Altered the CDC Deivice and Host Class drivers' receive byte routines, so that no...

[pub/USBasp.git] / 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 6402428..56bcf31 100644 (file)
--- a/LUFA/Drivers/USB/Class/Host/CDC.h
+++ b/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
-                        *  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.
                         *