Clear error flags before returning

Closes #61

Signed-off-by: Daniel Egger <daniel@eggers-club.de>

CHANGELOG.md

@@ -43,6 +43,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Changed
 
+- Clear error flags in serial read() before returning
 - Revised feature flags for HSI48 clock support
 
 ## [v0.14.0] - 2019-04-25

src/serial.rs

@@ -571,16 +571,22 @@ fn read(usart: *const SerialRegisterBlock) -> nb::Result<u8, Error> {
     // NOTE(unsafe) atomic read with no side effects
     let isr = unsafe { (*usart).isr.read() };
 
+    // NOTE(unsafe) write accessor for atomic writes with no side effects
+    let icr = unsafe { &(*usart).icr };
+
     let err = if isr.pe().bit_is_set() {
+        icr.write(|w| w.pecf().set_bit());
         nb::Error::Other(Error::Parity)
     } else if isr.fe().bit_is_set() {
+        icr.write(|w| w.fecf().set_bit());
         nb::Error::Other(Error::Framing)
     } else if isr.nf().bit_is_set() {
+        icr.write(|w| w.ncf().set_bit());
         nb::Error::Other(Error::Noise)
     } else if isr.ore().bit_is_set() {
+        icr.write(|w| w.orecf().set_bit());
         nb::Error::Other(Error::Overrun)
     } else if isr.rxne().bit_is_set() {
-        // NOTE(read_volatile) see `write_volatile` below
         return Ok(unsafe { ptr::read_volatile(&(*usart).rdr as *const _ as *const _) });
     } else {
         return Err(nb::Error::WouldBlock);