X-Git-Url: http://git.linex4red.de/pub/USBasp.git/blobdiff_plain/97143bf81480d3f642e33684349c601d5cd0b1ae..1621158c622e8dbe49deaacf88ea3f5b843b54ac:/LUFA/Drivers/USB/Class/Host/CDC.h

diff --git a/LUFA/Drivers/USB/Class/Host/CDC.h b/LUFA/Drivers/USB/Class/Host/CDC.h
index 640242819..d71c1671f 100644
--- a/LUFA/Drivers/USB/Class/Host/CDC.h
+++ b/LUFA/Drivers/USB/Class/Host/CDC.h
@@ -217,7 +217,7 @@
 			 *  \return A value from the \ref Pipe_Stream_RW_ErrorCodes_t enum.
 			 */
 			uint8_t CDC_Host_SendString(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo,
-			                            char* const Data,
+			                            const char* const Data,
 			                            const uint16_t Length) ATTR_NON_NULL_PTR_ARG(1) ATTR_NON_NULL_PTR_ARG(2);
 			
 			/** Sends a given byte to the attached USB device, if connected. If a device is not connected when the function is called, the
@@ -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
-			 *  underflow occurs.
+			 *  returns a negative value. The \ref CDC_Host_BytesReceived() function may be queried in advance to determine how many bytes
+			 *  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.
 			 *
@@ -331,7 +334,7 @@
 				static uint8_t DCOMP_CDC_Host_NextCDCControlInterface(void* const CurrentDescriptor) ATTR_NON_NULL_PTR_ARG(1);
 				static uint8_t DCOMP_CDC_Host_NextCDCDataInterface(void* const CurrentDescriptor) ATTR_NON_NULL_PTR_ARG(1);
 				static uint8_t DCOMP_CDC_Host_NextCDCInterfaceEndpoint(void* const CurrentDescriptor) ATTR_NON_NULL_PTR_ARG(1);
-			#endif	
+			#endif
 	#endif
 				
 	/* Disable C linkage for C++ Compilers: */