Random outcome on multiple devices

[Art]

It sounds like it would work.
That would be the first thing I'd try now, nice one.
.. and if not, then tapping the centre of a divider (two resistors from +ve to Gnd).
Still cheaper than timing a cap discharge.

I can't say I've tried to make two devices produce a different result,
just one device from one launch to the next.

(Never done this)

What about reading a resistor on analog pin? A high value, maybe 100K, would that produce a reasonably wide range of seeds?

Robert

Edit: since no 2 resistors are exactly alike, the voltage should vary.

[Demon]

Even better, use a LED and 330R resistor. You're bound to get different voltages and it serves as a power indicator.

Robert

[Aussie Barry]

Hi Guys,

All great ideas - thank you.
I have decided to program each PIC separately making subtle differences to LED flash rates and "off-time" periods to give an overall effect of randomness.
This is a one-off project that I am doing as a labour of love for my company. As such, I just want to get in and get out as quickly as possible

Cheers
Barry
VK2XBP

[HenrikOlsson]

Hi,
One possible issue with using the ADC is that the 12F508 being mentioned in the first post doesn't have one....

/Henrik.

[Art]

Still in general, it sounds like something to try.
You get 14 bit ADC with pic if I remember,
should be high enough resolution to vary with resistor tolerance.

I was keen to see how it panned out without doing it myself

[HenrikOlsson]

As long as we stick to 8-bit PICs (which is what PBP supports) there's a quite a selection devices with 12bit ADC and two devices with 16bit ADC (18F8xJ72). All of them are enhanced 16F1xxx or 18F parts though, the smallest I could find thru a quick look is 28pin.

/Henrik.

[Aussie Barry]

Hi All,

So much has happened in the last week or so...
In typical fashion, the customer (my company on this occasion) has requested "additional functions" to be included which are above and beyond the original scope of work. The degree of modification has required a complete re-design.
I won't bore you with the trivial details but the system now requires three separate LED flash sequences AND an auto function to scroll through the three stand-alone sequences.
No - problems, just more time and code...

I have now moved to a PIC16F1503. I would still like to use some sort of random number generation routine to achieve a random display flash rate between the thirty two individual PIC's without having to separately programming them. I could take the easy way out and do it manually but I like the idea of coming up with something eloquent

Here is my thought:
I can use my MeLabs programmer to generate a unique serial number for each PIC that I program. I understand this is a straight forward process. I would like to my program to read this unique serial number and use it as the seed for the random number generation source.

Here is my question:
Can is this concept be taken to a reality or am I barking up the wrong tree?

Comments and suggestions greatly appreciated.

Cheers
Barry
VK2XBP

[Darrel Taylor]

Well, the short answer is YES.

The programmer can auto increment a serial number that gets programmed into Flash Memory.
That value can be read back with READCODE.

[Archangel]

Here is my thought:
I can use my MeLabs programmer to generate a unique serial number for each PIC that I program. I understand this is a straight forward process. I would like to my program to read this unique serial number and use it as the seed for the random number generation source.

I think this would be the same as giving the PIC a fixed seed in the code. You might try a subprogram to save the last number used and then shutting it down. At startup have it read that value from eeprom.