Detailed Description
The following files must be built with any user project that uses this module:
- LUFA/Drivers/USB/Class/Device/CDC.c
Device Mode USB Class driver framework interface, for the CDC USB Class driver.
- Note:
- There are several major drawbacks to the CDC-ACM standard USB class, however it is very standardized and thus usually available as a built-in driver on most platforms, and so is a better choice than a proprietary serial class.
One major issue with CDC-ACM is that it requires two Interface descriptors, which will upset most hosts when part of a multi-function "Composite" USB device, as each interface will be loaded into a separate driver instance. To conbat this, you should use the "Interface Association Descriptor" addendum to the USB standard which is available on most OSes when creating Composite devices.
Another major oversight is that there is no mechanism for the host to notify the device that there is a data sink on the host side ready to accept data. This means that the device may try to send data while the host isn't listening, causing lengthy blocking timeouts in the transmission routines. To combat this, it is recommended that the virtual serial line DTR (Data Terminal Ready) be used where possible to determine if a host application is ready for data.
Function Documentation
Determines the number of bytes received by the CDC interface from the host, waiting to be read.
- Note:
- This function must only be called when the Device state machine is in the DEVICE_STATE_Configured state or the call will fail.
- Parameters:
-
[in,out] | CDCInterfaceInfo | Pointer to a structure containing a CDC Class configuration and state |
- Returns:
- Total number of buffered bytes received from the host
Configures the endpoints of a given CDC interface, ready for use. This should be linked to the library EVENT_USB_Device_ConfigurationChanged() event so that the endpoints are configured when the configuration containing the given CDC interface is selected.
- Parameters:
-
[in,out] | CDCInterfaceInfo | Pointer to a structure containing a CDC Class configuration and state |
- Returns:
- Boolean true if the endpoints were successfully configured, false otherwise
Identical to CDC_Device_CreateStream(), except that reads are blocking until the calling stream function terminates the transfer. While blocking, the USB and CDC service tasks are called repeatedly to maintain USB communications.
- Parameters:
-
[in,out] | CDCInterfaceInfo | Pointer to a structure containing a CDC Class configuration and state |
[in,out] | Stream | Pointer to a FILE structure where the created stream should be placed |
Creates a standard characer stream for the given CDC Device instance so that it can be used with all the regular functions in the avr-libc <stdio.h> library that accept a FILE stream as a destination (e.g. fprintf). The created stream is bidirectional and can be used for both input and output functions.
Reading data from this stream is non-blocking, i.e. in most instances, complete strings cannot be read in by a single fetch, as the endpoint will not be ready at some point in the transmission, aborting the transfer. However, this may be used when the read data is processed byte-per-bye (via getc()) or when the user application will implement its own line buffering.
- Note:
- The created stream can be given as stdout if desired to direct the standard output from all <stdio.h> functions to the given CDC interface.
- Parameters:
-
[in,out] | CDCInterfaceInfo | Pointer to a structure containing a CDC Class configuration and state |
[in,out] | Stream | Pointer to a FILE structure where the created stream should be placed |
Flushes any data waiting to be sent, ensuring that the send buffer is cleared.
- Note:
- This function must only be called when the Device state machine is in the DEVICE_STATE_Configured state or the call will fail.
- Parameters:
-
[in,out] | CDCInterfaceInfo | Pointer to a structure containing a CDC Class configuration and state |
- Returns:
- A value from the Endpoint_WaitUntilReady_ErrorCodes_t enum
Processes incoming control requests from the host, that are directed to the given CDC class interface. This should be linked to the library EVENT_USB_Device_UnhandledControlRequest() event.
- Parameters:
-
[in,out] | CDCInterfaceInfo | Pointer to a structure containing a CDC Class configuration and state |
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 CDC_Device_BytesReceived() function should be queried before data is received to ensure that no data underflow occurs.
- Note:
- This function must only be called when the Device state machine is in the DEVICE_STATE_Configured state or the call will fail.
- Parameters:
-
[in,out] | CDCInterfaceInfo | Pointer to a structure containing a CDC Class configuration and state |
- Returns:
- Next received byte from the host, or 0 if no data received
Sends a given byte to the attached USB host, if connected. If a host is not connected when the function is called, the byte is discarded. Bytes will be queued for transmission to the host until either the endpoint bank becomes full, or the CDC_Device_Flush() function is called to flush the pending data to the host. This allows for multiple bytes to be packed into a single endpoint packet, increasing data throughput.
- Note:
- This function must only be called when the Device state machine is in the DEVICE_STATE_Configured state or the call will fail.
- Parameters:
-
[in,out] | CDCInterfaceInfo | Pointer to a structure containing a CDC Class configuration and state |
[in] | Data | Byte of data to send to the host |
- Returns:
- A value from the Endpoint_WaitUntilReady_ErrorCodes_t enum
Sends a Serial Control Line State Change notification to the host. This should be called when the virtual serial control lines (DCD, DSR, etc.) have changed states, or to give BREAK notifications to the host. Line states persist until they are cleared via a second notification. This should be called each time the CDC class driver's ControlLineStates.DeviceToHost value is updated to push the new states to the USB host.
- Note:
- This function must only be called when the Device state machine is in the DEVICE_STATE_Configured state or the call will fail.
- Parameters:
-
[in,out] | CDCInterfaceInfo | Pointer to a structure containing a CDC Class configuration and state |
Sends a given string to the attached USB host, if connected. If a host is not connected when the function is called, the string is discarded. Bytes will be queued for transmission to the host until either the endpoint bank becomes full, or the CDC_Device_Flush() function is called to flush the pending data to the host. This allows for multiple bytes to be packed into a single endpoint packet, increasing data throughput.
- Note:
- This function must only be called when the Device state machine is in the DEVICE_STATE_Configured state or the call will fail.
- Parameters:
-
[in,out] | CDCInterfaceInfo | Pointer to a structure containing a CDC Class configuration and state |
[in] | Data | Pointer to the string to send to the host |
[in] | Length | Size in bytes of the string to send to the host |
- Returns:
- A value from the Endpoint_Stream_RW_ErrorCodes_t enum
General management task for a given CDC class interface, required for the correct operation of the interface. This should be called frequently in the main program loop, before the master USB management task USB_USBTask().
- Parameters:
-
[in,out] | CDCInterfaceInfo | Pointer to a structure containing a CDC Class configuration and state |
CDC class driver event for a control line state change on a CDC interface. This event fires each time the host requests a control line state change (containing the virtual serial control line states, such as DTR) and may be hooked in the user program by declaring a handler function with the same name and parameters listed here. The new control line states are available in the ControlLineStates.HostToDevice value inside the CDC interface structure passed as a parameter, set as a mask of CDC_CONTROL_LINE_OUT_* masks.
- Parameters:
-
[in,out] | CDCInterfaceInfo | Pointer to a structure containing a CDC Class configuration and state |
CDC class driver event for a line encoding change on a CDC interface. This event fires each time the host requests a line encoding change (containing the serial parity, baud and other configuration information) and may be hooked in the user program by declaring a handler function with the same name and parameters listed here. The new line encoding settings are available in the LineEncoding structure inside the CDC interface structure passed as a parameter.
- Parameters:
-
[in,out] | CDCInterfaceInfo | Pointer to a structure containing a CDC Class configuration and state |