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Pseudo Random Number Generator using 8bit MCU ?

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psubiaco

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8 bit pseudorandom c

Could anybody send me any idea to have a sequence of 8bit random numbers?
My idea was to start from a SEED and every fix period (timer interrupt routine) update this number obtaing a pseudo random sequence.
I found some example about "how to generate a stream of bits" or "how to generate a single number", but I've not find, yet, a routine to create a stream of 8bit numbers, and I don't know the theory of RNG. :cry:

Any C source code example or alghorithm is welcome.
Thank you in advance. Paolo
 

mcu random generator

Here is simple implementation from one of my previous projects:

Code: 
U16 RND_Num;      // Current random number

// Initialize random number generator
void SRV_InitRnd(void) {
    RND_Num=12345; // Here is initial seed comes
}

// Returns random number from 0 to (max-1)
U16 SRV_Rnd(U16 max) {
    U16 i,j;
    i=RND_Num>>8;
    j=RND_Num&0xFF;
    i=i*18273+j;
    j=j*29379+i;
    RND_Num=((i&0xFF)<<8)|(j&0xFF);
    return (RND_Num%max);
}

Ace-X.
 

8051 8-bit random generator

I cannot try this routine due to MCU limitation (8bit holtek MCU), but I wonder if the same function should be applied to an 8 bit random number.
So, splitting the random byte into 2 nibbles which should be multiplied by little numbers, then shifted and ORed forming the new random number.

Now, I'm using this function, but I don't know how good is the sequence generated by this algorithm, because it is absolutely casual (written by me, which don't know anything about coding.

Code: 
void random_next() {
  // shift random left, and put b0(n+1)=b4(n)^b7(n)
  randomtmp=0;
  if (random&0x10) { // extract bit 4
    randomtmp++;
  }
  // randomtmp==1 if bit4 of random ==1
  _c=0;  // _c is the carry
  _rlc(&random);  // rotate left through carry
  if (_c) randomtmp^=1;
  random^=randomtmp;
}

Thank you! Paolo
 

8 bit random number generator

There is a lot of implementation to generate pseudorandom numbers implementin a cellular automata. I want to help you but i donot remmeber how to make it.
 

PSoC microcontrollers can have hardware realization of PRN generator in their programmable blocks.

•2- to 8-, 16-, 24- or 32-bit general purpose pseudo-random number generator uses one, two, three or four PSoC blocks, respectively

•Data input clocking up to 48 MHz

•Programmable polynomial and seed values

•Serial output bit stream

•Computed pseudo-random number can be read directly from the LFSR

Here is one application note:
https://www.cypress.com/support/app...Array&tid=A47EC41D-A212-4D8B-B3AA620F3AEB2978
 

psubiaco said:
I cannot try this routine due to MCU limitation (8bit holtek MCU), but I wonder if the same function should be applied to an 8 bit random number.
Click to expand...

It is actually for 8-bit uC (8051) - usually 16-bits numbers are automatically handled by C compiler for uC. To get 8-bit number you can just get the last 8 bits of 16-bits PRN.

psubiaco said:
Now, I'm using this function, but I don't know how good is the sequence generated by this algorithm, because it is absolutely casual (written by me, which don't know anything about coding.
Click to expand...

You can use DieHard test suite for testing quality of PRNG. It is free and can be found at **broken link removed**.

Good luck!

Ace-X.
 

The simple way to generate the Pseudo Random Number is using M-Sequency initial with a seed.

attached is a MCU example and 24 stage M-sequency.
 

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