Fix flash error flag clearing

According to the STM32F10xxx Flash programming manual [(PM0068, p22)](https://www.st.com/resource/en/programming_manual/pm0068-stm32f10xxx-xldensity-flash-programming-stmicroelectronics.pdf),
WRPRTERR and PGERR flags are cleared by writing 1. The original code
incorrectly attempted to clear these flags by writing 0, causing them
to remain set after an error occurred. This prevented further flash
operations until reset.

This commit corrects the flag clearing operation, allowing flash
operations to continue after recoverable errors.

Author: nhpupu

CHANGELOG.md

@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Replace UB code by a legitimate pointer access
 - Reexport `Direction` from `qei`
 - Add dac
+- Fix flash error flag clearing
 
 ## [v0.10.0] - 2022-12-12
 

src/flash.rs

@@ -166,7 +166,8 @@ impl<'a> FlashWriter<'a> {
         self.lock()?;
 
         if sr.wrprterr().bit_is_set() {
-            self.flash.sr.sr().modify(|_, w| w.wrprterr().clear_bit());
+            // reset by writing 1
+            self.flash.sr.sr().modify(|_, w| w.wrprterr().bit(true));
             Err(Error::EraseError)
         } else {
             if self.verify {
@@ -257,12 +258,14 @@ impl<'a> FlashWriter<'a> {
 
             // Check for errors
             if self.flash.sr.sr().read().pgerr().bit_is_set() {
-                self.flash.sr.sr().modify(|_, w| w.pgerr().clear_bit());
+                // reset by writing 1
+                self.flash.sr.sr().modify(|_, w| w.pgerr().bit(true));
 
                 self.lock()?;
                 return Err(Error::ProgrammingError);
             } else if self.flash.sr.sr().read().wrprterr().bit_is_set() {
-                self.flash.sr.sr().modify(|_, w| w.wrprterr().clear_bit());
+                // reset by writing 1
+                self.flash.sr.sr().modify(|_, w| w.wrprterr().bit(true));
 
                 self.lock()?;
                 return Err(Error::WriteError);