f2b59538df
* Add RNG to list of peripherals to be created * Refactor RNG driver to use PeripheralRef
65 lines
2.1 KiB
Rust
65 lines
2.1 KiB
Rust
//! Random number generator driver
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use core::convert::Infallible;
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use embedded_hal::blocking::rng::Read;
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use crate::{
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peripheral::{Peripheral, PeripheralRef},
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peripherals::RNG,
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};
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/// Random Number Generator
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///
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/// It should be noted that there are certain pre-conditions which must be met
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/// in order for the RNG to produce *true* random numbers. The hardware RNG
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/// produces true random numbers under any of the following conditions:
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///
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/// - RF subsystem is enabled (i.e. Wi-Fi or Bluetooth are enabled).
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/// - An internal entropy source has been enabled by calling
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/// `bootloader_random_enable()` and not yet disabled by calling
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/// `bootloader_random_disable()`.
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/// - While the ESP-IDF Second stage bootloader is running. This is because the
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/// default ESP-IDF bootloader implementation calls
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/// `bootloader_random_enable()` when the bootloader starts, and
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/// `bootloader_random_disable()` before executing the app.
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///
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/// When any of these conditions are true, samples of physical noise are
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/// continuously mixed into the internal hardware RNG state to provide entropy.
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/// If none of the above conditions are true, the output of the RNG should be
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/// considered pseudo-random only.
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///
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/// For more information, please refer to the ESP-IDF documentation:
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/// <https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/system/random.html>
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pub struct Rng<'d> {
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rng: PeripheralRef<'d, RNG>,
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}
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impl<'d> Rng<'d> {
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/// Create a new random number generator instance
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pub fn new(rng: impl Peripheral<P = RNG> + 'd) -> Self {
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crate::into_ref!(rng);
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Self { rng }
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}
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#[inline]
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/// Reads currently available `u32` integer from `RNG`
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pub fn random(&mut self) -> u32 {
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self.rng.data.read().bits()
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}
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}
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impl Read for Rng<'_> {
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type Error = Infallible;
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fn read(&mut self, buffer: &mut [u8]) -> Result<(), Self::Error> {
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for chunk in buffer.chunks_mut(4) {
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let bytes = self.random().to_le_bytes();
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chunk.copy_from_slice(&bytes[..chunk.len()]);
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}
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Ok(())
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}
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}
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