked
at 10Mb/s)

> I suppose the usual approach is to pass a low current through a diode,
> amplify the noisy output and then produce pulses from a comparator (but
> please correct me if that's wrong). I was wondering if the PIC itself
> contains any inherent noisy or random signals, or can be persuaded to. If so,
> genuine random pulses could perhaps be generated without any extra
> components.
The PIC does have a randomizing function - just set BRGH=1 and receive a
few
bytes on the USART :))

> Then again, I could use one with a built-in ADC or comparator. If I did that,
> would the noisy signal need amplifying before being input to the PIC? I can't
> find anything in the application notes about these things, so any advice
> would be appreciated.
Go PRN. I've done a few correlation tests with PRN codes and they
generally never
cross-correlate. Of course, some smarty-pants will now start a thread on
noise
theory that will take years off my <delete> button...

--
Friendly Regards

Tjaart van der Walt
mailto:tjaart@wasp.co.za
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