Altered the CDC Deivice and Host Class drivers' receive byte routines, so that no data is indicated by a negative return value.

Added auto flushing of OUT data to the CDC Host Class driver's USBTask function to automatically flush the send pipe buffer.

Demos/Device/ClassDriver/DualVirtualSerial/DualVirtualSerial.c

@@ -101,12 +101,12 @@ int main(void)
 		CheckJoystickMovement();
 
 		/* Discard all received data on the first CDC interface */
-		while (CDC_Device_BytesReceived(&VirtualSerial1_CDC_Interface))
+		CDC_Device_ReceiveByte(&VirtualSerial1_CDC_Interface);
-		  CDC_Device_ReceiveByte(&VirtualSerial1_CDC_Interface);
 
 		/* Echo all received data on the second CDC interface */
-		while (CDC_Device_BytesReceived(&VirtualSerial2_CDC_Interface))
+		int16_t ReceivedByte; = CDC_Device_ReceiveByte(&VirtualSerial2_CDC_Interface);
-		  CDC_Device_SendByte(&VirtualSerial2_CDC_Interface, CDC_Device_ReceiveByte(&VirtualSerial2_CDC_Interface));
+		if (!(ReceivedByte < 0))
+		  CDC_Device_SendByte(&VirtualSerial2_CDC_Interface, (uint8_t)ReceivedByte);
 		  
 		CDC_Device_USBTask(&VirtualSerial1_CDC_Interface);
 		CDC_Device_USBTask(&VirtualSerial2_CDC_Interface);

Demos/Device/ClassDriver/VirtualSerial/VirtualSerial.c

@@ -83,8 +83,7 @@ int main(void)
 		CheckJoystickMovement();
 		 
 		/* Must throw away unused bytes from the host, or it will lock up while waiting for the device */
-		while (CDC_Device_BytesReceived(&VirtualSerial_CDC_Interface))
+		CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface);
-		  CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface);
 
 		CDC_Device_USBTask(&VirtualSerial_CDC_Interface);
 		USB_USBTask();

Demos/Device/ClassDriver/VirtualSerialMouse/VirtualSerialMouse.c

@@ -97,8 +97,7 @@ int main(void)
 		CheckJoystickMovement();
 		 
 		/* Must throw away unused bytes from the host, or it will lock up while waiting for the device */
-		while (CDC_Device_BytesReceived(&VirtualSerial_CDC_Interface))
+		CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface);
-		  CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface);
 
 		CDC_Device_USBTask(&VirtualSerial_CDC_Interface);
 		HID_Device_USBTask(&Mouse_HID_Interface);

Demos/Host/ClassDriver/VirtualSerialHost/VirtualSerialHost.c

@@ -111,10 +111,9 @@ int main(void)
 				if (CDC_Host_BytesReceived(&VirtualSerial_CDC_Interface))
 				{
 					/* Echo received bytes from the attached device through the USART */
-					while (CDC_Host_BytesReceived(&VirtualSerial_CDC_Interface))
+					int16_t ReceivedByte = CDC_Host_ReceiveByte(&VirtualSerial_CDC_Interface);
-					  putchar(CDC_Host_ReceiveByte(&VirtualSerial_CDC_Interface));
+					if (!(ReceivedByte < 0))
-					  
+					  putchar(ReceivedByte);
-					CDC_Host_Flush(&VirtualSerial_CDC_Interface);  
 				}
 			
 				break;

LUFA/Drivers/USB/Class/Device/CDC.c

@@ -128,11 +128,6 @@ void CDC_Device_USBTask(USB_ClassInfo_CDC_Device_t* const CDCInterfaceInfo)
 {
 	if ((USB_DeviceState != DEVICE_STATE_Configured) || !(CDCInterfaceInfo->State.LineEncoding.BaudRateBPS))
 	  return;
-
-	Endpoint_SelectEndpoint(CDCInterfaceInfo->Config.DataOUTEndpointNumber);
-
-	if (Endpoint_IsOUTReceived() && !(Endpoint_BytesInEndpoint()))
-	  Endpoint_ClearOUT();
 	  
 	CDC_Device_Flush(CDCInterfaceInfo);
 }
@@ -222,19 +217,24 @@ uint16_t CDC_Device_BytesReceived(USB_ClassInfo_CDC_Device_t* const CDCInterface
 	}
 }
 
-uint8_t CDC_Device_ReceiveByte(USB_ClassInfo_CDC_Device_t* const CDCInterfaceInfo)
+int16_t CDC_Device_ReceiveByte(USB_ClassInfo_CDC_Device_t* const CDCInterfaceInfo)
 {
+	uint8_t ReceivedByte = -1;
+
 	if ((USB_DeviceState != DEVICE_STATE_Configured) || !(CDCInterfaceInfo->State.LineEncoding.BaudRateBPS))
 	  return 0;
 
 	Endpoint_SelectEndpoint(CDCInterfaceInfo->Config.DataOUTEndpointNumber);
 	
-	uint8_t DataByte = Endpoint_Read_Byte();
+	if (!(Endpoint_IsOUTReceived()))
+	  return -1;
+	else if (Endpoint_BytesInEndpoint())
+	  ReceivedByte = Endpoint_Read_Byte();
 	
 	if (!(Endpoint_BytesInEndpoint()))
 	  Endpoint_ClearOUT();
-	  
+	
-	return DataByte;
+	return ReceivedByte;
 }
 
 void CDC_Device_SendControlLineStateChange(USB_ClassInfo_CDC_Device_t* const CDCInterfaceInfo)
@@ -282,24 +282,28 @@ static int CDC_Device_putchar(char c,
 
 static int CDC_Device_getchar(FILE* Stream)
 {
-	if (!(CDC_Device_BytesReceived((USB_ClassInfo_CDC_Device_t*)fdev_get_udata(Stream))))
+	int16_t ReceivedByte = CDC_Device_ReceiveByte((USB_ClassInfo_CDC_Device_t*)fdev_get_udata(Stream));
+
+	if (ReceivedByte < 0)
 	  return _FDEV_EOF;
 
-	return CDC_Device_ReceiveByte((USB_ClassInfo_CDC_Device_t*)fdev_get_udata(Stream));
+	return ReceivedByte;
 }
 
 static int CDC_Device_getchar_Blocking(FILE* Stream)
 {
-	while (!(CDC_Device_BytesReceived((USB_ClassInfo_CDC_Device_t*)fdev_get_udata(Stream))))
+	int16_t ReceivedByte;
+	
+	while ((ReceivedByte = CDC_Device_ReceiveByte((USB_ClassInfo_CDC_Device_t*)fdev_get_udata(Stream))) < 0)
 	{
 		if (USB_DeviceState == DEVICE_STATE_Unattached)
 		  return _FDEV_EOF;
 	
 		CDC_Device_USBTask((USB_ClassInfo_CDC_Device_t*)fdev_get_udata(Stream));
-		USB_USBTask();
+		USB_USBTask();	
 	}
 
-	return CDC_Device_ReceiveByte((USB_ClassInfo_CDC_Device_t*)fdev_get_udata(Stream));
+	return ReceivedByte;
 }
 
 #endif

LUFA/Drivers/USB/Class/Device/CDC.h

@@ -233,7 +233,10 @@
 			uint8_t CDC_Device_SendByte(USB_ClassInfo_CDC_Device_t* const CDCInterfaceInfo,
 			                            const uint8_t Data) ATTR_NON_NULL_PTR_ARG(1);
 			
-			/** Determines the number of bytes received by the CDC interface from the host, waiting to be read.
+			/** Determines the number of bytes received by the CDC interface from the host, waiting to be read. This indicates the number
+			 *  of bytes in the OUT endpoint bank only, and thus the number of calls to \ref CDC_Device_ReceiveByte() which are guaranteed to
+			 *  succeed immediately. If multiple bytes are to be received, they should be buffered by the user application, as the endpoint
+			 *  bank will not be released back to the USB controller until all bytes are read.
 			 *
 			 *  \pre This function must only be called when the Device state machine is in the DEVICE_STATE_Configured state or
 			 *       the call will fail.
@@ -245,17 +248,18 @@
 			uint16_t CDC_Device_BytesReceived(USB_ClassInfo_CDC_Device_t* const CDCInterfaceInfo) ATTR_NON_NULL_PTR_ARG(1);
 			
 			/** Reads a byte of data from the host. If no data is waiting to be read of if a USB host is not connected, the function
-			 *  returns 0. The \ref CDC_Device_BytesReceived() function should be queried before data is received to ensure that no data
+			 *  returns a negative value. The \ref CDC_Device_BytesReceived() function may be queried in advance to determine how many
-			 *  underflow occurs.
+			 *  bytes are currently buffered in the CDC interface's data receive endpoint bank, and thus how many repeated calls to this
+			 *  function which are guaranteed to succeed.
 			 *
 			 *  \pre This function must only be called when the Device state machine is in the DEVICE_STATE_Configured state or
 			 *       the call will fail.
 			 *
 			 *  \param[in,out] CDCInterfaceInfo  Pointer to a structure containing a CDC Class configuration and state.
 			 *
-			 *  \return Next received byte from the host, or 0 if no data received.
+			 *  \return Next received byte from the host, or a negative value if no data received.
 			 */
-			uint8_t CDC_Device_ReceiveByte(USB_ClassInfo_CDC_Device_t* const CDCInterfaceInfo) ATTR_NON_NULL_PTR_ARG(1);
+			int16_t CDC_Device_ReceiveByte(USB_ClassInfo_CDC_Device_t* const CDCInterfaceInfo) ATTR_NON_NULL_PTR_ARG(1);
 			
 			/** Flushes any data waiting to be sent, ensuring that the send buffer is cleared.
 			 *

LUFA/Drivers/USB/Class/Host/CDC.c

@@ -220,14 +220,19 @@ void CDC_Host_USBTask(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo)
 			                    sizeof(CDCInterfaceInfo->State.ControlLineStates.DeviceToHost),
 			                    NO_STREAM_CALLBACK);
 			
+			Pipe_ClearIN();
+
+			EVENT_CDC_Host_ControLineStateChanged(CDCInterfaceInfo);
+		}
+		else
+		{
+			Pipe_ClearIN();
 		}
-
-		Pipe_ClearIN();
-
-		EVENT_CDC_Host_ControLineStateChanged(CDCInterfaceInfo);
 	}
 	
 	Pipe_Freeze();
+
+	CDC_Host_Flush(CDCInterfaceInfo);
 }
 
 uint8_t CDC_Host_SetLineEncoding(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo)
@@ -353,9 +358,9 @@ uint16_t CDC_Host_BytesReceived(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo
 	}
 }
 
-uint8_t CDC_Host_ReceiveByte(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo)
+int16_t CDC_Host_ReceiveByte(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo)
 {
-	uint8_t ReceivedByte = 0;
+	uint8_t ReceivedByte = -1;
 
 	if ((USB_HostState != HOST_STATE_Configured) || !(CDCInterfaceInfo->State.IsActive))
 	  return 0;
@@ -364,11 +369,14 @@ uint8_t CDC_Host_ReceiveByte(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo)
 	Pipe_SetPipeToken(PIPE_TOKEN_IN);
 	Pipe_Unfreeze();
 
-	ReceivedByte = Pipe_Read_Byte();
+	if (!(Pipe_IsINReceived()))
-	
+	  return -1;
+	else if (Pipe_BytesInPipe())
+	  ReceivedByte = Pipe_Read_Byte();
+
 	if (!(Pipe_BytesInPipe()))
 	  Pipe_ClearIN();
-	
+		
 	Pipe_Freeze();
 	
 	return ReceivedByte;
@@ -426,15 +434,19 @@ static int CDC_Host_putchar(char c,
 
 static int CDC_Host_getchar(FILE* Stream)
 {
-	if (!(CDC_Host_BytesReceived((USB_ClassInfo_CDC_Host_t*)fdev_get_udata(Stream))))
+	int16_t ReceivedByte = CDC_Host_ReceiveByte((USB_ClassInfo_CDC_Host_t*)fdev_get_udata(Stream));
+
+	if (ReceivedByte < 0)
 	  return _FDEV_EOF;
 
-	return CDC_Host_ReceiveByte((USB_ClassInfo_CDC_Host_t*)fdev_get_udata(Stream));
+	return ReceivedByte;
 }
 
 static int CDC_Host_getchar_Blocking(FILE* Stream)
 {
-	while (!(CDC_Host_BytesReceived((USB_ClassInfo_CDC_Host_t*)fdev_get_udata(Stream))))
+	int16_t ReceivedByte;
+	
+	while ((ReceivedByte = CDC_Host_ReceiveByte((USB_ClassInfo_CDC_Host_t*)fdev_get_udata(Stream))) < 0)
 	{
 		if (USB_HostState == HOST_STATE_Unattached)
 		  return _FDEV_EOF;
@@ -443,7 +455,7 @@ static int CDC_Host_getchar_Blocking(FILE* Stream)
 		USB_USBTask();
 	}
 
-	return CDC_Host_ReceiveByte((USB_ClassInfo_CDC_Host_t*)fdev_get_udata(Stream));
+	return ReceivedByte;
 }
 
 void CDC_Host_Event_Stub(void)

LUFA/Drivers/USB/Class/Host/CDC.h

@@ -236,7 +236,10 @@
 			uint8_t CDC_Host_SendByte(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo,
 			                          const uint8_t Data) ATTR_NON_NULL_PTR_ARG(1);
 
-			/** Determines the number of bytes received by the CDC interface from the device, waiting to be read.
+			/** Determines the number of bytes received by the CDC interface from the device, waiting to be read. This indicates the number
+			 *  of bytes in the IN pipe bank only, and thus the number of calls to \ref CDC_Host_ReceiveByte() which are guaranteed to succeed
+			 *  immediately. If multiple bytes are to be received, they should be buffered by the user application, as the pipe bank will not be
+			 *  released back to the USB controller until all bytes are read.
 			 *
 			 *  \pre This function must only be called when the Host state machine is in the HOST_STATE_Configured state or the
 			 *       call will fail.
@@ -248,17 +251,17 @@
 			uint16_t CDC_Host_BytesReceived(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo) ATTR_NON_NULL_PTR_ARG(1);
 
 			/** Reads a byte of data from the device. If no data is waiting to be read of if a USB device is not connected, the function
-			 *  returns 0. The \ref CDC_Host_BytesReceived() function should be queried before data is received to ensure that no data
+			 *  returns a negative value. The \ref CDC_Host_BytesReceived() function may be queried in advance to determine how many bytes
-			 *  underflow occurs.
+			 *  are currently buffered in the CDC interface's data receive pipe.
 			 *
 			 *  \pre This function must only be called when the Host state machine is in the HOST_STATE_Configured state or the
 			 *       call will fail.
 			 *
 			 *  \param[in,out] CDCInterfaceInfo  Pointer to a structure containing a CDC Class host configuration and state.
 			 *
-			 *  \return Next received byte from the device, or 0 if no data received.
+			 *  \return Next received byte from the device, or a negative value if no data received.
 			 */
-			uint8_t CDC_Host_ReceiveByte(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo) ATTR_NON_NULL_PTR_ARG(1);
+			int16_t CDC_Host_ReceiveByte(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo) ATTR_NON_NULL_PTR_ARG(1);
 			
 			/** Flushes any data waiting to be sent, ensuring that the send buffer is cleared.
 			 *

LUFA/ManPages/ChangeLog.txt

@@ -41,6 +41,8 @@
   *  - Internal USB driver source files renamed and moved to ease future possible architecture ports
   *  - All internal pseudo-function macros have been converted to true inline functions for type-safety and readability
   *  - Changed LED indicator masks for the AVRISP-MKII project, so that there are defined roles for each LED
+  *  - Altered the CDC Deivice and Host Class drivers' receive byte routines, so that no data is indicated by a negative return value
+  *  - Added auto flushing of OUT data to the CDC Host Class driver's USBTask function to automatically flush the send pipe buffer
   *
   *  <b>Fixed:</b>
   *  - Fixed AVRISP project sending a LOAD EXTENDED ADDRESS command to 128KB AVRs after programming or reading from

LUFA/ManPages/MigrationInformation.txt

@@ -32,6 +32,16 @@
  *      enhanced \ref USB_Device_SendRemoteWakeup() function. Existing code may now discard any checks to USB_Device_IsRemoteWakeupSent().
  *    - The USB_Device_IsUSBSuspended() macro has been removed, as it is obsolete. Existing code should compare \ref USB_DeviceState
  *      to see if it the device is in the \ref DEVICE_STATE_Suspended state instead.
+ *    - The \ref CDC_Device_ReceiveByte() function has changed, and now returns a signed 16-bit integer, with -1 indicating no data was
+ *      received. This allows for more efficient coding, as a call to \ref CDC_Device_BytesReceived() is no longer needed if the exact
+ *      number of queued bytes received is not needed.
+ *
+ *  <b>Host Mode</b>
+ *    - The \ref CDC_Host_ReceiveByte() function has changed, and now returns a signed 16-bit integer, with -1 indicating no data was
+ *      received. This allows for more efficient coding, as a call to \ref CDC_Device_BytesReceived() is no longer needed if the exact
+ *      number of queued bytes received is not needed.
+ *    - The \ref CDC_Host_USBTask() now calls \ref CDC_Host_Flush() automatically, flushing any queued data to the attached device. Manual
+ *      flushing of the interface is no longer needed if the flushes should be in sync with calls to \ref CDC_Host_USBTask().
  *
  * \section Sec_Migration100513 Migrating from 100219 to 100513
  *

Projects/Benito/Benito.c

@@ -92,9 +92,10 @@ int main(void)
 	for (;;)
 	{
 		/* Echo bytes from the host to the target via the hardware USART */
-		if (CDC_Device_BytesReceived(&VirtualSerial_CDC_Interface) && (UCSR1A & (1 << UDRE1)))
+		int16_t ReceivedByte = CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface);
+		if (!(ReceivedByte < 0) && (UCSR1A & (1 << UDRE1)))
 		{
-			UDR1 = CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface);
+			UDR1 = ReceivedByte;
 
 			LEDs_TurnOnLEDs(LEDMASK_TX);
 			PulseMSRemaining.TxLEDPulse = TX_RX_LED_PULSE_MS;			

Projects/USBtoSerial/USBtoSerial.c

@@ -82,13 +82,9 @@ int main(void)
 	for (;;)
 	{
 		/* Read bytes from the USB OUT endpoint into the USART transmit buffer */
-		for (uint8_t DataBytesRem = CDC_Device_BytesReceived(&VirtualSerial_CDC_Interface); DataBytesRem != 0; DataBytesRem--)
+		int16_t ReceivedByte = CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface);
-		{
+		if (!(ReceivedByte < 0) && !(RingBuffer_IsFull(&USBtoUSART_Buffer)))
-			if (RingBuffer_IsFull(&USBtoUSART_Buffer))
+		  RingBuffer_AtomicInsert(&USBtoUSART_Buffer, (uint8_t)ReceivedByte);		
-			  break;
-			  
-			RingBuffer_AtomicInsert(&USBtoUSART_Buffer, CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface));
-		}
 		
 		/* Check if the software USART flush timer has expired */
 		if (TIFR0 & (1 << TOV0))

Projects/XPLAINBridge/XPLAINBridge.c

@@ -120,7 +120,8 @@ void UARTBridge_Task(void)
 	  return;
 
 	/* Read bytes from the USB OUT endpoint into the UART transmit buffer */
-	if (CDC_Device_BytesReceived(&VirtualSerial_CDC_Interface) && !(RingBuffer_IsFull(&USBtoUART_Buffer)))
+	int16_t ReceivedByte = CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface);
+	if (!(ReceivedByte < 0) && !(RingBuffer_IsFull(&USBtoUART_Buffer)))
 	  RingBuffer_AtomicInsert(&USBtoUART_Buffer, CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface));
 	
 	/* Check if the software UART flush timer has expired */