Random outcome on multiple devices

[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.

[Darrel Taylor]

I think this would be the same as giving the PIC a fixed seed in the code.

Exactly!
Using the U2's incrementing serial number ... Each PIC has a "Fixed Seed".
But each of the 32 PICs are guaranteed to have a different seed, therefore a different blink pattern on power-up.

They are all running the same sequence of 65535 pseudo random numbers, but they all start at a different point in that sequence.

[Aussie Barry]

Thanks for the sanity check guys
Glad to know I am on the right track.

I should be able to sort out the serial number start and incremental values but I am curious to know the best place to store the information in flash memory.
I will be totally honest - I am now working well beyond the limits of my knowledge base. A simple recommendation would be appreciated. A recommendation along with an explanation as to why would superb. I revel in every opportunity to learn something along the way.

Please note: I have RTFM. Reading is one thing, comprehending is something altogether different.

Cheers
Barry
VK2XBP

[Darrel Taylor]

I would suggest putting it at the end of Program Memory.

The 1503 has 2K words of flash, so two locations starting at 07FEh.
It will store the lowbyte and highbyte separately.

Temp   VAR WORD
Seed   VAR WORD

READCODE $7FE, Temp
Seed.LowByte = Temp.LowByte
READCODE $7FF, Temp
Seed.HighByte = Temp.LowByte

I don't have access to a 1503 today, but I think it should work.

[Aussie Barry]

Legendary response Darrel - thank you!

I will keep you posted with project milestones as they are reached.

Cheers
Barry
VK2XBP