2 files changed, 53 insertions, 11 deletions

diff --git a/Projects/USBtoSerial/Lib/LightweightRingBuff.h b/Projects/USBtoSerial/Lib/LightweightRingBuff.h
index 1dc05935c..9c25707b4 100644
--- a/Projects/USBtoSerial/Lib/LightweightRingBuff.h
+++ b/Projects/USBtoSerial/Lib/LightweightRingBuff.h
@@ -75,12 +75,12 @@
 			Buffer->Count = 0;
 		}
 		
-		/** Inserts an element into the ring buffer.
+		/** Atomically inserts an element into the ring buffer.
 		 *
 		 *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into
 		 *  \param[in]     Data    Data element to insert into the buffer
 		 */
-		static inline void RingBuffer_Insert(RingBuff_t* const Buffer, RingBuff_Data_t Data)
+		static inline void RingBuffer_AtomicInsert(RingBuff_t* const Buffer, RingBuff_Data_t Data)
 		{
 			ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
 			{
@@ -93,13 +93,13 @@
 			}
 		}
 
-		/** Retrieves an element from the ring buffer.
+		/** Atomically retrieves an element from the ring buffer.
 		 *
 		 *  \param[in,out] Buffer  Pointer to a ring buffer structure to retrieve from
 		 *
 		 *  \return Next data element stored in the buffer
 		 */
-		static inline RingBuff_Data_t RingBuffer_Remove(RingBuff_t* const Buffer)
+		static inline RingBuff_Data_t RingBuffer_AtomicRemove(RingBuff_t* const Buffer)
 		{
 			RingBuff_Data_t Data;
 			
@@ -116,5 +116,38 @@
 			return Data;
 		}
 
+		/** Inserts an element into the ring buffer.
+		 *
+		 *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into
+		 *  \param[in]     Data    Data element to insert into the buffer
+		 */
+		static inline void RingBuffer_Insert(RingBuff_t* const Buffer, RingBuff_Data_t Data)
+		{
+			*Buffer->In = Data;
+			
+			if (++Buffer->In == &Buffer->Buffer[BUFFER_SIZE])
+			  Buffer->In = Buffer->Buffer;
+				  
+			Buffer->Count++;
+		}
+
+		/** Retrieves an element from the ring buffer.
+		 *
+		 *  \param[in,out] Buffer  Pointer to a ring buffer structure to retrieve from
+		 *
+		 *  \return Next data element stored in the buffer
+		 */
+		static inline RingBuff_Data_t RingBuffer_Remove(RingBuff_t* const Buffer)
+		{
+			RingBuff_Data_t Data = *Buffer->Out;
+			
+			if (++Buffer->Out == &Buffer->Buffer[BUFFER_SIZE])
+			  Buffer->Out = Buffer->Buffer;
+				  
+			Buffer->Count--;
+
+			return Data;
+		}
+
 #endif
  
\ No newline at end of file
diff --git a/Projects/USBtoSerial/USBtoSerial.c b/Projects/USBtoSerial/USBtoSerial.c
index 7a0f6866a..918986883 100644
--- a/Projects/USBtoSerial/USBtoSerial.c
+++ b/Projects/USBtoSerial/USBtoSerial.c
@@ -87,16 +87,22 @@ int main(void)
 			if (!(BUFFER_SIZE - USBtoUSART_Buffer.Count))
 			  break;
 			  
-			RingBuffer_Insert(&USBtoUSART_Buffer, CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface));
+			RingBuffer_AtomicInsert(&USBtoUSART_Buffer, CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface));
 		}
 		
-		/* Read bytes from the USART receive buffer into the USB IN endpoint */
-		while (USARTtoUSB_Buffer.Count)
-		  CDC_Device_SendByte(&VirtualSerial_CDC_Interface, RingBuffer_Remove(&USARTtoUSB_Buffer));
+		/* Check if the software USART flush timer has expired */
+		if (TIFR0 & (1 << TOV0))
+		{
+			TIFR0 |= (1 << TOV0);
+
+			/* Read bytes from the USART receive buffer into the USB IN endpoint */
+			while (USARTtoUSB_Buffer.Count)
+			  CDC_Device_SendByte(&VirtualSerial_CDC_Interface, RingBuffer_AtomicRemove(&USARTtoUSB_Buffer));
+		}
 		
-		/* Load bytes from the USART transmit buffer into the USART */
-		while (USBtoUSART_Buffer.Count)
-		  Serial_TxByte(RingBuffer_Remove(&USBtoUSART_Buffer));
+		/* Load the next byte from the USART transmit buffer into the USART */
+		if (USBtoUSART_Buffer.Count)
+		  Serial_TxByte(RingBuffer_AtomicRemove(&USBtoUSART_Buffer));
 		
 		CDC_Device_USBTask(&VirtualSerial_CDC_Interface);
 		USB_USBTask();
@@ -117,6 +123,9 @@ void SetupHardware(void)
 	Serial_Init(9600, false);
 	LEDs_Init();
 	USB_Init();
+
+	/* Configure the UART flush timer - run at Fcpu/1024 for maximum interval before overflow */
+	TCCR0B = ((1 << CS02) | (1 << CS00));
 }
 
 /** Event handler for the library USB Connection event. */