improvements for UART API

va416xx-hal/src/uart.rs

@@ -1201,10 +1201,20 @@ impl<Uart: Instance> embedded_hal_nb::serial::Read<u8> for UartBase<Uart> {
 
 impl<Uart: Instance> embedded_hal_nb::serial::Write<u8> for UartBase<Uart> {
     fn write(&mut self, word: u8) -> nb::Result<(), Self::Error> {
-        self.tx.write(word)
+        self.tx.write(word).map_err(|e| {
+            if let nb::Error::Other(_) = e {
+                unreachable!()
+            }
+            nb::Error::WouldBlock
+        })
     }
 
     fn flush(&mut self) -> nb::Result<(), Self::Error> {
-        self.tx.flush()
+        self.tx.flush().map_err(|e| {
+            if let nb::Error::Other(_) = e {
+                unreachable!()
+            }
+            nb::Error::WouldBlock
+        })
     }
 }