Generating external noise from analog in like on arduino

#1

If i left analog in 0 unconnected on the ardunino, i could use the pin to create "real" random values.
How to do that with an Axoloti?
Is there a noise circuit for 3.3 volt ?

#2

try using math/<< with big values (like maybe 6-7, not sure what's the signal/noise ratio on gpio) on a gpio/in/analog

#3

Also you could put a math/delta before the bitshift object in order to eliminate dc

#4

also, if you put a math/smooth after the bitshift (but you'll have to bitshift a lot more) you can get a higher resolution noise.

The only problem with this kind of noise is that it picks up a lot of hum from the power supply, i noticed it plugging the power supply of my laptop.. there's no band reject filter that cancels that.

I also noticed that different gpio pads pick up different noise (which always comprises power hum).

#5

Since software version 1.0.11, Axoloti makes use of the hardware random number generator inside the processor, and objects use that.

From the processor documentation (RM0090):

The random number generator implements an analog circuit. This circuit generates seeds
that feed a linear feedback shift register (RNG_LFSR) in order to produce 32-bit random
numbers.
The analog circuit is made of several ring oscillators whose outputs are XORed to generate
the seeds.

One implementation note (from firmware/axoloti_math.h):
The hardware random generator can't provide new data as quick as desirable, but rather than waiting for a new true random number, we multiply/add the seed with the latest hardware-generated number.

That 'd make it unsuitable for cryptographic purposes. but for all other applications, I doubt you'd notice.

#6

Dear Sputniki thanks for investigations!!!
@johannes how did you know, that i would need this for cryptographic purposes?
gpio noise.axp (24.9 KB)
for me the magic of noise from a diode/transistor is still unbeatable, because its not

but atmospherical interferencies influencing some electrons to jump aka commit sucide while others choose to stay alive, thats where the magic happens.....
Btw ....could i add an antenna to the axolti? like the theremin, but for alien signals?

#7

The hardware random generator also uses "suicide electrons" to generate random, balanced out to avoid any patterns, still magic noise from transistors.

I made some undocumented attempts to do theremin-like sensing with a minimum of external components, but I did not obtain a good distance sensing range. Alien signals, astronomers use huge radio telescope dishes but still aren't sure. To receive "local aliens" maybe check the elektor tapir project.

#8

hmm i will test this with batteries, wich would be helpful for this too
https://sebiik.github.io/community.axoloti.com.backup/t/how-to-interface-axoloti-with-plants-midi-sprout-300/1772
as i understand you, i also could amplify any analog input wiith the bitshift object to my needs!?

and with a power bank i could eliminate the hummings...!

#9

elektor tapir
Totally Archaic but Practical Interceptor of Radiation