Notes

Randomness via an ADC

A much higher level of randomness can be obtained by observing some aspect of the real physical world, and capturing a noisy signal (“noise” == “random” in physics … sort of).

With an ADC, this is easy to do: leave one ADC input pin floating, and measure its analog voltage. The least-significant bit will be the noisiest, always fluctuating due to electrical noise, e.g. the omni-present thermal brownian motion. If we repeat this 32 times and keep only the lower bit, we should get nicely random results:

ADC<0> adc;
PinA<0> floatingPin;

uint32_t randomNumber () {
    uint32_t r = 0;
    for (int i = 0; i < 32; ++i)
        r = (r << 1) | (adc.read(floatingPin) & 1);
    return r;
}

https://jeelabs.org/2018/random-numbers/

alias pru='pio run -t upload'

[env:bluepill]
platform = ststm32
board = bluepill_f103c8
framework = stm32cube
upload_protocol = blackmagic
upload_port = /dev/cu.usbmodemE0C2C5A7
lib_deps = jeeh

pio device monitor --quiet -b 115200 -p /dev/cu.usbmodem469

picocom -q -b 115200 --imap lfcrlf /dev/cu.usbmodem469

https://jeelabs.org/2018/getting-started-bp/

https://github.com/gd32v-rust/gd32vf103-example

https://how2electronics.com/interfacing-ds18b20-temperature-sensor-with-stm32/