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

[pub/USBasp.git] / LUFA / Drivers / USB / Class / Device / CDC.h

diff --git a/LUFA/Drivers/USB/Class/Device/CDC.h b/LUFA/Drivers/USB/Class/Device/CDC.h
index 9e92d5f..3ada8f7 100644 (file)
--- a/LUFA/Drivers/USB/Class/Device/CDC.h
+++ b/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
-                        *  underflow occurs.
+                        *  returns a negative value. The \ref CDC_Device_BytesReceived() function may be queried in advance to determine how many
+                        *  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.
                         *