NIM_DSP6748/extern/usblib/device/usbdcdc.c

//*****************************************************************************
//
// usbdcdc.c - USB CDC ACM (serial) device class driver.
//
// Copyright (c) 2008-2010 Texas Instruments Incorporated.  All rights reserved.
// Software License Agreement
// 
// Texas Instruments (TI) is supplying this software for use solely and
// exclusively on TI's microcontroller products. The software is owned by
// TI and/or its suppliers, and is protected under applicable copyright
// laws. You may not combine this software with "viral" open-source
// software in order to form a larger program.
// 
// THIS SOFTWARE IS PROVIDED "AS IS" AND WITH ALL FAULTS.
// NO WARRANTIES, WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, BUT
// NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. TI SHALL NOT, UNDER ANY
// CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL, OR CONSEQUENTIAL
// DAMAGES, FOR ANY REASON WHATSOEVER.
// 
// This is part of AM1808 StarterWare USB Library and reused from revision 6288 
// of the  Stellaris USB Library.
//
//*****************************************************************************
#include "hw_usb.h"
#include "hw_types.h"
#include "debug.h"
#include "interrupt.h"
#include "usb.h"
#include "usblib.h"
#include "usbdevice.h"
#include "usbcdc.h"
#include "usbdcdc.h"
#include "usbdcomp.h"
#include "usblibpriv.h"

//*****************************************************************************
//
//! \addtogroup cdc_device_class_api
//! @{
//
//*****************************************************************************

//*****************************************************************************
//
// Some assumptions and deviations from the CDC specification
// ----------------------------------------------------------
//
// 1.  Although the CDC specification indicates that the following requests
// should be supported by ACM CDC devices, these don't seem relevant to a
// virtual COM port implementation and are never seen when connecting to a
// Windows host and running either Hyperterminal or TeraTerm.  As a result,
// this implementation does not support them and stalls endpoint 0 if they are
// received.
//          - SEND_ENCAPSULATED_COMMAND
//          - GET_ENCAPSULATED_RESPONSE
//          - SET_COMM_FEATURE
//          - GET_COMM_FEATURE
//          - CLEAR_COMM_FEATURE
//
// 2.  The CDC specification is very clear on the fact that an ACM device
// should offer two interfaces - a control interface offering an interrupt IN
// endpoint and a data interface offering bulk IN and OUT endpoints.  Using
// this descriptor configuration, however, Windows insists on enumerating the
// device as two separate entities resulting in two virtual COM ports or one
// COM port and an Unknown Device (depending upon INF contents) appearing
// in Device Manager.  This implementation, derived by experimentation and
// examination of other virtual COM and CDC solutions, uses only a single
// interface combining all three endpoints.  This appears to satisfy
// Windows2000, XP and Vista and operates as intended using the Hyperterminal
// and TeraTerm terminal emulators.  Your mileage may vary with other
// (untested) operating systems!
//
//*****************************************************************************

//*****************************************************************************
//
// The subset of endpoint status flags that we consider to be reception
// errors.  These are passed to the client via USB_EVENT_ERROR if seen.
//
//*****************************************************************************
#define USB_RX_ERROR_FLAGS      (USBERR_DEV_RX_DATA_ERROR | \
                                 USBERR_DEV_RX_OVERRUN |    \
                                 USBERR_DEV_RX_FIFO_FULL)

//*****************************************************************************
//
// Size of the buffer to hold request-specific data read from the host.  This
// must be sized to accommodate the largest request structure that we intend
// processing.
//
//*****************************************************************************
#define MAX_REQUEST_DATA_SIZE sizeof(tLineCoding)

//*****************************************************************************
//This macro is used to diable the bit band operartion. Need to undefine this macro to use the 
// bit band operation.
//***************************************************************************
#define DISABLE_BIT_BAND

//*****************************************************************************
//
// Flags that may appear in usDeferredOpFlags to indicate some operation that
// has been requested but could not be processed at the time it was received.
//
//*****************************************************************************
#define CDC_DO_SERIAL_STATE_CHANGE 0
#define CDC_DO_SEND_BREAK          1
#define CDC_DO_CLEAR_BREAK         2
#define CDC_DO_LINE_CODING_CHANGE  3
#define CDC_DO_LINE_STATE_CHANGE   4
#define CDC_DO_PACKET_RX           5

//*****************************************************************************
//
// The subset of deferred operations which result in the receive channel
// being blocked.
//
//*****************************************************************************
#define RX_BLOCK_OPS ((1 << CDC_DO_SEND_BREAK) |                              \
                      (1 << CDC_DO_LINE_CODING_CHANGE) |                      \
                      (1 << CDC_DO_LINE_STATE_CHANGE))

//*****************************************************************************
//
// Macros to convert between USB controller base address and an index.  These
// are currently trivial but are included to allow for the possibility of
// supporting more than one controller in the future.
//
//*****************************************************************************
#if (USB_NUM_INSTANCE == 2)
#define USB_BASE_TO_INDEX(BaseAddr, index) do{                   \
                                    if(USB0_BASE==BaseAddr)      \
                                        index = 0;               \
                                    else if(USB1_BASE==BaseAddr) \
                                        index = 1;               \
                                    else                         \
                                        index = -1;              \
                                   }while(0)

#define USB_INDEX_TO_BASE(Index, BaseAddr)   (                   \
                                    if(0==Index)                 \
                                        BaseAddr = USB0_BASE;    \
                                    else if(1==Index)            \
                                        BaseAddr = USB1_BASE;    \
                                    else                         \
                                        BaseAddr = -1;           \
                                   )
#else
#define USB_BASE_TO_INDEX(BaseAddr, index) do{                   \
                                    if(USB0_BASE==BaseAddr)      \
                                        index = 0;               \
                                    else                         \
                                        index = -1;              \
                                   }while(0)

#define USB_INDEX_TO_BASE(Index, BaseAddr)   (                   \
                                    if(0==Index)                 \
                                        BaseAddr = USB0_BASE;    \
                                    else                         \
                                        BaseAddr = -1;           \
                                   )
#endif

//*****************************************************************************
//
// Endpoints to use for each of the required endpoints in the driver.
//
//*****************************************************************************
#define CONTROL_ENDPOINT        USB_EP_1
#define DATA_IN_ENDPOINT        USB_EP_2
#define DATA_OUT_ENDPOINT       USB_EP_1

//*****************************************************************************
//
// The following are the USB interface numbers for the CDC serial device.
//
//*****************************************************************************
#define SERIAL_INTERFACE_CONTROL    0
#define SERIAL_INTERFACE_DATA       1

//*****************************************************************************
//
// Maximum packet size for the bulk endpoints used for serial data
// transmission and reception and the associated FIFO sizes to set aside
// for each endpoint.
//
//*****************************************************************************
#define DATA_IN_EP_FIFO_SIZE    USB_FIFO_SZ_64
#define DATA_OUT_EP_FIFO_SIZE   USB_FIFO_SZ_64
#define CTL_IN_EP_FIFO_SIZE     USB_FIFO_SZ_16

#define DATA_IN_EP_MAX_SIZE     USB_FIFO_SZ_TO_BYTES(DATA_IN_EP_FIFO_SIZE)
#define DATA_OUT_EP_MAX_SIZE    USB_FIFO_SZ_TO_BYTES(DATA_IN_EP_FIFO_SIZE)
#define CTL_IN_EP_MAX_SIZE      USB_FIFO_SZ_TO_BYTES(CTL_IN_EP_FIFO_SIZE)

//*****************************************************************************
//
// The collection of serial state flags indicating character errors.
//
//*****************************************************************************
#define USB_CDC_SERIAL_ERRORS (USB_CDC_SERIAL_STATE_OVERRUN |                 \
                               USB_CDC_SERIAL_STATE_PARITY |                  \
                               USB_CDC_SERIAL_STATE_FRAMING)


//*****************************************************************************
//
// USB instance Object
//
//*****************************************************************************
extern tUSBInstanceObject g_USBInstance[];

//*****************************************************************************
//
// Device Descriptor.  This is stored in RAM to allow several fields to be
// changed at runtime based on the client's requirements.
//
//*****************************************************************************
unsigned char g_pCDCSerDeviceDescriptor[] =
{
    18,                     // Size of this structure.
    USB_DTYPE_DEVICE,       // Type of this structure.
    USBShort(0x200),        // USB version 1.1 (if we say 2.0, hosts assume
                            // high-speed - see USB 2.0 spec 9.2.6.6)
    USB_CLASS_CDC,          // USB Device Class (spec 5.1.1)
    0,                      // USB Device Sub-class (spec 5.1.1)
    USB_CDC_PROTOCOL_NONE,  // USB Device protocol (spec 5.1.1)
    64,                     // Maximum packet size for default pipe.
    USBShort(0),            // Vendor ID (filled in during USBDCDCInit).
    USBShort(0),            // Product ID (filled in during USBDCDCInit).
    USBShort(0x100),        // Device Version BCD.
    1,                      // Manufacturer string identifier.
    2,                      // Product string identifier.
    3,                      // Product serial number.
    1                       // Number of configurations.
};

//*****************************************************************************
//
// CDC Serial configuration descriptor.
//
// It is vital that the configuration descriptor bConfigurationValue field
// (byte 6) is 1 for the first configuration and increments by 1 for each
// additional configuration defined here.  This relationship is assumed in the
// device stack for simplicity even though the USB 2.0 specification imposes
// no such restriction on the bConfigurationValue values.
//
// Note that this structure is deliberately located in RAM since we need to
// be able to patch some values in it based on client requirements.
//
//*****************************************************************************
unsigned char g_pCDCSerDescriptor[] =
{
    //
    // Configuration descriptor header.
    //
    9,                          // Size of the configuration descriptor.
    USB_DTYPE_CONFIGURATION,    // Type of this descriptor.
    USBShort(9),                // The total size of this full structure, this
                                // will be patched so it is just set to the
                                // size of this structure.
    2,                          // The number of interfaces in this
                                // configuration.
    1,                          // The unique value for this configuration.
    5,                          // The string identifier that describes this
                                // configuration.
    USB_CONF_ATTR_SELF_PWR,     // Bus Powered, Self Powered, remote wake up.
    250,                        // The maximum power in 2mA increments.
};

const tConfigSection g_sCDCSerConfigSection =
{
    sizeof(g_pCDCSerDescriptor),
    g_pCDCSerDescriptor
};

//*****************************************************************************
//
// This is the Interface Association Descriptor for the serial device used in
// composite devices.
//
//*****************************************************************************
unsigned char g_pIADSerDescriptor[] =
{

    8,                          // Size of the interface descriptor.
    USB_DTYPE_INTERFACE_ASC,    // Interface Association Type.
    0x0,                        // Default starting interface is 0.
    0x2,                        // Number of interfaces in this association.
    USB_CLASS_CDC,              // The device class for this association.
    USB_CDC_SUBCLASS_ABSTRACT_MODEL, // The device subclass for this
                                     // association.
    USB_CDC_PROTOCOL_V25TER,    // The protocol for this association.
    0                           // The string index for this association.
};

const tConfigSection g_sIADSerConfigSection =
{
    sizeof(g_pIADSerDescriptor),
    g_pIADSerDescriptor
};

//*****************************************************************************
//
// This is the control interface for the serial device.
//
//*****************************************************************************
const unsigned char g_pCDCSerCommInterface[] =
{
    //
    // Communication Class Interface Descriptor.
    //
    9,                          // Size of the interface descriptor.
    USB_DTYPE_INTERFACE,        // Type of this descriptor.
    SERIAL_INTERFACE_CONTROL,   // The index for this interface.
    0,                          // The alternate setting for this interface.
    1,                          // The number of endpoints used by this
                                // interface.
    USB_CLASS_CDC,              // The interface class constant defined by
                                // USB-IF (spec 5.1.3).
    USB_CDC_SUBCLASS_ABSTRACT_MODEL,    // The interface sub-class constant
                                        // defined by USB-IF (spec 5.1.3).
    USB_CDC_PROTOCOL_V25TER,    // The interface protocol for the sub-class
                                // specified above.
    4,                          // The string index for this interface.

    //
    // Communication Class Interface Functional Descriptor - Header
    //
    5,                          // Size of the functional descriptor.
    USB_CDC_CS_INTERFACE,       // CDC interface descriptor
    USB_CDC_FD_SUBTYPE_HEADER,  // Header functional descriptor
    USBShort(0x110),            // Complies with CDC version 1.1

    //
    // Communication Class Interface Functional Descriptor - ACM
    //
    4,                          // Size of the functional descriptor.
    USB_CDC_CS_INTERFACE,       // CDC interface descriptor
    USB_CDC_FD_SUBTYPE_ABSTRACT_CTL_MGMT,
    USB_CDC_ACM_SUPPORTS_LINE_PARAMS | USB_CDC_ACM_SUPPORTS_SEND_BREAK,

    //
    // Communication Class Interface Functional Descriptor - Unions
    //
    5,                          // Size of the functional descriptor.
    USB_CDC_CS_INTERFACE,       // CDC interface descriptor
    USB_CDC_FD_SUBTYPE_UNION,
    SERIAL_INTERFACE_CONTROL,
    SERIAL_INTERFACE_DATA,      // Data interface number

    //
    // Communication Class Interface Functional Descriptor - Call Management
    //
    5,                          // Size of the functional descriptor.
    USB_CDC_CS_INTERFACE,       // CDC interface descriptor
    USB_CDC_FD_SUBTYPE_CALL_MGMT,
    USB_CDC_CALL_MGMT_HANDLED,
    SERIAL_INTERFACE_DATA,      // Data interface number

    //
    // Endpoint Descriptor (interrupt, IN)
    //
    7,                              // The size of the endpoint descriptor.
    USB_DTYPE_ENDPOINT,             // Descriptor type is an endpoint.
    USB_EP_DESC_IN | USB_EP_TO_INDEX(CONTROL_ENDPOINT),
    USB_EP_ATTR_INT,                // Endpoint is an interrupt endpoint.
    USBShort(CTL_IN_EP_MAX_SIZE),   // The maximum packet size.
    10                             // The polling interval for this endpoint.
};

const tConfigSection g_sCDCSerCommInterfaceSection =
{
    sizeof(g_pCDCSerCommInterface),
    g_pCDCSerCommInterface
};

//*****************************************************************************
//
// This is the Data interface for the serial device.
//
//*****************************************************************************
const unsigned char g_pCDCSerDataInterface[] =
{
    //
    // Communication Class Data Interface Descriptor.
    //
    9,                          // Size of the interface descriptor.
    USB_DTYPE_INTERFACE,        // Type of this descriptor.
    SERIAL_INTERFACE_DATA,      // The index for this interface.
    0,                          // The alternate setting for this interface.
    2,                          // The number of endpoints used by this
                                // interface.
    USB_CLASS_CDC_DATA,         // The interface class constant defined by
                                // USB-IF (spec 5.1.3).
    0,                          // The interface sub-class constant
                                // defined by USB-IF (spec 5.1.3).
    USB_CDC_PROTOCOL_NONE,      // The interface protocol for the sub-class
                                // specified above.
    0,                          // The string index for this interface.

    //
    // Endpoint Descriptor
    //
    7,                              // The size of the endpoint descriptor.
    USB_DTYPE_ENDPOINT,             // Descriptor type is an endpoint.
    USB_EP_DESC_IN | USB_EP_TO_INDEX(DATA_IN_ENDPOINT),
    USB_EP_ATTR_BULK,               // Endpoint is a bulk endpoint.
    USBShort(DATA_IN_EP_MAX_SIZE),  // The maximum packet size.
    0,                              // The polling interval for this endpoint.

    //
    // Endpoint Descriptor
    //
    7,                              // The size of the endpoint descriptor.
    USB_DTYPE_ENDPOINT,             // Descriptor type is an endpoint.
    USB_EP_DESC_OUT | USB_EP_TO_INDEX(DATA_OUT_ENDPOINT),
    USB_EP_ATTR_BULK,               // Endpoint is a bulk endpoint.
    USBShort(DATA_OUT_EP_MAX_SIZE), // The maximum packet size.
    0,                              // The polling interval for this endpoint.
};

const tConfigSection g_sCDCSerDataInterfaceSection =
{
    sizeof(g_pCDCSerDataInterface),
    g_pCDCSerDataInterface
};

//*****************************************************************************
//
// This array lists all the sections that must be concatenated to make a
// single, complete CDC ACM configuration descriptor.
//
//*****************************************************************************
const tConfigSection *g_psCDCSerSections[] =
{
    &g_sCDCSerConfigSection,
    &g_sCDCSerCommInterfaceSection,
    &g_sCDCSerDataInterfaceSection,
};

#define NUM_CDCSER_SECTIONS (sizeof(g_psCDCSerSections) /                     \
                             sizeof(tConfigSection *))

//*****************************************************************************
//
// The header for the single configuration.  This is the root of the data
// structure that defines all the bits and pieces that are pulled together to
// generate the configuration descriptor.
//
//*****************************************************************************
const tConfigHeader g_sCDCSerConfigHeader =
{
    NUM_CDCSER_SECTIONS,
    g_psCDCSerSections
};

//*****************************************************************************
//
// This array lists all the sections that must be concatenated to make a
// single, complete CDC ACM configuration descriptor used in composite devices.
// The only addition is the g_sIADSerConfigSection.
//
//*****************************************************************************
const tConfigSection *g_psCDCCompSerSections[] =
{
    &g_sCDCSerConfigSection,
    &g_sIADSerConfigSection,
    &g_sCDCSerCommInterfaceSection,
    &g_sCDCSerDataInterfaceSection,
};

#define NUM_COMP_CDCSER_SECTIONS (sizeof(g_psCDCCompSerSections) /                     \
                                  sizeof(tConfigSection *))

//*****************************************************************************
//
// The header for the composite configuration.  This is the root of the data
// structure that defines all the bits and pieces that are pulled together to
// generate the configuration descriptor.
//
//*****************************************************************************
const tConfigHeader g_sCDCCompSerConfigHeader =
{
    NUM_COMP_CDCSER_SECTIONS,
    g_psCDCCompSerSections
};

//*****************************************************************************
//
// Configuration Descriptor for the CDC serial class device.
//
//*****************************************************************************
const tConfigHeader * const g_pCDCSerConfigDescriptors[] =
{
    &g_sCDCSerConfigHeader
};

//*****************************************************************************
//
// Configuration Descriptor for the CDC serial class device used in a composite
// device.
//
//*****************************************************************************
const tConfigHeader * const g_pCDCCompSerConfigDescriptors[] =
{
    &g_sCDCCompSerConfigHeader
};

//*****************************************************************************
//
// Forward references for device handler callbacks
//
//*****************************************************************************
static void HandleRequests(void *pvInstance, tUSBRequest *pUSBRequest, 
                                                        unsigned int ulIndex);
static void HandleConfigChange(void *pvInstance, unsigned int ulInfo, 
                                                        unsigned int ulIndex);
static void HandleEP0Data(void *pvInstance, unsigned int ulDataSize,  
                                                        unsigned int ulIndex);
static void HandleDisconnect(void *pvInstance);
static void HandleEndpoints(void *pvInstance, unsigned int ulStatus, 
                                                        unsigned int ulIndex);
static void HandleSuspend(void *pvInstance);
static void HandleResume(void *pvInstance);
static void HandleDevice(void *pvInstance, unsigned int ulRequest,
                         void *pvRequestData);

//*****************************************************************************
//
// The device information structure for the USB serial device.
//
//*****************************************************************************
tDeviceInfo g_sCDCSerDeviceInfo =
{
    //
    // Device event handler callbacks.
    //
    {
        //
        // GetDescriptor
        //
        0,

        //
        // RequestHandler
        //
        HandleRequests,

        //
        // InterfaceChange
        //
        0,

        //
        // ConfigChange
        //
        HandleConfigChange,

        //
        // DataReceived
        //
        HandleEP0Data,

        //
        // DataSentCallback
        //
        0,

        //
        // ResetHandler
        //
        0,

        //
        // SuspendHandler
        //
        HandleSuspend,

        //
        // ResumeHandler
        //
        HandleResume,

        //
        // DisconnectHandler
        //
        HandleDisconnect,

        //
        // EndpointHandler
        //
        HandleEndpoints,

        //
        // Device handler.
        //
        HandleDevice
    },

    //
    // The common device descriptor.
    //
    g_pCDCSerDeviceDescriptor,

    //
    // Default to no interrupt endpoint.
    //
    g_pCDCCompSerConfigDescriptors,

    //
    // String descriptors will be passed in.
    //
    0,
    0,

    //
    // Use the default USB FIFO configuration.
    //
    &g_sUSBDefaultFIFOConfig,

    //
    // Zero out the instance pointer by default.
    //
    0
};

//*****************************************************************************
//
// Set or clear deferred operation flags in an "atomic" manner.
//
// \param pusDeferredOp points to the flags variable which is to be modified.
// \param usBit indicates which bit number is to be set or cleared.
// \param bSet indicates the state that the flag must be set to.  If \b true,
// the flag is set, if \b false, the flag is cleared.
//
// This function safely sets or clears a bit in a flag variable.  The operation
// makes use of bitbanding to ensure that the operation is atomic (no read-
// modify-write is required).
//
// \return None.
//
//*****************************************************************************
static void
SetDeferredOpFlag(volatile unsigned short *pusDeferredOp,
                  unsigned short usBit, tBoolean bSet)
{
#ifdef DISABLE_BIT_BAND
    if(bSet)
    {
        HWREG(pusDeferredOp) |= (1<<usBit);
    }
    else
    {
        HWREG(pusDeferredOp) &= ~(1<<usBit);
    }
#else
    //
    // Set the flag bit to 1 or 0 using a bitband access.
    //

    HWREGBITH(pusDeferredOp, usBit) = bSet ? 1 : 0;
#endif
}

//*****************************************************************************
//
// Determines whether or not a client has consumed all received data previously
// passed to it.
//
//! \param psDevice is the pointer to the device instance structure as returned
//! by USBDCDCInit().
//
// This function is called to determine whether or not a device has consumed
// all data previously passed to it via its receive callback.
//
// \return Returns \b true on success or \b false on failure.
//
//*****************************************************************************
static tBoolean
DeviceConsumedAllData(const tUSBDCDCDevice *psDevice)
{
    unsigned int ulRemaining;

    //
    // Send the device an event requesting that it tell us how many bytes
    // of data it still has to process.
    //
    ulRemaining = psDevice->pfnRxCallback(psDevice->pvRxCBData,
    USB_EVENT_DATA_REMAINING, 0, (void *)0);

    //
    // If any data remains to be processed, return false, else return true.
    //
    return (ulRemaining ? false : true);
}

//*****************************************************************************
//
// Notifies the client that it should set or clear a break condition.
//
// \param psDevice is the pointer to the device instance structure as returned
// by USBDCDCInit().
// \param bSend is \b true if a break condition is to be set or \b false if
// it is to be cleared.
//
// This function is called to instruct the client to start or stop sending a
// break condition on its serial transmit line.
//
// \return Returns \b true on success or \b false on failure.
//
//*****************************************************************************
static void
SendBreak(const tUSBDCDCDevice *psDevice, tBoolean bSend)
{
    tCDCSerInstance *psInst;

    //
    // Get our instance data pointer.
    //
    psInst = psDevice->psPrivateCDCSerData;

    //
    // Set the break state flags as necessary.  If we are turning the break on,
    // set the flag to tell ourselves that we need to notify the client when
    // it is time to turn it off again.
    //
    SetDeferredOpFlag(&psInst->usDeferredOpFlags, CDC_DO_SEND_BREAK, false);
    SetDeferredOpFlag(&psInst->usDeferredOpFlags, CDC_DO_CLEAR_BREAK, bSend);

    //
    // Tell the client to start or stop sending the break.
    //
    psDevice->pfnControlCallback(psDevice->pvControlCBData,
                                 (bSend ? USBD_CDC_EVENT_SEND_BREAK :
                                          USBD_CDC_EVENT_CLEAR_BREAK), 0,
                                 (void *)0);
}

//*****************************************************************************
//
// Notifies the client of a host request to set the serial communication
// parameters.
//
// \param psDevice is the device instance whose communication parameters are to
// be set.
//
// This function is called to notify the client when the host requests a change
// in the serial communication parameters (baud rate, parity, number of bits
// per character and number of stop bits) to use.
//
// \return None.
//
//*****************************************************************************
static void
SendLineCodingChange(const tUSBDCDCDevice *psDevice)
{
    tCDCSerInstance *psInst;

    //
    // Get our instance data pointer.
    //
    psInst = psDevice->psPrivateCDCSerData;

    //
    // Clear the flag we use to tell ourselves that the line coding change has
    // yet to be notified to the client.
    //
    SetDeferredOpFlag(&psInst->usDeferredOpFlags, CDC_DO_LINE_CODING_CHANGE,
                      false);

    //
    // Tell the client to update their serial line coding parameters.
    //
    psDevice->pfnControlCallback(psDevice->pvControlCBData,
                                 USBD_CDC_EVENT_SET_LINE_CODING, 0,
                                 &(psInst->sLineCoding));
}

//*****************************************************************************
//
// Notifies the client of a host request to set the RTS and DTR handshake line
// states.
//
// \param psDevice is the device instance whose break condition is to be set or
// cleared.
//
// This function is called to notify the client when the host requests a change
// in the state of one or other of the RTS and DTR handshake lines.
//
// \return None.
//
//*****************************************************************************
static void
SendLineStateChange(const tUSBDCDCDevice *psDevice)
{
    tCDCSerInstance *psInst;

    //
    // Get our instance data pointer.
    //
    psInst = psDevice->psPrivateCDCSerData;

    //
    // Clear the flag we use to tell ourselves that the line coding change has
    // yet to be notified to the client.
    //
    SetDeferredOpFlag(&psInst->usDeferredOpFlags, CDC_DO_LINE_STATE_CHANGE,
                      false);

    //
    // Tell the client to update their serial line coding parameters.
    //
    psDevice->pfnControlCallback(psDevice->pvControlCBData,
                                 USBD_CDC_EVENT_SET_CONTROL_LINE_STATE,
                                 psInst->usControlLineState,
                                 (void *)0);
}

//*****************************************************************************
//
// Notifies the client of a break request if no data remains to be processed.
//
// \param psDevice is the device instance that is to be commanded to send a
// break condition.
//
// This function is called when the host requests that the device set a break
// condition on the serial transmit line.  If no data received from the host
// remains to be processed, the break request is passed to the control
// callback.  If data is outstanding, the call is ignored (with the operation
// being retried on the next timer tick).
//
// \return Returns \b true if the break notification was sent, \b false
// otherwise.
//
//*****************************************************************************
static tBoolean
CheckAndSendBreak(const tUSBDCDCDevice *psDevice, unsigned short usDuration)
{
    tBoolean bCanSend;

    //
    // Has the client consumed all data received from the host yet?
    //
    bCanSend = DeviceConsumedAllData(psDevice);

    //
    // Can we send the break request?
    //
    if(bCanSend)
    {
        //
        // Pass the break request on to the client since no data remains to be
        // consumed.
        //
        SendBreak(psDevice, (usDuration ? true : false));
    }

    //
    // Tell the caller whether or not we sent the notification.
    //
    return (bCanSend);
}

//*****************************************************************************
//
// Notifies the client of a request to change the serial line parameters if no
// data remains to be processed.
//
// \param psDevice is the device instance whose line coding parameters are to
// be changed.
//
// This function is called when the host requests that the device change the
// serial line coding parameters.  If no data received from the host remains
// to be processed, the request is passed to the control callback.  If data is
// outstanding, the call is ignored (with the operation being retried on the
// next timer tick).
//
// \return Returns \b true if the notification was sent, \b false otherwise.
//
//*****************************************************************************
static tBoolean
CheckAndSendLineCodingChange(const tUSBDCDCDevice *psDevice)
{
    tBoolean bCanSend;

    //
    // Has the client consumed all data received from the host yet?
    //
    bCanSend = DeviceConsumedAllData(psDevice);

    //
    // Can we send the break request?
    //
    if(bCanSend)
    {
        //
        // Pass the request on to the client since no data remains to be
        // consumed.
        //
        SendLineCodingChange(psDevice);
    }

    //
    // Tell the caller whether or not we sent the notification.
    //
    return (bCanSend);
}

//*****************************************************************************
//
// Notifies the client of a request to change the handshake line states if no
// data remains to be processed.
//
// \param psDevice is the device instance whose handshake line states are to
// be changed.
//
// This function is called when the host requests that the device change the
// state of one or other of the RTS or DTR handshake lines.  If no data
// received from the host remains to be processed, the request is passed to
// the control callback.  If data is outstanding, the call is ignored (with
// the operation being retried on the next timer tick).
//
// \return Returns \b true if the notification was sent, \b false otherwise.
//
//*****************************************************************************
static tBoolean
CheckAndSendLineStateChange(const tUSBDCDCDevice *psDevice)
{
    tBoolean bCanSend;

    //
    // Has the client consumed all data received from the host yet?
    //
    bCanSend = DeviceConsumedAllData(psDevice);

    //
    // Can we send the break request?
    //
    if(bCanSend)
    {
        //
        // Pass the request on to the client since no data remains to be
        // consumed.
        //
        SendLineStateChange(psDevice);
    }

    //
    // Tell the caller whether or not we sent the notification.
    //
    return (bCanSend);
}

//*****************************************************************************
//
// Notifies the client of a change in the serial line state.
//
// \param psInst is the instance whose serial state is to be reported.
//
// This function is called to send the current serial state information to
// the host via the the interrupt IN endpoint.  This notification informs the
// host of problems or conditions such as parity errors, breaks received,
// framing errors, etc.
//
// \return Returns \b true on success or \b false on failure.
//
//*****************************************************************************
static tBoolean
SendSerialState(const tUSBDCDCDevice *psDevice)
{
    tUSBRequest sRequest;
    unsigned short usSerialState;
    tCDCSerInstance *psInst;
    int iRetcode;

    //
    // Get a pointer to our instance data.
    //
    psInst = psDevice->psPrivateCDCSerData;

    //
    // Remember that we are in the middle of sending a notification.
    //
    psInst->eCDCInterruptState = CDC_STATE_WAIT_DATA;

    //
    // Clear the flag we use to indicate that a send is required.
    //
    SetDeferredOpFlag(&psInst->usDeferredOpFlags, CDC_DO_SERIAL_STATE_CHANGE,
                      false);
    //
    // Take a snapshot of the serial state.
    //
    usSerialState = psInst->usSerialState;

    //
    // Build the request we will use to send the notification.
    //
    sRequest.bmRequestType = (USB_RTYPE_DIR_IN | USB_RTYPE_CLASS |
    USB_RTYPE_INTERFACE);
    sRequest.bRequest = USB_CDC_NOTIFY_SERIAL_STATE;
    sRequest.wValue = 0;
    sRequest.wIndex = 0;
    sRequest.wLength = USB_CDC_NOTIFY_SERIAL_STATE_SIZE;

    //
    // Write the request structure to the USB FIFO.
    //
    iRetcode = USBEndpointDataPut(psInst->ulUSBBase, psInst->ucControlEndpoint,
                                  (unsigned char *)&sRequest,
                                  sizeof(tUSBRequest));
    iRetcode = USBEndpointDataPut(psInst->ulUSBBase, psInst->ucControlEndpoint,
                                  (unsigned char *)&usSerialState,
                                  USB_CDC_NOTIFY_SERIAL_STATE_SIZE);

    //
    // Did we correctly write the data to the endpoint FIFO?
    //
    if(iRetcode != -1)
    {
        //
        // We put the data into the FIFO so now schedule it to be
        // sent.
        //
        iRetcode = USBEndpointDataSend(psInst->ulUSBBase,
                                       psInst->ucControlEndpoint,
                                       USB_TRANS_IN);
    }

    //
    // If an error occurred, mark the endpoint as idle (to prevent possible
    // lockup) and return an error.
    //
    if(iRetcode == -1)
    {
        psInst->eCDCInterruptState = CDC_STATE_IDLE;
        return (false);
    }
    else
    {
        //
        // Everything went fine.  Clear the error bits that we just notified
        // and return true.
        //
        psInst->usSerialState &= ~(usSerialState & USB_CDC_SERIAL_ERRORS);
        return (true);
    }
}

//*****************************************************************************
//
// Receives notifications related to data received from the host.
//
// \param psDevice is the device instance whose endpoint is to be processed.
// \param ulStatus is the USB interrupt status that caused this function to
// be called.
//
// This function is called from HandleEndpoints for all interrupts signaling
// the arrival of data on the bulk OUT endpoint (in other words, whenever the
// host has sent us a packet of data).  We inform the client that a packet
// is available and, on return, check to see if the packet has been read.  If
// not, we schedule another notification to the client for a later time.
//
// \return Returns \b true on success or \b false on failure.
//
//*****************************************************************************
tBoolean
ProcessDataFromHost(const tUSBDCDCDevice *psDevice, unsigned int ulStatus, 
                                                            unsigned int ulIndex)
{
    unsigned int ulEPStatus;
    unsigned int ulSize;
    tCDCSerInstance *psInst;

    //
    // Get a pointer to our instance data.
    //
    psInst = psDevice->psPrivateCDCSerData;

    //
    // Get the endpoint status to see why we were called.
    //
    ulEPStatus = USBEndpointStatus(psInst->ulUSBBase,
                                   psInst->ucBulkOUTEndpoint);

    //
    // Clear the status bits.
    //
    USBDevEndpointStatusClear(psInst->ulUSBBase, psInst->ucBulkOUTEndpoint,
                              ulEPStatus);

    //
    // Has a packet been received?
    //
    if(ulEPStatus & USB_DEV_RX_PKT_RDY)
    {
        //
        // Set the flag we use to indicate that a packet read is pending.  This
        // will be cleared if the packet is read.  If the client doesn't read
        // the packet in the context of the USB_EVENT_RX_AVAILABLE callback,
        // the event will be notified later during tick processing.
        //
        SetDeferredOpFlag(&psInst->usDeferredOpFlags, CDC_DO_PACKET_RX, true);

        //
        // Is the receive channel currently blocked?
        //
        if(!psInst->bControlBlocked && !psInst->bRxBlocked)
        {
            //
            // How big is the packet we've just been sent?
            //
            ulSize = USBEndpointDataAvail(psInst->ulUSBBase,
                                          psInst->ucBulkOUTEndpoint);

            //
            // The receive channel is not blocked so let the caller know
            // that a packet is waiting.  The parameters are set to indicate
            // that the packet has not been read from the hardware FIFO yet.
            //
            psDevice->pfnRxCallback(psDevice->pvRxCBData,
                                    USB_EVENT_RX_AVAILABLE, ulSize,
                                    (void *)0);
        }

    
    }
    else
    {
        //
        // No packet was received.  Some error must have been reported.  Check
        // and pass this on to the client if necessary.
        //
        if(ulEPStatus & USB_RX_ERROR_FLAGS)
        {
            //
            // This is an error we report to the client so...
            //
            psDevice->pfnRxCallback(psDevice->pvRxCBData,
                                    USB_EVENT_ERROR,
                                    (ulEPStatus & USB_RX_ERROR_FLAGS),
                                    (void *)0);
        }

        return (false);
    }

    return (true);
}

//*****************************************************************************
//
// Receives notifications related to interrupt messages sent to the host.
//
// \param psDevice is the device instance whose endpoint is to be processed.
// \param ulStatus is the USB interrupt status that caused this function to
// be called.
//
// This function is called from HandleEndpoints for all interrupts originating
// from the interrupt IN endpoint (in other words, whenever a notification has
// been transmitted to the USB host).
//
// \return Returns \b true on success or \b false on failure.
//
//*****************************************************************************
tBoolean
ProcessNotificationToHost(const tUSBDCDCDevice *psDevice,
                          unsigned int ulStatus)
{
    unsigned int ulEPStatus;
    tCDCSerInstance *psInst;
    tBoolean bRetcode;

    //
    // Assume all will go well until we have reason to believe otherwise.
    //
    bRetcode = true;

    //
    // Get a pointer to our instance data.
    //
    psInst = psDevice->psPrivateCDCSerData;

    //
    // Get the endpoint status to see why we were called.
    //
    ulEPStatus = USBEndpointStatus(psInst->ulUSBBase,
                                   psInst->ucControlEndpoint);

    //
    // Clear the status bits.
    //
    USBDevEndpointStatusClear(psInst->ulUSBBase,
                              psInst->ucControlEndpoint, ulEPStatus);

    //
    // Did the state change while we were waiting for the previous notification
    // to complete?
    //
    if(psInst->usDeferredOpFlags & (1 << CDC_DO_SERIAL_STATE_CHANGE))
    {
        //
        // The state changed while we were waiting so we need to schedule
        // another notification immediately.
        //
        bRetcode = SendSerialState(psDevice);
    }
    else
    {
        //
        // Our last notification completed and we didn't have any new
        // notifications to make so the interrupt channel is now idle again.
        //
        psInst->eCDCInterruptState = CDC_STATE_IDLE;
    }

    //
    // Tell the caller how things went.
    //
    return (bRetcode);
}

//*****************************************************************************
//
// Receives notifications related to data sent to the host.
//
// \param psDevice is the device instance whose endpoint is to be processed.
// \param ulStatus is the USB interrupt status that caused this function to
// be called.
//
// This function is called from HandleEndpoints for all interrupts originating
// from the bulk IN endpoint (in other words, whenever data has been
// transmitted to the USB host).  We examine the cause of the interrupt and,
// if due to completion of a transmission, notify the client.
//
// \return Returns \b true on success or \b false on failure.
//
//*****************************************************************************
tBoolean
ProcessDataToHost(const tUSBDCDCDevice *psDevice, unsigned int ulStatus,
                                                            unsigned int ulIndex)
{
    tCDCSerInstance *psInst;
    unsigned int ulEPStatus, ulSize;

    //
    // Get a pointer to our instance data.
    //
    psInst = psDevice->psPrivateCDCSerData;

    //
    // Get the endpoint status to see why we were called.
    //
    ulEPStatus = USBEndpointStatus(psInst->ulUSBBase,
                                   psInst->ucBulkINEndpoint);

    //
    // Clear the status bits.
    //
    USBDevEndpointStatusClear(psInst->ulUSBBase,
                              psInst->ucBulkINEndpoint, ulEPStatus);

    //
    // Our last transmission completed.  Clear our state back to idle and
    // see if we need to send any more data.
    //
    psInst->eCDCTxState = CDC_STATE_IDLE;

    //
    // Notify the client that the last transmission completed.
    //
    ulSize = (unsigned int)psInst->usLastTxSize;
    psInst->usLastTxSize = 0;
    psDevice->pfnTxCallback(psDevice->pvTxCBData, USB_EVENT_TX_COMPLETE,
                            ulSize, (void *)0);

    return (true);
}

//*****************************************************************************
//
// Called by the USB stack for any activity involving one of our endpoints
// other than EP0.  This function is a fan out that merely directs the call to
// the correct handler depending upon the endpoint and transaction direction
// signaled in ulStatus.
//
//*****************************************************************************
static void
HandleEndpoints(void *pvInstance, unsigned int ulStatus, unsigned int ulIndex)
{
    const tUSBDCDCDevice *psDeviceInst;
    tCDCSerInstance *psInst;

    ASSERT(pvInstance != 0);

    //
    // Determine if the serial device is in single or composite mode because
    // the meaning of ulIndex is different in both cases.
    //
    psDeviceInst = pvInstance;
    psInst = psDeviceInst->psPrivateCDCSerData;

    //
    // Handler for the interrupt IN notification endpoint.
    //
    if(ulStatus & (1 << USB_EP_TO_INDEX(psInst->ucControlEndpoint)))
    {
        //
        // We have sent an interrupt notification to the host.
        //
        ProcessNotificationToHost(psDeviceInst, ulStatus);
    }

    //
    // Handler for the bulk OUT data endpoint.
    //
    if(ulStatus & (0x10000 << USB_EP_TO_INDEX(psInst->ucBulkOUTEndpoint)))
    {
        //
        // Data is being sent to us from the host.
        //
        ProcessDataFromHost(psDeviceInst, ulStatus, ulIndex);
    }

    //
    // Handler for the bulk IN data endpoint.
    //
    if(ulStatus & (1 << USB_EP_TO_INDEX(psInst->ucBulkINEndpoint)))
    {
        ProcessDataToHost(psDeviceInst, ulStatus, ulIndex);
    }
}

//*****************************************************************************
//
// Called by the USB stack whenever a configuration change occurs.
//
//*****************************************************************************
static void
HandleConfigChange(void *pvInstance, unsigned int ulInfo, unsigned int ulIndex)
{
    tCDCSerInstance *psInst;
    const tUSBDCDCDevice *psDevice;

    ASSERT(pvInstance != 0);

    //
    // Create a device instance pointer.
    //
    psDevice = (const tUSBDCDCDevice *)pvInstance;

    //
    // Get a pointer to our instance data.
    //
    psInst = psDevice->psPrivateCDCSerData;

    //
    // Set all our endpoints to idle state.
    //
    psInst->eCDCInterruptState = CDC_STATE_IDLE;
    psInst->eCDCRequestState = CDC_STATE_IDLE;
    psInst->eCDCRxState = CDC_STATE_IDLE;
    psInst->eCDCTxState = CDC_STATE_IDLE;

    //
    // If we are not currently connected so let the client know we are open
    // for business.
    //
    if(!psInst->bConnected)
    {
        //
        // Pass the connected event to the client.
        //
        psDevice->pfnControlCallback(psDevice->pvControlCBData,
                                     USB_EVENT_CONNECTED, 0, (void *)0);
    }

    //
    // Remember that we are connected.
    //
    psInst->bConnected = true;
}

//*****************************************************************************
//
// USB data received callback.
//
// This function is called by the USB stack whenever any data requested from
// EP0 is received.
//
//*****************************************************************************
static void
HandleEP0Data(void *pvInstance, unsigned int ulDataSize, unsigned int ulIndex)
{
    const tUSBDCDCDevice *psDevice;
    tCDCSerInstance *psInst;
    tBoolean bRetcode;

    ASSERT(pvInstance != 0);

    //
    // Create a device instance pointer.
    //
    psDevice = (const tUSBDCDCDevice *)pvInstance;

    //
    // If we were not passed any data, just return.
    //
    if(ulDataSize == 0)
    {
        return;
    }

    //
    // Get our instance data pointer.
    //
    psInst = psDevice->psPrivateCDCSerData;

    //
    // Make sure we are actually expecting something.
    //
    if(psInst->eCDCRequestState != CDC_STATE_WAIT_DATA)
    {
        return;
    }

    //
    // Process the data received.  This will be a request-specific data
    // block associated with the last request received.
    //
    switch (psInst->ucPendingRequest)
    {
        //
        // We just got the line coding structure.  Make sure the client has
        // read all outstanding data then pass it back to initiate a change
        // in the line state.
        //
        case USB_CDC_SET_LINE_CODING:
        {
            if(ulDataSize != sizeof(tLineCoding))
            {
                USBDCDStallEP0(ulIndex);
            }
            else
            {
                //
                // Set the flag telling us that we need to send a line coding
                // notification to the client.
                //
                SetDeferredOpFlag(&psInst->usDeferredOpFlags,
                                  CDC_DO_LINE_CODING_CHANGE, true);

                //
                // See if we can send the notification immediately.
                //
                bRetcode = CheckAndSendLineCodingChange(psDevice);

                //
                // If we couldn't send the line coding change request to the
                // client, block reception of more data from the host until
                // previous data is processed and we send the change request.
                //
                if(!bRetcode)
                {
                    psInst->bRxBlocked = true;
                }
            }
            break;
        }

            //
            // Oops - we seem to be waiting on a request which has not yet been
            // coded here.  Flag the error and stall EP0 anyway (even though
            // this would indicate a coding error).
            //
        default:
        {
            USBDCDStallEP0(ulIndex);ASSERT(ulIndex);
            break;
        }
    }

    //
    // All is well.  Set the state back to IDLE.
    //
    psInst->eCDCRequestState = CDC_STATE_IDLE;
}

//*****************************************************************************
//
// Device instance specific handler.
//
//*****************************************************************************
static void
HandleDevice(void *pvInstance, unsigned int ulRequest, void *pvRequestData)
{
    tCDCSerInstance *psInst;
    unsigned char *pucData;

    //
    // Create the serial instance data.
    //
    psInst = ((tUSBDCDCDevice *)pvInstance)->psPrivateCDCSerData;

    //
    // Create the char array used by the events supported by the USB CDC
    // serial class.
    //
    pucData = (unsigned char *)pvRequestData;

    switch(ulRequest)
    {
        //
        // This was an interface change event.
        //
        case USB_EVENT_COMP_IFACE_CHANGE:
        {
            //
            // Save the change to the appropriate interface number.
            //
            if(pucData[0] == SERIAL_INTERFACE_CONTROL)
            {
                psInst->ucInterfaceControl = pucData[1];
            }
            else if(pucData[0] == SERIAL_INTERFACE_DATA)
            {
                psInst->ucInterfaceData = pucData[1];
            }
            break;
        }

        //
        // This was an endpoint change event.
        //
        case USB_EVENT_COMP_EP_CHANGE:
        {
            //
            // Determine if this is an IN or OUT endpoint that has changed.
            //
            if(pucData[0] & USB_EP_DESC_IN)
            {
                //
                // Determine which IN endpoint to modify.
                //
                if((pucData[0] & 0x7f) == USB_EP_TO_INDEX(CONTROL_ENDPOINT))
                {
                    psInst->ucControlEndpoint =
                        INDEX_TO_USB_EP((pucData[1] & 0x7f));
                }
                else
                {
                    psInst->ucBulkINEndpoint =
                        INDEX_TO_USB_EP((pucData[1] & 0x7f));
                }
            }
            else
            {
                //
                // Extract the new endpoint number.
                //
                psInst->ucBulkOUTEndpoint =
                    INDEX_TO_USB_EP(pucData[1] & 0x7f);
            }
            break;
        }

        //
        // Handle class specific reconfiguring of the configuration descriptor
        // once the composite class has built the full descriptor.
        //
        case USB_EVENT_COMP_CONFIG:
        {
            //
            // This sets the bFirstInterface of the Interface Association
            // descriptor to the first interface which is the control
            // interface used by this instance.
            //
            pucData[2] = psInst->ucInterfaceControl;

            //
            // This sets the bMasterInterface of the Union descriptor to the
            // Control interface and the bSlaveInterface of the Union
            // Descriptor to the Data interface used by this instance.
            //
            pucData[29] = psInst->ucInterfaceControl;
            pucData[30] = psInst->ucInterfaceData;

            //
            // This sets the bDataInterface of the Union descriptor to the
            // Data interface used by this instance.
            pucData[35] = psInst->ucInterfaceData;
            break;
        }

        default:
        {
            break;
        }
    }
}

//*****************************************************************************
//
// USB non-standard request callback.
//
// This function is called by the USB stack whenever any non-standard request
// is made to the device.  The handler should process any requests that it
// supports or stall EP0 in any unsupported cases.
//
//*****************************************************************************
static void
HandleRequests(void *pvInstance, tUSBRequest *pUSBRequest, 
                                                unsigned int ulIndex)
{
    const tUSBDCDCDevice *psDevice;
    tCDCSerInstance *psInst;
    tLineCoding sLineCoding;
    tBoolean bRetcode;
    

    ASSERT(pvInstance != 0);

    //
    // Create a device instance pointer.
    //
    psDevice = (const tUSBDCDCDevice *)pvInstance;

    //
    // Get our instance data pointer.
    //
    psInst = psDevice->psPrivateCDCSerData;

    //
    // Only handle requests meant for this interface.
    //
    if(pUSBRequest->wIndex != psInst->ucInterfaceControl)
    {
        return;
    }

    //
    // Handle each of the requests that we expect from the host.
    //
    switch(pUSBRequest->bRequest)
    {
        case USB_CDC_SEND_ENCAPSULATED_COMMAND:
        {
            //
            // This implementation makes use of no communication protocol so
            // this request is meaningless.  We stall endpoint 0 if we receive
            // it.
            //
            USBDCDStallEP0(ulIndex);
            break;
        }

        case USB_CDC_GET_ENCAPSULATED_RESPONSE:
        {
            //
            // This implementation makes use of no communication protocol so
            // this request is meaningless.  We stall endpoint 0 if we receive
            // it.
            //
            USBDCDStallEP0(ulIndex);
            break;
        }

        case USB_CDC_SET_COMM_FEATURE:
        {
            //
            // This request is apparently required by an ACM device but does
            // not appear relevant to a virtual COM port and is never used by
            // Windows (or, at least, is not seen when using Hyperterminal or
            // TeraTerm via a Windows virtual COM port).  We stall endpoint 0
            // to indicate that we do not support the request.
            //
            USBDCDStallEP0(ulIndex);
            break;
        }

        case USB_CDC_GET_COMM_FEATURE:
        {
            //
            // This request is apparently required by an ACM device but does
            // not appear relevant to a virtual COM port and is never used by
            // Windows (or, at least, is not seen when using Hyperterminal or
            // TeraTerm via a Windows virtual COM port).  We stall endpoint 0
            // to indicate that we do not support the request.
            //
            USBDCDStallEP0(ulIndex);
            break;
        }

        case USB_CDC_CLEAR_COMM_FEATURE:
        {
            //
            // This request is apparently required by an ACM device but does
            // not appear relevant to a virtual COM port and is never used by
            // Windows (or, at least, is not seen when using Hyperterminal or
            // TeraTerm via a Windows virtual COM port).  We stall endpoint 0
            // to indicate that we do not support the request.
            //
            USBDCDStallEP0(ulIndex);
            break;
        }

        //
        // Set the serial communication parameters.
        //
        case USB_CDC_SET_LINE_CODING:
        {
            //
            // Remember the request we are processing.
            //
            psInst->ucPendingRequest = USB_CDC_SET_LINE_CODING;

            //
            // Set the state to indicate we are waiting for data.
            //
            psInst->eCDCRequestState = CDC_STATE_WAIT_DATA;

            //
            // Now read the payload of the request.  We handle the actual
            // operation in the data callback once this data is received.
            //
            USBDCDRequestDataEP0(0, (unsigned char *)&psInst->sLineCoding,
                                 sizeof(tLineCoding));

            //
            // ACK what we have already received.  We must do this after
            // requesting the data or we get into a race condition where the
            // data may return before we have set the stack state appropriately
            // to receive it.
            //
            USBDevEndpointDataAck(psInst->ulUSBBase, USB_EP_0, false);

            break;
        }

        //
        // Return the serial communication parameters.
        //
        case USB_CDC_GET_LINE_CODING:
        {
            //                        
            // ACK what we have already received
            //
            USBDevEndpointDataAck(psInst->ulUSBBase, USB_EP_0, false);

            //
            // Ask the client for the current line coding.
            //
            psDevice->pfnControlCallback(psDevice->pvControlCBData,
                                        USBD_CDC_EVENT_GET_LINE_CODING, 0,
                                         &sLineCoding);
              //
            // Send the line coding information back to the host.
            //
            USBDCDSendDataEP0(0, (unsigned char *)&sLineCoding,
                              sizeof(tLineCoding));

            break;
        }

        case USB_CDC_SET_CONTROL_LINE_STATE:
        {
            //
            // ACK what we have already received
            //
            USBDevEndpointDataAck(psInst->ulUSBBase, USB_EP_0, false);

            //
            // Set the handshake lines as required.
            //
            psInst->usControlLineState = pUSBRequest->wValue;

            //
            // Remember that we are due to notify the client of a line
            // state change.
            //
            SetDeferredOpFlag(&psInst->usDeferredOpFlags,
                              CDC_DO_LINE_STATE_CHANGE, true);

            //
            // See if we can notify now.
            //
            bRetcode = CheckAndSendLineStateChange(psDevice);

            //
            // If we couldn't send the line state change request to the
            // client, block reception of more data from the host until
            // previous data is processed and we send the change request.
            //
            if(!bRetcode)
            {
                psInst->bRxBlocked = true;
            }

            break;
        }

        case USB_CDC_SEND_BREAK:
        {
            //
            // ACK what we have already received
            //
            USBDevEndpointDataAck(psInst->ulUSBBase, USB_EP_0, false);

            //
            // Keep a copy of the requested break duration.
            //
            psInst->usBreakDuration = pUSBRequest->wValue;

            //
            // Remember that we need to send a break request.
            //
            SetDeferredOpFlag(&psInst->usDeferredOpFlags,
                              CDC_DO_SEND_BREAK, true);

            //
            // Send the break request if all outstanding receive data has been
            // processed.
            //
            bRetcode = CheckAndSendBreak(psDevice, pUSBRequest->wValue);

            //
            // If we couldn't send the line coding change request to the
            // client, block reception of more data from the host until
            // previous data is processed and we send the change request.
            //
            if(!bRetcode)
            {
                psInst->bRxBlocked = true;
            }

            break;
        }

        //
        // These are valid CDC requests but not ones that an ACM device should
        // receive.
        //
        case USB_CDC_SET_AUX_LINE_STATE:
        case USB_CDC_SET_HOOK_STATE:
        case USB_CDC_PULSE_SETUP:
        case USB_CDC_SEND_PULSE:
        case USB_CDC_SET_PULSE_TIME:
        case USB_CDC_RING_AUX_JACK:
        case USB_CDC_SET_RINGER_PARMS:
        case USB_CDC_GET_RINGER_PARMS:
        case USB_CDC_SET_OPERATION_PARMS:
        case USB_CDC_GET_OPERATION_PARMS:
        case USB_CDC_SET_LINE_PARMS:
        case USB_CDC_GET_LINE_PARMS:
        case USB_CDC_DIAL_DIGITS:
        case USB_CDC_SET_UNIT_PARAMETER:
        case USB_CDC_GET_UNIT_PARAMETER:
        case USB_CDC_CLEAR_UNIT_PARAMETER:
        case USB_CDC_GET_PROFILE:
        case USB_CDC_SET_ETHERNET_MULTICAST_FILTERS:
        case USB_CDC_SET_ETHERNET_POWER_MANAGEMENT_PATTERN_FILTER:
        case USB_CDC_GET_ETHERNET_POWER_MANAGEMENT_PATTERN_FILTER:
        case USB_CDC_SET_ETHERNET_PACKET_FILTER:
        case USB_CDC_GET_ETHERNET_STATISTIC:
        case USB_CDC_SET_ATM_DATA_FORMAT:
        case USB_CDC_GET_ATM_DEVICE_STATISTICS:
        case USB_CDC_SET_ATM_DEFAULT_VC:
        case USB_CDC_GET_ATM_VC_STATISTICS:
        {
            USBDCDStallEP0(ulIndex);
            break;
        }

        default:
        {
            //
            // This request is not part of the CDC specification.
            //
            USBDCDStallEP0(ulIndex);
            break;
        }
    }
}

//*****************************************************************************
//
// This function is called by the USB device stack whenever the device is
// disconnected from the host.
//
//*****************************************************************************
static void
HandleDisconnect(void *pvInstance)
{
    const tUSBDCDCDevice *psCDCDevice;
    tCDCSerInstance *psInst;

    ASSERT(pvInstance != 0);

    //
    // Create the instance pointer.
    //
    psCDCDevice = (const tUSBDCDCDevice *)pvInstance;

    //
    // Get a pointer to our instance data.
    //
    psInst = psCDCDevice->psPrivateCDCSerData;

    //
    // If we are not currently connected and we have a control callback,
    // let the client know we are open for business.
    //
    if(psInst->bConnected)
    {
        //
        // Pass the disconnected event to the client.
        //
        psCDCDevice->pfnControlCallback(psCDCDevice->pvControlCBData,
                                        USB_EVENT_DISCONNECTED, 0, (void *)0);
    }

    //
    // Remember that we are no longer connected.
    //
    psInst->bConnected = false;
}

//*****************************************************************************
//
// This function is called by the USB device stack whenever the bus is put into
// suspend state.
//
//*****************************************************************************
static void
HandleSuspend(void *pvInstance)
{
    const tUSBDCDCDevice *psCDCDevice;

    ASSERT(pvInstance != 0);

    //
    // Create the instance pointer.
    //
    psCDCDevice = (const tUSBDCDCDevice *)pvInstance;

    //
    // Pass the event on to the client.
    //
    psCDCDevice->pfnControlCallback(psCDCDevice->pvControlCBData,
                                    USB_EVENT_SUSPEND, 0, (void *)0);
}

//*****************************************************************************
//
// This function is called by the USB device stack whenever the bus is taken
// out of suspend state.
//
//*****************************************************************************
static void
HandleResume(void *pvInstance)
{
    tUSBDCDCDevice *psCDCDevice;

    ASSERT(pvInstance != 0);

    //
    // Create the instance pointer.
    //
    psCDCDevice = (tUSBDCDCDevice *)pvInstance;

    //
    // Pass the event on to the client.
    //
    psCDCDevice->pfnControlCallback(psCDCDevice->pvControlCBData,
                                    USB_EVENT_RESUME, 0, (void *)0);
}

//*****************************************************************************
//
// This function is called periodically and provides us with a time reference
// and method of implementing delayed or time-dependent operations.
//
// \param ulIndex is the index of the USB controller for which this tick
// is being generated.
// \param ulTimemS is the elapsed time in milliseconds since the last call
// to this function.
//
// \return None.
//
//*****************************************************************************
static void
CDCTickHandler(void *pvInstance, unsigned int ulTimemS, unsigned int ulIndex)
{
    tBoolean bCanSend;
    const tUSBDCDCDevice *psDevice;
    tCDCSerInstance *psInst;
    unsigned int ulSize;

    ASSERT(pvInstance != 0);

    //
    // Create the instance pointer.
    //
    psDevice = (const tUSBDCDCDevice *)pvInstance;

    //
    // Get our instance data pointer.
    //
    psInst = psDevice->psPrivateCDCSerData;

    //
    // Is there any outstanding operation that we should try to perform?
    //
    if(psInst->usDeferredOpFlags)
    {
        //
        // Yes - we have at least one deferred operation pending.  First check
        // to see if it is time to turn off a break condition.
        //
        if(psInst->usDeferredOpFlags & (1 << CDC_DO_CLEAR_BREAK))
        {
            //
            // Will our break timer expire this time?
            //
            if(psInst->usBreakDuration <= ulTimemS)
            {
                //
                // Yes - turn off the break condition.
                //
                SendBreak(psDevice, false);
            }
            else
            {
                //
                // We have not timed out yet.  Decrement the break timer.
                //
                psInst->usBreakDuration -= (unsigned short)ulTimemS;
            }
        }

        // Now check to see if the client has any data remaining to be
        // processed.  This information is needed by the remaining deferred
        // operations which are waiting for the receive pipe to be emptied
        // before they can be carried out.
        //
        bCanSend = DeviceConsumedAllData(psDevice);

        //
        // Has all outstanding data been consumed?
        //
        if(bCanSend)
        {
            //
            // Yes - go ahead and notify the client of the various things
            // it has been asked to do while we waited for data to be
            // consumed.
            //

            //
            // Do we need to start sending a break condition?
            //
            if(psInst->usDeferredOpFlags & (1 << CDC_DO_SEND_BREAK))
            {
                SendBreak(psDevice, true);
            }

            //
            // Do we need to set the RTS/DTR states?
            //
            if(psInst->usDeferredOpFlags & (1 << CDC_DO_LINE_STATE_CHANGE))
            {
                SendLineStateChange(psDevice);
            }

            //
            // Do we need to change the line coding parameters?
            //
            if(psInst->usDeferredOpFlags & (1 << CDC_DO_LINE_CODING_CHANGE))
            {
                SendLineCodingChange(psDevice);
            }

            //
            // NOTE: We do not need to handle CDC_DO_SERIAL_STATE_CHANGE here
            // since this is handled in the transmission complete notification
            // for the control IN endpoint (ProcessNotificationToHost()).
            //

            //
            // If all the deferred operations which caused the receive channel
            // to be blocked are now handled, we can unblock receive and handle
            // any packet that is currently waiting to be received.
            //
            if(!(psInst->usDeferredOpFlags & RX_BLOCK_OPS))
            {
                //
                // We can remove the receive block.
                //
                psInst->bRxBlocked = false;
            }
        }

        //
        // Is the receive channel unblocked?
        //
        if(!psInst->bRxBlocked)
        {
            //
            // Do we have a deferred receive waiting
            //
            if(psInst->usDeferredOpFlags & (1 << CDC_DO_PACKET_RX))
            {
                //
                // Yes - how big is the waiting packet?
                //
                ulSize = USBEndpointDataAvail(psInst->ulUSBBase,
                                              psInst->ucBulkOUTEndpoint);

                // Tell the client that there is a packet waiting for it.
                //
                psDevice->pfnRxCallback(psDevice->pvRxCBData,
                                        USB_EVENT_RX_AVAILABLE, ulSize,
                                        (void *)0);
            }
        }
    }

    return;
}

//*****************************************************************************
//
//! Initializes CDC device operation when used with a composite device.
//!
//! \param ulIndex is the index of the USB controller in use.
//! \param psCDCDevice points to a structure containing parameters customizing
//! the operation of the CDC device.
//!
//! An application wishing to make use of a composite 
//! USB CDC communication channel needs to call this function.
//! This function is used for initializing an instance related information of the 
//! CDC device. 
//!
//! \return Returns NULL on failure or the psCDCDevice pointer on success.
//
//*****************************************************************************
void *
USBDCDCCompositeInit(unsigned int ulIndex, const tUSBDCDCDevice *psCDCDevice)
{
    tCDCSerInstance *psInst;
    tDeviceDescriptor *psDevDesc;

    //
    // Check parameter validity.
    //
    ASSERT(ulIndex == 0);
    ASSERT(psCDCDevice);
    ASSERT(psCDCDevice->psPrivateCDCSerData);
    ASSERT(psCDCDevice->pfnControlCallback);
    ASSERT(psCDCDevice->pfnRxCallback);
    ASSERT(psCDCDevice->pfnTxCallback);
    if(ulIndex == 0)
    {
        g_USBInstance[ulIndex].uiUSBInstance = ulIndex;
        g_USBInstance[ulIndex].uiBaseAddr = USB0_BASE;
        g_USBInstance[ulIndex].uiSubBaseAddr = USB_0_OTGBASE;
        g_USBInstance[ulIndex].uiInterruptNum = SYS_INT_USB0;
        g_USBInstance[ulIndex].uiSubInterruptNum = SYS_INT_USBSSINT;
        g_USBInstance[ulIndex].uiPHYConfigRegAddr = CFGCHIP2_USBPHYCTRL;
    }
#if (USB_NUM_INSTANCE == 2)
    else if(ulIndex == 1)
    {
        g_USBInstance[ulIndex].uiUSBInstance = ulIndex;
        g_USBInstance[ulIndex].uiBaseAddr = USB1_BASE;
        g_USBInstance[ulIndex].uiSubBaseAddr = USB_1_OTGBASE;
        g_USBInstance[ulIndex].uiInterruptNum = SYS_INT_USB1;
        g_USBInstance[ulIndex].uiSubInterruptNum = SYS_INT_USBSSINT;
        g_USBInstance[ulIndex].uiPHYConfigRegAddr = CFGCHIP2_USB1PHYCTRL;
    }
#endif

    //
    // Create an instance pointer to the private data area.
    //
    psInst = psCDCDevice->psPrivateCDCSerData;

    //
    // Set the default endpoint and interface assignments.
    //
    psInst->ucBulkINEndpoint = DATA_IN_ENDPOINT;
    psInst->ucBulkOUTEndpoint = DATA_OUT_ENDPOINT;
    psInst->ucInterfaceControl = SERIAL_INTERFACE_CONTROL;
    psInst->ucInterfaceData = SERIAL_INTERFACE_DATA;

    //
    // By default do not use the interrupt control endpoint.  The single
    // instance CDC serial device will turn this on in USBDCDCInit();
    //
    psInst->ucControlEndpoint = CONTROL_ENDPOINT;

    //
    // Initialize the workspace in the passed instance structure.
    //
    psInst->psConfDescriptor = (tConfigDescriptor *)g_pCDCSerDescriptor;
    psInst->psDevInfo = &g_sCDCSerDeviceInfo;
    psInst->ulUSBBase = g_USBInstance[ulIndex].uiBaseAddr;
    psInst->eCDCRxState = CDC_STATE_UNCONFIGURED;
    psInst->eCDCTxState = CDC_STATE_UNCONFIGURED;
    psInst->eCDCInterruptState = CDC_STATE_UNCONFIGURED;
    psInst->eCDCRequestState = CDC_STATE_UNCONFIGURED;
    psInst->ucPendingRequest = 0;
    psInst->usBreakDuration = 0;
    psInst->usSerialState = 0;
    psInst->usDeferredOpFlags = 0;
    psInst->usControlLineState = 0;
    psInst->bRxBlocked = false;
    psInst->bControlBlocked = false;
    psInst->bConnected = false;

    //
    // Fix up the device descriptor with the client-supplied values.
    //
    psDevDesc = (tDeviceDescriptor *)psInst->psDevInfo->pDeviceDescriptor;
    psDevDesc->idVendor = psCDCDevice->usVID;
    psDevDesc->idProduct = psCDCDevice->usPID;

    //
    // Fix up the configuration descriptor with client-supplied values.
    //
    psInst->psConfDescriptor->bmAttributes = psCDCDevice->ucPwrAttributes;
    psInst->psConfDescriptor->bMaxPower =
                (unsigned char)(psCDCDevice->usMaxPowermA / 2);

    //
    // Plug in the client's string stable to the device information
    // structure.
    //
    psInst->psDevInfo->ppStringDescriptors = psCDCDevice->ppStringDescriptors;
    psInst->psDevInfo->ulNumStringDescriptors
            = psCDCDevice->ulNumStringDescriptors;

    //
    // Register our tick handler (this must be done after USBDCDInit).
    //
    InternalUSBRegisterTickHandler(USB_TICK_HANDLER_DEVICE,
                                   CDCTickHandler,
                                   (void *)psCDCDevice);

    //
    // Return the pointer to the instance indicating that everything went well.
    //
    return((void *)psCDCDevice);
}

//*****************************************************************************
//
//! Initializes CDC device operation for a given USB controller.
//!
//! \param ulIndex is the index of the USB controller which is to be
//! initialized for CDC device operation.
//! \param psCDCDevice points to a structure containing parameters customizing
//! the operation of the CDC device.
//!
//! An application wishing to make use of a USB CDC communication channel and
//! appear as a virtual serial port on the host system must call this function
//! to initialize the USB controller and attach the device to the USB bus.
//! This function performs all required USB initialization.
//!
//! The value returned by this function is the \e psCDCDevice pointer passed
//! to it if successful.  This pointer must be passed to all later calls to the
//! CDC class driver to identify the device instance.
//!
//! The USB CDC device class driver  offers packet-based transmit and receive
//! operation.  If the application would rather use block based communication
//! with transmit and receive buffers, USB buffers on the transmit and receive
//! channels may be used to offer this functionality.
//!
//! Transmit Operation:
//!
//! Calls to USBDCDCPacketWrite() must send no more than 64 bytes of data at a
//! time and may only be made when no other transmission is currently
//! outstanding.
//!
//! Once a packet of data has been acknowledged by the USB host, a
//! \b USB_EVENT_TX_COMPLETE event is sent to the application callback to
//! inform it that another packet may be transmitted.
//!
//! Receive Operation:
//!
//! An incoming USB data packet will result in a call to the application
//! callback with event \b USB_EVENT_RX_AVAILABLE.  The application must then
//! call USBDCDCPacketRead(), passing a buffer capable of holding the received
//! packet to retrieve the data and acknowledge reception to the USB host.  The
//! size of the received packet may be queried by calling
//! USBDCDCRxPacketAvailable().
//!
//! \note The application must not make any calls to the low level USB Device
//! API if interacting with USB via the CDC device class API.  Doing so
//! will cause unpredictable (though almost certainly unpleasant) behavior.
//!
//! \return Returns NULL on failure or the psCDCDevice pointer on success.
//
//*****************************************************************************
void *
USBDCDCInit(unsigned int ulIndex, const tUSBDCDCDevice *psCDCDevice)
{
    void *pvRet;
    tCDCSerInstance *psInst;

    //
    // Initialize the internal state for this class.
    //
    pvRet = USBDCDCCompositeInit(ulIndex, psCDCDevice);

    if(pvRet)
    {
        //
        // Create an instance pointer to the private data area.
        //
        psInst = psCDCDevice->psPrivateCDCSerData;

        //
        // Set the instance data for this device so that USBDCDInit() call can
        // have the instance data.
        //
        psInst->psDevInfo->pvInstance = (void *)psCDCDevice;

        //
        // Enable the default interrupt control endpoint if this class is not
        // being used in a composite device.
        //
        psInst->ucControlEndpoint = CONTROL_ENDPOINT;

        //
        // Use the configuration descriptor with the interrupt control endpoint.
        //
        psInst->psDevInfo->ppConfigDescriptors = g_pCDCSerConfigDescriptors;

        //
        // All is well so now pass the descriptors to the lower layer and put
        // the CDC device on the bus.
        //
        USBDCDInit(ulIndex, psInst->psDevInfo);
        
       
    }

    return(pvRet);
}

//*****************************************************************************
//
//! Shuts down the CDC device instance.
//!
//! \param pvInstance is the pointer to the device instance structure as returned
//! by USBDCDCInit().
//!
//! This function terminates CDC operation for the instance supplied and
//! removes the device from the USB bus.  This function should not be called
//! if the CDC device is part of a composite device and instead the
//! USBDCompositeTerm() function should be called for the full composite
//! device.
//!
//! Following this call, the \e pvInstance instance should not me used in any
//! other calls.
//!
//! \return None.
//
//*****************************************************************************
void
USBDCDCTerm(void *pvInstance)
{
    tCDCSerInstance *psInst;
    int index;

    ASSERT(pvInstance);

    //
    // Get a pointer to our instance data.
    //
    psInst = ((tUSBDCDCDevice *)pvInstance)->psPrivateCDCSerData;

    //
    // Terminate the requested instance.
    //
    USB_BASE_TO_INDEX(psInst->ulUSBBase, index);
    USBDCDTerm(index);

    psInst->ulUSBBase = 0;
    psInst->psDevInfo = (tDeviceInfo *)0;
    psInst->psConfDescriptor = (tConfigDescriptor *)0;

    return;
}

//*****************************************************************************
//
//! Sets the client-specific pointer for the control callback.
//!
//! \param pvInstance is the pointer to the device instance structure as
//! returned by USBDCDCInit().
//! \param pvCBData is the pointer that client wishes to be provided on each
//! event sent to the control channel callback function.
//!
//! The client uses this function to change the callback pointer passed in
//! the first parameter on all callbacks to the \e pfnControlCallback function
//! passed on USBDCDCInit().
//!
//! If a client wants to make runtime changes in the callback pointer, it must
//! ensure that the psCDCDevice structure passed to USBDCDCInit() resides in
//! RAM.  If this structure is in flash, callback pointer changes will not be
//! possible.
//!
//! \return Returns the previous callback pointer that was being used for
//! this instance's control callback.
//
//*****************************************************************************
void *
USBDCDCSetControlCBData(void *pvInstance, void *pvCBData)
{
    void *pvOldValue;

    ASSERT(pvInstance);

    //
    // Set the callback pointer for the control channel after remembering the
    // previous value.
    //
    pvOldValue = ((tUSBDCDCDevice *)pvInstance)->pvControlCBData;
    ((tUSBDCDCDevice *)pvInstance)->pvControlCBData = pvCBData;

    //
    // Return the previous callback data value.
    //
    return (pvOldValue);
}

//*****************************************************************************
//
//! Sets the client-specific data parameter for the receive channel callback.
//!
//! \param pvInstance is the pointer to the device instance structure as
//! returned by USBDCDCInit().
//! \param pvCBData is the pointer that client wishes to be provided on each
//! event sent to the receive channel callback function.
//!
//! The client uses this function to change the callback pointer passed in
//! the first parameter on all callbacks to the \e pfnRxCallback function
//! passed on USBDCDCInit().
//!
//! If a client wants to make runtime changes in the callback pointer, it must
//! ensure that the psCDCDevice structure passed to USBDCDCInit() resides in
//! RAM.  If this structure is in flash, callback data changes will not be
//! possible.
//!
//! \return Returns the previous callback pointer that was being used for
//! this instance's receive callback.
//
//*****************************************************************************
void *
USBDCDCSetRxCBData(void *pvInstance, void *pvCBData)
{
    void *pvOldValue;

    ASSERT(pvInstance);

    //
    // Set the callback data for the receive channel after remembering the
    // previous value.
    //
    pvOldValue = ((tUSBDCDCDevice *)pvInstance)->pvRxCBData;
    ((tUSBDCDCDevice *)pvInstance)->pvRxCBData = pvCBData;

    //
    // Return the previous callback pointer.
    //
    return (pvOldValue);
}

//*****************************************************************************
//
//! Sets the client-specific data parameter for the transmit callback.
//!
//! \param pvInstance is the pointer to the device instance structure as
//! returned by USBDCDCInit().
//! \param pvCBData is the pointer that client wishes to be provided on each
//! event sent to the transmit channel callback function.
//!
//! The client uses this function to change the callback pointer passed in
//! the first parameter on all callbacks to the \e pfnTxCallback function
//! passed on USBDCDCInit().
//!
//! If a client wants to make runtime changes in the callback pointer, it must
//! ensure that the psCDCDevice structure passed to USBDCDCInit() resides in
//! RAM.  If this structure is in flash, callback data changes will not be
//! possible.
//!
//! \return Returns the previous callback pointer that was being used for
//! this instance's transmit callback.
//
//*****************************************************************************
void *
USBDCDCSetTxCBData(void *pvInstance, void *pvCBData)
{
    void *pvOldValue;

    ASSERT(pvInstance);

    //
    // Set the callback data for the transmit channel after remembering the
    // previous value.
    //
    pvOldValue = ((tUSBDCDCDevice *)pvInstance)->pvTxCBData;
    ((tUSBDCDCDevice *)pvInstance)->pvTxCBData = pvCBData;

    //
    // Return the previous callback pointer.
    //
    return (pvOldValue);
}

//*****************************************************************************
//
//! Transmits a packet of data to the USB host via the CDC data interface.
//!
//! \param pvInstance is the pointer to the device instance structure as
//! returned by USBDCDCInit().
//! \param pcData points to the first byte of data which is to be transmitted.
//! \param ulLength is the number of bytes of data to transmit.
//! \param bLast indicates whether more data is to be written before a packet
//! should be scheduled for transmission.  If \b true, the client will make
//! a further call to this function.  If \b false, no further call will be
//! made and the driver should schedule transmission of a short packet.
//!
//! This function schedules the supplied data for transmission to the USB
//! host in a single USB packet.  If no transmission is currently ongoing
//! the data is immediately copied to the relevant USB endpoint FIFO.  If the
//! \e bLast parameter is \b true, the newly written packet is then scheduled
//! for transmission.  Whenever a USB packet is acknowledged by the host, a
//! USB_EVENT_TX_COMPLETE event will be sent to the application transmit
//! callback indicating that more data can now be transmitted.
//!
//! The maximum value for ulLength is 64 bytes (the maximum USB packet size
//! for the bulk endpoints in use by CDC).  Attempts to send more data than
//! this will result in a return code of 0 indicating that the data cannot be
//! sent.
//!
//! \return Returns the number of bytes actually sent.  At this level, this
//! will either be the number of bytes passed (if less than or equal to the
//! maximum packet size for the USB endpoint in use and no outstanding
//! transmission ongoing) or 0 to indicate a failure.
//
//*****************************************************************************
unsigned int
USBDCDCPacketWrite(void *pvInstance, unsigned char *pcData,
                   unsigned int ulLength, tBoolean bLast)
{
    tCDCSerInstance *psInst;
    int iRetcode;
    
    ASSERT(pvInstance);

    //
    // Get our instance data pointer
    //
    psInst = ((tUSBDCDCDevice *)pvInstance)->psPrivateCDCSerData;

    //
    // Can we send the data provided?
    //
    if((ulLength > DATA_IN_EP_MAX_SIZE) ||
       (psInst->eCDCTxState != CDC_STATE_IDLE))
    {
        //
        // Either the packet was too big or we are in the middle of sending
        // another packet.  Return 0 to indicate that we can't send this data.
        //
        return (0);
    }

    //
    // Copy the data into the USB endpoint FIFO.
    //
    iRetcode = USBEndpointDataPut(psInst->ulUSBBase,
                                  psInst->ucBulkINEndpoint, pcData,
                                  ulLength);

    //
    // Did we copy the data successfully?
    //
    if(iRetcode != -1)
    {
        //
        // Remember how many bytes we sent.
        //
        psInst->usLastTxSize += (unsigned short)ulLength;

        //
        // If this is the last call for this packet, schedule transmission.
        //
        if(bLast)
        {
            //
            // Send the packet to the host if we have received all the data we
            // can expect for this packet.
            //
            psInst->eCDCTxState = CDC_STATE_WAIT_DATA;
            iRetcode = USBEndpointDataSend(psInst->ulUSBBase,
                                           psInst->ucBulkINEndpoint,
                                           USB_TRANS_IN);
        }
    }

    //
    // Did an error occur while trying to send the data?
    //
    if(iRetcode != -1)
    {
        //
        // No - tell the caller we sent all the bytes provided.
        //
        return (ulLength);
    }
    else
    {
        //
        // Yes - tell the caller we couldn't send the data.
        //
        return (0);
    }
}

//*****************************************************************************
//
//! Reads a packet of data received from the USB host via the CDC data
//! interface.
//!
//! \param pvInstance is the pointer to the device instance structure as
//! returned by USBDCDCInit().
//! \param pcData points to a buffer into which the received data will be
//! written.
//! \param ulLength is the size of the buffer pointed to by pcData.
//! \param bLast indicates whether the client will make a further call to
//! read additional data from the packet.
//!
//! This function reads up to ulLength bytes of data received from the USB
//! host into the supplied application buffer.
//!
//! \note The \e bLast parameter is ignored in this implementation since the
//! end of a packet can be determined without relying upon the client to
//! provide this information.
//!
//! \return Returns the number of bytes of data read.
//
//*****************************************************************************
unsigned int
USBDCDCPacketRead(void *pvInstance, unsigned char *pcData,
                  unsigned int ulLength, tBoolean bLast)
{
    unsigned int ulEPStatus, ulPkt;
    unsigned int ulCount;
    tCDCSerInstance *psInst;
    int iRetcode;

    ASSERT(pvInstance);

    //
    // Get our instance data pointer
    //
    psInst = ((tUSBDCDCDevice *)pvInstance)->psPrivateCDCSerData;

    //
    // Does the relevant endpoint FIFO have a packet waiting for us?
    //
    ulEPStatus = USBEndpointStatus(psInst->ulUSBBase,
                                   psInst->ucBulkOUTEndpoint);

    if(ulEPStatus & USB_DEV_RX_PKT_RDY)
    {
        //
        // If receive is currently blocked or the buffer we were passed is
        // (potentially) too small, set the flag telling us that we have a
        // packet waiting but return 0.
        //
        if(psInst->bRxBlocked || psInst->bControlBlocked)
        {
            SetDeferredOpFlag(&psInst->usDeferredOpFlags,
                              CDC_DO_PACKET_RX, true);
            return (0);
        }
        else
        {
            //
            // It is OK to receive the new packet.  How many bytes are
            // available for us to receive?
            //
            ulPkt = USBEndpointDataAvail(psInst->ulUSBBase,
                                         psInst->ucBulkOUTEndpoint);

            //
            // Get as much data as we can.
            //
            ulCount = ulLength;
            iRetcode = USBEndpointDataGet(psInst->ulUSBBase,
                                          psInst->ucBulkOUTEndpoint,
                                          pcData, &ulCount);

            //
            // Did we read the last of the packet data?
            //
            if(ulCount == ulPkt)
            {
                //
                // Clear the endpoint status so that we know no packet is
                // waiting.
                //
                USBDevEndpointStatusClear(psInst->ulUSBBase,
                                          psInst->ucBulkOUTEndpoint,
                                          ulEPStatus);

                //
                // Acknowledge the data, thus freeing the host to send the
                // next packet.
                //
                USBDevEndpointDataAck(psInst->ulUSBBase,
                                      psInst->ucBulkOUTEndpoint,
                                      true);

                //
                // Clear the flag we set to indicate that a packet read is
                // pending.
                //
                SetDeferredOpFlag(&psInst->usDeferredOpFlags,
                                  CDC_DO_PACKET_RX, false);

            }

            //
            // If all went well, tell the caller how many bytes they got.
            //
            if(iRetcode != -1)
            {
                return (ulCount);
            }
        }
    }

    //
    // No packet was available or an error occurred while reading so tell
    // the caller no bytes were returned.
    //
    return (0);
}

//*****************************************************************************
//
//! Returns the number of free bytes in the transmit buffer.
//!
//! \param pvInstance is the pointer to the device instance structure as
//! returned by USBDCDCInit().
//!
//! This function returns the maximum number of bytes that can be passed on a
//! call to USBDCDCPacketWrite and accepted for transmission.  The value
//! returned will be the maximum USB packet size (64) if no transmission is
//! currently outstanding or 0 if a transmission is in progress.
//!
//! \return Returns the number of bytes available in the transmit buffer.
//
//*****************************************************************************
unsigned int
USBDCDCTxPacketAvailable(void *pvInstance)
{
    tCDCSerInstance *psInst;

    ASSERT(pvInstance);

    //
    // Get our instance data pointer.
    //
    psInst = ((tUSBDCDCDevice *)pvInstance)->psPrivateCDCSerData;

    //
    // Do we have a packet transmission currently ongoing?
    //
    if(psInst->eCDCTxState != CDC_STATE_IDLE)
    {
        //
        // We are not ready to receive a new packet so return 0.
        //
        return (0);
    }
    else
    {
        //
        // We can receive a packet so return the max packet size for the
        // relevant endpoint.
        //
        return (DATA_IN_EP_MAX_SIZE);
    }
}

//*****************************************************************************
//
//! Determines whether a packet is available and, if so, the size of the
//! buffer required to read it.
//!
//! \param pvInstance is the pointer to the device instance structure as
//! returned by USBDCDCInit().
//!
//! This function may be used to determine if a received packet remains to be
//! read and allows the application to determine the buffer size needed to
//! read the data.
//!
//! \return Returns 0 if no received packet remains unprocessed or the
//! size of the packet if a packet is waiting to be read.
//
//*****************************************************************************
unsigned int
USBDCDCRxPacketAvailable(void *pvInstance)
{
    unsigned int ulEPStatus;
    unsigned int ulSize;
    tCDCSerInstance *psInst;

    ASSERT(pvInstance);

    //
    // Get our instance data pointer
    //
    psInst = ((tUSBDCDCDevice *)pvInstance)->psPrivateCDCSerData;

    //
    // If receive is currently blocked, return 0.
    //
    if(psInst->bRxBlocked || psInst->bControlBlocked)
    {
        return (0);
    }

    //
    // Does the relevant endpoint FIFO have a packet waiting for us?
    //
    ulEPStatus = USBEndpointStatus(psInst->ulUSBBase,
                                   psInst->ucBulkOUTEndpoint);

    if(ulEPStatus & USB_DEV_RX_PKT_RDY)
    {
        //
        // Yes - a packet is waiting.  How big is it?
        //
        ulSize = USBEndpointDataAvail(psInst->ulUSBBase,
                                      psInst->ucBulkOUTEndpoint);

        return (ulSize);
    }
    else
    {
        //
        // There is no packet waiting to be received.
        //
        return (0);
    }
}

//*****************************************************************************
//
//! Informs the CDC module of changes in the serial control line states or
//! receive error conditions.
//!
//! \param pvInstance is the pointer to the device instance structure as
//! returned by USBDCDCInit().
//! \param usState indicates the states of the various control lines and
//! any receive errors detected.  Bit definitions are as for the USB CDC
//! SerialState asynchronous notification and are defined in header file
//! usbcdc.h.
//!
//! The application should call this function whenever the state of any of
//! the incoming RS232 handshake signals changes or in response to a receive
//! error or break condition.  The usState parameter is the ORed combination
//! of the following flags with each flag indicating the presence of that
//! condition.
//!
//! - USB_CDC_SERIAL_STATE_OVERRUN
//! - USB_CDC_SERIAL_STATE_PARITY
//! - USB_CDC_SERIAL_STATE_FRAMING
//! - USB_CDC_SERIAL_STATE_RING_SIGNAL
//! - USB_CDC_SERIAL_STATE_BREAK
//! - USB_CDC_SERIAL_STATE_TXCARRIER
//! - USB_CDC_SERIAL_STATE_RXCARRIER
//!
//! This function should be called only when the state of any flag changes.
//!
//! \return None.
//
//*****************************************************************************
void
USBDCDCSerialStateChange(void *pvInstance, unsigned short usState)
{
    tCDCSerInstance *psInst;

    ASSERT(pvInstance);

    //
    // Get our instance data pointer
    //
    psInst = ((tUSBDCDCDevice *)pvInstance)->psPrivateCDCSerData;

    //
    // Add the newly reported state bits to the current collection.  We do this
    // in case two state changes occur back-to-back before the first has been
    // notified.  There are two distinct types of signals that we report here
    // and we deal with them differently:
    //
    // 1.  Errors (overrun, parity, framing error) are ORed together so that
    //     any reported error is sent on the next notification.
    // 2.  Signal line states (RI, break, TX carrier, RX carrier) always
    //     report the last state notified to us.  The implementation here will
    //     send an interrupt showing the last state but, if two state changes
    //     occur very quickly, the host may receive a notification containing
    //     the same state that was last reported (in other words, a short pulse
    //     will be lost).  It would be possible to reduce the likelihood of
    //     this happening by building a queue of state changes and sending
    //     these in order but you are left with exactly the same problem if the
    //     queue fills up.  For now, therefore, we run the risk of missing very
    //     short pulses on the "steady-state" signal lines.
    //
    psInst->usSerialState |= (usState & USB_CDC_SERIAL_ERRORS);
    psInst->usSerialState &= ~USB_CDC_SERIAL_ERRORS;
    psInst->usSerialState |= (usState & ~USB_CDC_SERIAL_ERRORS);

    //
    // Set the flag indicating that a serial state change is to be sent.
    //
    SetDeferredOpFlag(&psInst->usDeferredOpFlags, CDC_DO_SERIAL_STATE_CHANGE,
                      true);

    //
    // Can we send the state change immediately?
    //
    if(psInst->eCDCInterruptState == CDC_STATE_IDLE)
    {
        //
        // The interrupt channel is free so send the notification immediately.
        // If we can't do this, the tick timer will catch this next time
        // round.
        //
        psInst->eCDCInterruptState = CDC_STATE_WAIT_DATA;
        SendSerialState(pvInstance);
    }

    return;
}

//*****************************************************************************
//
//! Reports the device power status (bus- or self-powered) to the USB library.
//!
//! \param pvInstance is the pointer to the CDC device instance structure.
//! \param ucPower indicates the current power status, either \b
//! USB_STATUS_SELF_PWR or \b USB_STATUS_BUS_PWR.
//!
//! Applications which support switching between bus- or self-powered
//! operation should call this function whenever the power source changes
//! to indicate the current power status to the USB library.  This information
//! is required by the USB library to allow correct responses to be provided
//! when the host requests status from the device.
//!
//! \return None.
//
//*****************************************************************************
void
USBDCDCPowerStatusSet(void *pvInstance, unsigned char ucPower)
{
    ASSERT(pvInstance);

    //
    // Pass the request through to the lower layer.
    //
    USBDCDPowerStatusSet(0, ucPower);
}

//*****************************************************************************
//
//! Requests a remote wakeup to resume communication when in suspended state.
//!
//! \param pvInstance is the pointer to the CDC device instance structure.
//!
//! When the bus is suspended, an application which supports remote wakeup
//! (advertised to the host via the config descriptor) may call this function
//! to initiate remote wakeup signaling to the host.  If the remote wakeup
//! feature has not been disabled by the host, this will cause the bus to
//! resume operation within 20mS.  If the host has disabled remote wakeup,
//! \b false will be returned to indicate that the wakeup request was not
//! successful.
//!
//! \return Returns \b true if the remote wakeup is not disabled and the
//! signaling was started or \b false if remote wakeup is disabled or if
//! signaling is currently ongoing following a previous call to this function.
//
//*****************************************************************************
tBoolean
USBDCDCRemoteWakeupRequest(void *pvInstance)
{
    ASSERT(pvInstance);

    //
    // Pass the request through to the lower layer.
    //
    return(USBDCDRemoteWakeupRequest(0));
}

//*****************************************************************************
//
// Close the Doxygen group.
//! @}
//
//*****************************************************************************