From e008cc8da151fae30760fbe4cae4c9cb9984d554 Mon Sep 17 00:00:00 2001
From: BlackMark <me@blackmark.me>
Date: Wed, 25 May 2016 01:40:53 +0200
Subject: [PATCH] Fixed flushing receive buffer to work independent of baud
 rate and with and without interrupts

---
 usart.cpp | 41 ++++++++++++++++++++++++++++++++++-------
 usart.h   |  4 ++--
 2 files changed, 36 insertions(+), 9 deletions(-)

diff --git a/usart.cpp b/usart.cpp
index b451df5..82d72cf 100644
--- a/usart.cpp
+++ b/usart.cpp
@@ -300,7 +300,7 @@ bool USART0::receiveByte( uint8_t &ui8Data, uint16_t ui16TimeoutMS )
 	{
 		_delay_ms( 1 );
 
-		if( ui16DelayCounter++ >= ui16TimeoutMS )
+		if( ui16DelayCounter++ > ui16TimeoutMS )
 		{
 			return false;
 		}
@@ -336,14 +336,41 @@ void USART0::flushReceive()
 {
 	uint8_t ui8Received;
 
-	while( m_vsizeRXBufferHead != m_vsizeRXBufferTail )
-	{
-		receiveByte( ui8Received );
-	}
+	uint16_t ui16UBRR;
+	ui16UBRR = static_cast<uint16_t>( *m_vui8pUBRRH ) << 8;
+	ui16UBRR |= *m_vui8pUBRRL;
 
-	if( !( SREG & ( 1 << SREG_I ) ) && ( *m_vui8pUCSRA & ( 1 << RXC_D ) ) )
+	uint8_t ui8BitsPerSymbol = 10;
+
+	uint16_t ui16BaudDelayMS = static_cast<uint16_t>( ui8BitsPerSymbol * ( 16 * ( ui16UBRR + 1.0 ) ) / ( F_CPU / 1000.0 ) ) + 1;
+
+	if( !( SREG & ( 1 << SREG_I ) ) )
 	{
-		ui8Received = *m_vui8pUDR;
+		while( true )
+		{
+			for( uint16_t i = 0; i < ui16BaudDelayMS; ++i )
+			{
+				_delay_ms( 1 );
+			}
+
+			if( m_vsizeRXBufferHead != m_vsizeRXBufferTail )
+			{
+				receiveByte( ui8Received );
+				continue;
+			}
+
+			if( ( *m_vui8pUCSRA & ( 1 << RXC_D ) ) )
+			{
+				ui8Received = *m_vui8pUDR;
+				continue;
+			}
+
+			break;
+		}
+	}
+	else
+	{
+		while( receiveByte( ui8Received, ui16BaudDelayMS ) );
 	}
 }
 
diff --git a/usart.h b/usart.h
index 485347c..1d7ba01 100644
--- a/usart.h
+++ b/usart.h
@@ -1,7 +1,7 @@
 /*
 * Copyright (c) by BlackMark 2015-2016
-* Date 24/05/2016
-* Version 2.9
+* Date 25/05/2016
+* Version 3.0
 */
 
 #ifndef USART_H