Pseudo Random Number Generator Project

I am required to design and build an 8 bit Pseudo Random Number Generator. I have looked at possible methods; using background noise, user input etc.开发者_如何学C I was wondering if anyone could give me some advice on where to start as this would be of great help to me.

random.org is perhaps the best place to start your investigation.

Below should get you started with the basics

1. howstuffworks.com
2. Construct your own random number generator

For a simple 8 bit PRNG you could ry something like a Linear Feedback Shift Register. This is very simple to implement in either software or hardware.

My plan is to use a temperature sensor. When the temps are being processed in the ADC, I am going to amplify the noise generated. This will then give me the random 8 bit number I require which will be used as the 'seed' for the PRNG in stdlib (C programming). What do you's think?

I've found that the following works very well. This is implemented in MSP430 assembly, but would be easy enough to port to another processor. I've used this to generate 'white' noise for a synthesizer project, and there were no audible patterns in the output. Depending on what your requirements are, this might be sufficient. It uses two state variables, the previous output (8 bits), and a 16-bit state register. I found this online, http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=95614&highlight=radbrad, where it's listed in AVR assembly, and ported it to MSP.

Because it uses shifts and shifts the top bit out of one register into the bottom of another, it doesn't really lend itself to efficient implementation in C. Hence the assembly. I hope you find this as useful as I did.

mov.b &rand_out, r13
mov.b r13,r12
and.b #66, r13
jz ClearCarry
cmp.b #66, r13
xor.w #1, sr ; invert carry flag
jmp SkipClearCarry
  ClearCarry:
clrc
  SkipClearCarry:
rlc.w &rand_state
rlc.b r12
mov.b r12,&rand_out
ret