From b0ba604ba5ab1ba866df71b7e11099a3b1ceee3f Mon Sep 17 00:00:00 2001
From: Badr Bouslikhin <bouslikhin.badr@gmail.com>
Date: Fri, 7 Mar 2025 18:00:52 +0100
Subject: [PATCH] fix(stm32): handle half-duplex in ringbuffered read

---
 embassy-stm32/src/usart/mod.rs          |  1 -
 embassy-stm32/src/usart/ringbuffered.rs | 10 ++++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/embassy-stm32/src/usart/mod.rs b/embassy-stm32/src/usart/mod.rs
index 5b7f8dc26..10e3ea88b 100644
--- a/embassy-stm32/src/usart/mod.rs
+++ b/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
diff --git a/embassy-stm32/src/usart/ringbuffered.rs b/embassy-stm32/src/usart/ringbuffered.rs
index 8e42d5917..eaa9424c5 100644
--- a/embassy-stm32/src/usart/ringbuffered.rs
+++ b/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, _)) => {}