stm32/uart impl ReadReady for RingbufferdUart

embassy-stm32/src/usart/mod.rs

@@ -260,6 +260,8 @@ pub enum Error {
     Parity,
     /// Buffer too large for DMA
     BufferTooLong,
+    // TODO: ask what this is and document it (dvdsk)
+    DmaUnsynced,
 }
 
 enum ReadCompletionEvent {
@@ -1689,6 +1691,7 @@ impl embedded_hal_nb::serial::Error for Error {
             Self::Overrun => embedded_hal_nb::serial::ErrorKind::Overrun,
             Self::Parity => embedded_hal_nb::serial::ErrorKind::Parity,
             Self::BufferTooLong => embedded_hal_nb::serial::ErrorKind::Other,
+            Self::DmaUnsynced => embedded_hal_nb::serial::ErrorKind::Other,
         }
     }
 }

embassy-stm32/src/usart/ringbuffered.rs

@@ -5,6 +5,7 @@ use core::task::Poll;
 
 use embassy_embedded_hal::SetConfig;
 use embassy_hal_internal::PeripheralRef;
+use embedded_io_async::ReadReady;
 use futures_util::future::{select, Either};
 
 use super::{clear_interrupt_flags, rdr, reconfigure, sr, Config, ConfigError, Error, Info, State, UartRx};
@@ -262,3 +263,13 @@ impl embedded_io_async::Read for RingBufferedUartRx<'_> {
         self.read(buf).await
     }
 }
+
+impl ReadReady for RingBufferedUartRx<'_> {
+    fn read_ready(&mut self) -> Result<bool, Self::Error> {
+        let len = self.ring_buf.len().map_err(|e| match e {
+            crate::dma::ringbuffer::Error::Overrun => Self::Error::Overrun,
+            crate::dma::ringbuffer::Error::DmaUnsynced => Self::Error::DmaUnsynced,
+        })?;
+        Ok(len > 0)
+    }
+}