RANDOM and 12F683 - generates same values each time

[CuriousOne]

Hello.

On power up, I need to get some random numbers.

I'm using the code below:

RANDOM DROEBITI
PIRVELI=(DROEBITI//6)+1
RANDOM DROEBITI
MEORE=(DROEBITI//6)+1
RANDOM DROEBITI
MESAME=(DROEBITI//6)+1
RANDOM DROEBITI
MEOTXE=(DROEBITI//6)+1

I always get same results:

8
7
2
4

Why?

[HenrikOlsson]

Hi,
Because that's how RANDOM works.... From the manual

RANDOM is not a true random-number generator. It performs a complex math operation on the seed value, resulting in "seemingly random" result. The same seed value will always yield exactly the same result.

There are a couple of ways to get a better "randomness". For example, use the ADC and sample a something noisy, use that value as the seed.

ADCIN 1, DROEBITI
RANDOM DROEBITI

/Henrik.

[CuriousOne]

Yes but same code run on 16F870 gives great random numbers?

[HenrikOlsson]

Does it really? You're going to have to convince me on that one ;-)
As far as I understand that's pretty much impossible. Give RANDOM a specific seed and you'll get a specific sequency of "random" number from it. Next time you run it, given the same seed, you'll get the same sequence of numbers.

/Henrik.

[CuriousOne]

I can film a video, if you like

[HenrikOlsson]

You could, if you want to, or just post the code (not just the snippet above) for the 16F870 and two or three sequences of the result you're getting.

/Henrik.

[wdmagic]

I have found that just about all random number generators on pics, and PCs generate the same it has to do with seed values.
my solution was to have it generate random numbers repeatedly very fast (on a timer) and have the program grab numberswhen needed. instead of calling for a random number, your calling for whatever number is currently being generated.

[peterdeco1]

A while back I had issues generating random numbers. Each time a pushbutton was pushed I needed a random number which very often repeated the same sequence. I did the following. It was also checking a port for a button push while generating numbers and did a specific task depending on the number.

START:
LET NUMBER = (NUMBER + 1)
IF NUMBER >=250 Then LET NUMBER = 0
GOTO START

[ruijc]

If you have spare pins, use one ADC pin to capture nothing but noise and that will give you your random number.

Always different for sure