Fix Serial.flush() blocking if called immediately after Serial.begin().

rocketscream · sandeepmistry · commit bfd2a0bb28f7 · 2016-05-30T11:54:18.000-04:00
diff --git a/cores/arduino/SERCOM.cpp b/cores/arduino/SERCOM.cpp
@@ -104,6 +104,8 @@ void SERCOM::enableUART()
 
 void SERCOM::flushUART()
 {
+  // Skip checking transmission completion if data register is empty
+  if(isDataRegisterEmptyUART()) return;
   // Wait for transmission to complete
   while(!sercom->USART.INTFLAG.bit.TXC);
 }

Original file line number	Diff line number	Diff line change
`@@ -104,6 +104,8 @@ void SERCOM::enableUART()`
`104`	`104`
`105`	`105`	`void SERCOM::flushUART()`
`106`	`106`	`{`
	`107`	`+ // Skip checking transmission completion if data register is empty`
	`108`	`+ if(isDataRegisterEmptyUART()) return;`
`107`	`109`	`// Wait for transmission to complete`
`108`	`110`	`while(!sercom->USART.INTFLAG.bit.TXC);`
`109`	`111`	`}`