Struct esp32_hal::FlashSafeDma

pub struct FlashSafeDma<T, const SIZE: usize> { /* private fields */ }

FlashSafeDma

The embedded-hal traits make no guarantees about where the buffers are placed. The DMA implementation in Espressif chips has a limitation in that it can only access the RAM address space, meaning data to be transmitted from the flash address space must be copied into RAM first.

This wrapper struct should be used when a peripheral using the DMA engine needs to transmit data from flash (ROM) via the embedded-hal traits. This is often a const variable.

Example usage using spi::master::dma::SpiDma

const ARRAY_IN_FLASH = [0xAA; 128]

let spi = SpiDma::new(/* */);

spi.write(&ARRAY_IN_FLASH[..]).unwrap(); // error when transmission starts

let spi = FlashSafeDma::new(spi);

spi.write(&ARRAY_IN_FLASH[..]).unwrap(); // success

Implementations

impl<T, const SIZE: usize> FlashSafeDma<T, SIZE>

pub fn new(inner: T) -> FlashSafeDma<T, SIZE>

pub fn inner_mut(&mut self) -> &mut T

pub fn inner(&self) -> &T

pub fn free(self) -> T

Trait Implementations

impl<T, const SIZE: usize> Transfer<u8> for FlashSafeDma<T, SIZE>

where T: Transfer<u8>,

type Error = <T as Transfer<u8>>::Error

Error type

fn transfer<'w>( &mut self, words: &'w mut [u8] ) -> Result<&'w [u8], <FlashSafeDma<T, SIZE> as Transfer<u8>>::Error>

Sends words to the slave. Returns the words received from the slave

impl<T, const SIZE: usize> Write<u8> for FlashSafeDma<T, SIZE>

where T: Write<u8>,

type Error = <T as Write<u8>>::Error

Error type

fn write( &mut self, words: &[u8] ) -> Result<(), <FlashSafeDma<T, SIZE> as Write<u8>>::Error>

Sends words to the slave, ignoring all the incoming words

impl<T, const SIZE: usize> FullDuplex<u8> for FlashSafeDma<T, SIZE>

where T: FullDuplex<u8>, FlashSafeDma<T, SIZE>: Transfer<u8, Error = <T as FullDuplex<u8>>::Error> + Write<u8, Error = <T as FullDuplex<u8>>::Error>,

type Error = <T as FullDuplex<u8>>::Error

An enumeration of SPI errors

fn read( &mut self ) -> Result<u8, Error<<FlashSafeDma<T, SIZE> as FullDuplex<u8>>::Error>>

Reads the word stored in the shift register

fn send( &mut self, word: u8 ) -> Result<(), Error<<FlashSafeDma<T, SIZE> as FullDuplex<u8>>::Error>>

Sends a word to the slave