fix(stm32): handle half-duplex in ringbuffered read

embassy-stm32/src/usart/mod.rs

@@ -711,7 +711,6 @@ impl<'d> UartRx<'d, Async> {
 
         // make sure USART state is restored to neutral state when this future is dropped
         let on_drop = OnDrop::new(move || {
-            // defmt::trace!("Clear all USART interrupts and DMA Read Request");
             // clear all interrupts and DMA Rx Request
             r.cr1().modify(|w| {
                 // disable RXNE interrupt

embassy-stm32/src/usart/ringbuffered.rs

@@ -150,6 +150,16 @@ impl<'d> RingBufferedUartRx<'d> {
     pub async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Error> {
         self.start_dma_or_check_errors()?;
 
+        // In half-duplex mode, we need to disable the Transmitter and enable the Receiver
+        // since they can't operate simultaneously on the shared line
+        let r = self.info.regs;
+        if r.cr3().read().hdsel() && r.cr1().read().te() {
+            r.cr1().modify(|reg| {
+                reg.set_re(true);
+                reg.set_te(false);
+            });
+        }
+
         loop {
             match self.ring_buf.read(buf) {
                 Ok((0, _)) => {}