fix: SoftwareSerial flush() issue

gicking · fpistm · commit cde84d7acf76 · 2026-01-29T09:04:08.000+01:00
Fixes #2904. Signed-off-by: gicking <icking@onlinehome.de>
diff --git a/libraries/SoftwareSerial/src/SoftwareSerial.cpp b/libraries/SoftwareSerial/src/SoftwareSerial.cpp
@@ -409,6 +409,8 @@ void SoftwareSerial::flush()
   noInterrupts();
   _receive_buffer_head = _receive_buffer_tail = 0;
   interrupts();
+  // wait for previous transmit to complete
+  while (active_out);
 }
 
 int SoftwareSerial::peek()

Original file line number	Diff line number	Diff line change
`@@ -409,6 +409,8 @@ void SoftwareSerial::flush()`
`409`	`409`	`noInterrupts();`
`410`	`410`	`_receive_buffer_head = _receive_buffer_tail = 0;`
`411`	`411`	`interrupts();`
	`412`	`+ // wait for previous transmit to complete`
	`413`	`+ while (active_out);`
`412`	`414`	`}`
`413`	`415`
`414`	`416`	`int SoftwareSerial::peek()`