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Merge pull request #2739 from adri326/adri326/nodma-embedded-io

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Provide embedded_io impls for Uart with and without Dma
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Dario Nieuwenhuis 2024-03-27 14:47:19 +00:00 committed by GitHub
commit a678b4850c
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1 changed files with 41 additions and 5 deletions
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46
embassy-stm32/src/usart/mod.rs
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@ -209,7 +209,14 @@ enum ReadCompletionEvent {
Idle(usize),
}
/// Bidirectional UART Driver
/// Bidirectional UART Driver, which acts as a combination of [`UartTx`] and [`UartRx`].
///
/// ### Notes on [`embedded_io::Read`]
///
/// `embedded_io::Read` requires guarantees that the base [`UartRx`] cannot provide.
///
/// See [`UartRx`] for more details, and see [`BufferedUart`] and [`RingBufferedUartRx`]
/// as alternatives that do provide the necessary guarantees for `embedded_io::Read`.
pub struct Uart<'d, T: BasicInstance, TxDma = NoDma, RxDma = NoDma> {
tx: UartTx<'d, T, TxDma>,
rx: UartRx<'d, T, RxDma>,
@ -225,7 +232,10 @@ impl<'d, T: BasicInstance, TxDma, RxDma> SetConfig for Uart<'d, T, TxDma, RxDma>
}
}
/// Tx-only UART Driver
/// Tx-only UART Driver.
///
/// Can be obtained from [`Uart::split`], or can be constructed independently,
/// if you do not need the receiving half of the driver.
pub struct UartTx<'d, T: BasicInstance, TxDma = NoDma> {
phantom: PhantomData<&'d mut T>,
tx_dma: PeripheralRef<'d, TxDma>,
@ -240,7 +250,35 @@ impl<'d, T: BasicInstance, TxDma> SetConfig for UartTx<'d, T, TxDma> {
}
}
/// Rx-only UART Driver
/// Rx-only UART Driver.
///
/// Can be obtained from [`Uart::split`], or can be constructed independently,
/// if you do not need the transmitting half of the driver.
///
/// ### Notes on [`embedded_io::Read`]
///
/// `embedded_io::Read` requires guarantees that this struct cannot provide:
///
/// - Any data received between calls to [`UartRx::read`] or [`UartRx::blocking_read`]
/// will be thrown away, as `UartRx` is unbuffered.
/// Users of `embedded_io::Read` are likely to not expect this behavior
/// (for instance if they read multiple small chunks in a row).
/// - [`UartRx::read`] and [`UartRx::blocking_read`] only return once the entire buffer has been
/// filled, whereas `embedded_io::Read` requires us to fill the buffer with what we already
/// received, and only block/wait until the first byte arrived.
/// <br />
/// While [`UartRx::read_until_idle`] does return early, it will still eagerly wait for data until
/// the buffer is full or no data has been transmitted in a while,
/// which may not be what users of `embedded_io::Read` expect.
///
/// [`UartRx::into_ring_buffered`] can be called to equip `UartRx` with a buffer,
/// that it can then use to store data received between calls to `read`,
/// provided you are using DMA already.
///
/// Alternatively, you can use [`BufferedUartRx`], which is interrupt-based and which can also
/// store data received between calls.
///
/// Also see [this github comment](https://github.com/embassy-rs/embassy/pull/2185#issuecomment-1810047043).
pub struct UartRx<'d, T: BasicInstance, RxDma = NoDma> {
_peri: PeripheralRef<'d, T>,
rx_dma: PeripheralRef<'d, RxDma>,
@ -1260,7 +1298,6 @@ where
impl<T, TxDma, RxDma> embedded_io::Write for Uart<'_, T, TxDma, RxDma>
where
T: BasicInstance,
TxDma: crate::usart::TxDma<T>,
{
fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
self.blocking_write(buf)?;
@ -1275,7 +1312,6 @@ where
impl<T, TxDma> embedded_io::Write for UartTx<'_, T, TxDma>
where
T: BasicInstance,
TxDma: crate::usart::TxDma<T>,
{
fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
self.blocking_write(buf)?;