[参考译文] TM4C1237H6PM：CDC 类器件上的运行时 DFU

//*****************************************************************************
//
// usb_dev_serial.c - Main routines for the USB CDC serial example.
//
// Copyright (c) 2012-2020 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 revision 2.2.0.295 of the EK-TM4C123GXL Firmware Package.
//
//*****************************************************************************

#include <stdbool.h>
#include <stdint.h>
#include "inc/hw_ints.h"
#include "inc/hw_nvic.h"
#include "inc/hw_memmap.h"
#include "inc/hw_types.h"
#include "inc/hw_gpio.h"
#include "inc/hw_uart.h"
#include "inc/hw_sysctl.h"
#include "driverlib/debug.h"
#include "driverlib/fpu.h"
#include "driverlib/gpio.h"
#include "driverlib/interrupt.h"
#include "driverlib/pin_map.h"
#include "driverlib/rom.h"
#include "driverlib/rom_map.h"
#include "driverlib/sysctl.h"
#include "driverlib/systick.h"
#include "driverlib/timer.h"
#include "driverlib/uart.h"
#include "driverlib/usb.h"
#include "usblib/usblib.h"
#include "usblib/usbcdc.h"
#include "usblib/usb-ids.h"
#include "usblib/device/usbdevice.h"
#include "usblib/device/usbdcdc.h"
#include "usblib/device/usbdcomp.h"
#include "usblib/device/usbddfu-rt.h"
#include "utils/ustdlib.h"
#include "usb_serial_structs.h"
#include "utils/uartstdio.h"

//*****************************************************************************
//
//! \addtogroup example_list
//! <h1>USB Serial Device (usb_dev_serial)</h1>
//!
//! This example application turns the evaluation kit into a virtual serial
//! port when connected to the USB host system.  The application supports the
//! USB Communication Device Class, Abstract Control Model to redirect UART0
//! traffic to and from the USB host system.
//!
//! Assuming you installed TivaWare in the default directory, a driver
//! information (INF) file for use with Windows XP, Windows Vista, Windows 7,
//! and Windows 10 can be found in C:/TivaWare_C_Series-x.x/windows_drivers.
//! For Windows 2000, the required INF file is in
//! C:/TivaWare_C_Series-x.x/windows_drivers/win2K.
//
//*****************************************************************************

//*****************************************************************************
//
// Note:
//
// This example is intended to run on Tiva C Series evaluation kit hardware
// where the UARTs are wired solely for TX and RX, and do not have GPIOs
// connected to act as handshake signals.  As a result, this example mimics
// the case where communication is always possible.  It reports DSR, DCD
// and CTS as high to ensure that the USB host recognizes that data can be
// sent and merely ignores the host's requested DTR and RTS states.  "TODO"
// comments in the code indicate where code would be required to add support
// for real handshakes.
//
//*****************************************************************************

//*****************************************************************************
//
// Configuration and tuning parameters.
//
//*****************************************************************************

//*****************************************************************************
//
// The system tick rate expressed both as ticks per second and a millisecond
// period.
//
//*****************************************************************************
#define SYSTICKS_PER_SECOND 100
#define SYSTICK_PERIOD_MS (1000 / SYSTICKS_PER_SECOND)

//*****************************************************************************
//
// Variables tracking transmit and receive counts.
//
//*****************************************************************************
volatile uint32_t g_ui32UARTTxCount = 0;
volatile uint32_t g_ui32UARTRxCount = 0;
#ifdef DEBUG
uint32_t g_ui32UARTRxErrors = 0;
#endif

//*****************************************************************************
//
// The base address, peripheral ID and interrupt ID of the UART that is to
// be redirected.
//
//*****************************************************************************

//*****************************************************************************
//
// Flag indicating whether or not we are currently sending a Break condition.
//
//*****************************************************************************
static bool g_bSendingBreak = false;

//*****************************************************************************
//
// Global system tick counter
//
//*****************************************************************************
volatile uint32_t g_ui32SysTickCount = 0;

//*****************************************************************************
//
// Flags used to pass commands from interrupt context to the main loop.
//
//*****************************************************************************
#define COMMAND_PACKET_RECEIVED 0x00000001
#define COMMAND_STATUS_UPDATE   0x00000002

volatile uint32_t g_ui32Flags = 0;
char *g_pcStatus;

//*****************************************************************************
//
// Global flag indicating that a USB configuration has been set.
//
//*****************************************************************************
static volatile bool g_bUSBConfigured = false;

//*****************************************************************************
//
// Flag used to tell the main loop that it's time to pass control back to the
// boot loader for an update.
//
//*****************************************************************************
volatile bool g_bUpdateSignalled;

//*****************************************************************************
//
// A flag used to indicate whether or not we are currently connected to the USB
// host.
//
//*****************************************************************************
volatile bool g_bConnected;

//*****************************************************************************
//
// Internal function prototypes.
//
//*****************************************************************************
static void USBUARTPrimeTransmit(uint32_t ui32Base);
static void CheckForSerialStateChange(const tUSBDCDCDevice *psDevice,
                                      int32_t i32Errors);
static void SetControlLineState(uint16_t ui16State);

//*****************************************************************************
//
// The error routine that is called if the driver library encounters an error.
//
//*****************************************************************************
#ifdef DEBUG
void
__error__(char *pcFilename, uint32_t ui32Line)
{
    while(1)
    {
    }
}
#endif


//*****************************************************************************
//
// Interrupt handler for the system tick counter.
//
//*****************************************************************************
void
SysTickIntHandler(void)
{
    //
    // Update our system time.
    //
    g_ui32SysTickCount++;
}


//*****************************************************************************
//
// Set the state of the RS232 RTS and DTR signals.
//
//*****************************************************************************
static void
SetControlLineState(uint16_t ui16State)
{
    //
    // TODO: If configured with GPIOs controlling the handshake lines,
    // set them appropriately depending upon the flags passed in the wValue
    // field of the request structure passed.
    //
}

#if 1
//*****************************************************************************
//
// Set the communication parameters to use on the UART.
//
//*****************************************************************************
static bool
SetLineCoding(tLineCoding *psLineCoding)
{
    uint32_t ui32Config;
    bool bRetcode;

    //
    // Assume everything is OK until we detect any problem.
    //
    bRetcode = true;

    //
    // Word length.  For invalid values, the default is to set 8 bits per
    // character and return an error.
    //
    switch(psLineCoding->ui8Databits)
    {
        case 5:
        {
            ui32Config = UART_CONFIG_WLEN_5;
            break;
        }

        case 6:
        {
            ui32Config = UART_CONFIG_WLEN_6;
            break;
        }

        case 7:
        {
            ui32Config = UART_CONFIG_WLEN_7;
            break;
        }

        case 8:
        {
            ui32Config = UART_CONFIG_WLEN_8;
            break;
        }

        default:
        {
            ui32Config = UART_CONFIG_WLEN_8;
            bRetcode = false;
            break;
        }
    }

    //
    // Parity.  For any invalid values, we set no parity and return an error.
    //
    switch(psLineCoding->ui8Parity)
    {
        case USB_CDC_PARITY_NONE:
        {
            ui32Config |= UART_CONFIG_PAR_NONE;
            break;
        }

        case USB_CDC_PARITY_ODD:
        {
            ui32Config |= UART_CONFIG_PAR_ODD;
            break;
        }

        case USB_CDC_PARITY_EVEN:
        {
            ui32Config |= UART_CONFIG_PAR_EVEN;
            break;
        }

        case USB_CDC_PARITY_MARK:
        {
            ui32Config |= UART_CONFIG_PAR_ONE;
            break;
        }

        case USB_CDC_PARITY_SPACE:
        {
            ui32Config |= UART_CONFIG_PAR_ZERO;
            break;
        }

        default:
        {
            ui32Config |= UART_CONFIG_PAR_NONE;
            bRetcode = false;
            break;
        }
    }

    //
    // Stop bits.  Our hardware only supports 1 or 2 stop bits whereas CDC
    // allows the host to select 1.5 stop bits.  If passed 1.5 (or any other
    // invalid or unsupported value of ui8Stop, we set up for 1 stop bit but
    // return an error in case the caller needs to Stall or otherwise report
    // this back to the host.
    //
    switch(psLineCoding->ui8Stop)
    {
        //
        // One stop bit requested.
        //
        case USB_CDC_STOP_BITS_1:
        {
            ui32Config |= UART_CONFIG_STOP_ONE;
            break;
        }

        //
        // Two stop bits requested.
        //
        case USB_CDC_STOP_BITS_2:
        {
            ui32Config |= UART_CONFIG_STOP_TWO;
            break;
        }

        //
        // Other cases are either invalid values of ui8Stop or values that we
        // cannot support so set 1 stop bit but return an error.
        //
        default:
        {
            ui32Config |= UART_CONFIG_STOP_ONE;
            bRetcode = false;
            break;
        }
    }
#if 0
    //
    // Set the UART mode appropriately.
    //
    MAP_UARTConfigSetExpClk(USB_UART_BASE, MAP_SysCtlClockGet(),
                            psLineCoding->ui32Rate, ui32Config);
#endif
    //
    // Let the caller know if we had a problem or not.
    //
    return(bRetcode);
}

//*****************************************************************************
//
// Get the communication parameters in use on the UART.
//
//*****************************************************************************
static void
GetLineCoding(tLineCoding *psLineCoding)
{
    uint32_t ui32Config;
    uint32_t ui32Rate;
#if 0
    //
    // Get the current line coding set in the UART.
    //
    MAP_UARTConfigGetExpClk(USB_UART_BASE, MAP_SysCtlClockGet(), &ui32Rate,
                            &ui32Config);
    psLineCoding->ui32Rate = ui32Rate;
#endif
    //
    // Translate the configuration word length field into the format expected
    // by the host.
    //
    switch(ui32Config & UART_CONFIG_WLEN_MASK)
    {
        case UART_CONFIG_WLEN_8:
        {
            psLineCoding->ui8Databits = 8;
            break;
        }

        case UART_CONFIG_WLEN_7:
        {
            psLineCoding->ui8Databits = 7;
            break;
        }

        case UART_CONFIG_WLEN_6:
        {
            psLineCoding->ui8Databits = 6;
            break;
        }

        case UART_CONFIG_WLEN_5:
        {
            psLineCoding->ui8Databits = 5;
            break;
        }
    }

    //
    // Translate the configuration parity field into the format expected
    // by the host.
    //
    switch(ui32Config & UART_CONFIG_PAR_MASK)
    {
        case UART_CONFIG_PAR_NONE:
        {
            psLineCoding->ui8Parity = USB_CDC_PARITY_NONE;
            break;
        }

        case UART_CONFIG_PAR_ODD:
        {
            psLineCoding->ui8Parity = USB_CDC_PARITY_ODD;
            break;
        }

        case UART_CONFIG_PAR_EVEN:
        {
            psLineCoding->ui8Parity = USB_CDC_PARITY_EVEN;
            break;
        }

        case UART_CONFIG_PAR_ONE:
        {
            psLineCoding->ui8Parity = USB_CDC_PARITY_MARK;
            break;
        }

        case UART_CONFIG_PAR_ZERO:
        {
            psLineCoding->ui8Parity = USB_CDC_PARITY_SPACE;
            break;
        }
    }

    //
    // Translate the configuration stop bits field into the format expected
    // by the host.
    //
    switch(ui32Config & UART_CONFIG_STOP_MASK)
    {
        case UART_CONFIG_STOP_ONE:
        {
            psLineCoding->ui8Stop = USB_CDC_STOP_BITS_1;
            break;
        }

        case UART_CONFIG_STOP_TWO:
        {
            psLineCoding->ui8Stop = USB_CDC_STOP_BITS_2;
            break;
        }
    }
}
#endif


//*****************************************************************************
//
// This is the callback from the USB DFU runtime interface driver.
//
// \param pvCBData is ignored by this function.
// \param ui32Event is one of the valid events for a DFU device.
// \param ui32MsgParam is defined by the event that occurs.
// \param pvMsgData is a pointer to data that is defined by the event that
// occurs.
//
// This function will be called to inform the application when a change occurs
// during operation as a DFU device.  Currently, the only event passed to this
// callback is USBD_DFU_EVENT_DETACH which tells the recipient that they should
// pass control to the boot loader at the earliest, non-interrupt context
// point.
//
// \return This function will return 0.
//
//*****************************************************************************
uint32_t
DFUDetachCallback(void *pvCBData, uint32_t ui32Event, uint32_t ui32MsgData,
                  void *pvMsgData)
{
    if(ui32Event == USBD_DFU_EVENT_DETACH)
    {
        //
        // Set the flag that the main loop uses to determine when it is time
        // to transfer control back to the boot loader.  Note that we
        // absolutely DO NOT call USBDDFUUpdateBegin() here since we are
        // currently in interrupt context and this would cause bad things to
        // happen (and the boot loader to not work).
        //
        g_bUpdateSignalled = true;
    }

    return(0);
}


//*****************************************************************************
//
// Handles CDC driver notifications related to control and setup of the device.
//
// \param pvCBData is the client-supplied callback pointer for this channel.
// \param ui32Event identifies the event we are being notified about.
// \param ui32MsgValue is an event-specific value.
// \param pvMsgData is an event-specific pointer.
//
// This function is called by the CDC driver to perform control-related
// operations on behalf of the USB host.  These functions include setting
// and querying the serial communication parameters, setting handshake line
// states and sending break conditions.
//
// \return The return value is event-specific.
//
//*****************************************************************************
uint32_t
ControlHandler(void *pvCBData, uint32_t ui32Event,
               uint32_t ui32MsgValue, void *pvMsgData)
{
    uint32_t ui32IntsOff;
    tUSBDCDCDevice * pCDCDevice;

    pCDCDevice = (tUSBDCDCDevice *)pvCBData;

    // Which event are we being asked to process?
    switch(ui32Event)
    {
        // We are connected to a host and communication is now possible.
        case USB_EVENT_CONNECTED:
            g_bUSBConfigured = true;
            g_bConnected = true;

            // Flush our buffers.
            USBBufferFlush(&g_sTxBuffer);
            USBBufferFlush(&g_sRxBuffer);

            // Tell the main loop to update the display.
            ui32IntsOff = MAP_IntMasterDisable();
            g_pcStatus = "Connected";
            g_ui32Flags |= COMMAND_STATUS_UPDATE;
            if(!ui32IntsOff)
            {
                MAP_IntMasterEnable();
            }
            break;

        // The host has disconnected.
        case USB_EVENT_DISCONNECTED:
            g_bUSBConfigured = false;
            g_bConnected = false;

            ui32IntsOff = MAP_IntMasterDisable();
            g_pcStatus = "Disconnected";
            g_ui32Flags |= COMMAND_STATUS_UPDATE;
            if(!ui32IntsOff)
            {
                MAP_IntMasterEnable();
            }
            break;

#if 1
        // Return the current serial communication parameters.
        // We do not need this since there is no UART - Dhammika
        case USBD_CDC_EVENT_GET_LINE_CODING:
            GetLineCoding(pvMsgData);
            break;

        // Set the current serial communication parameters.
        // We do not need this since there is no UART - Dhammika
        case USBD_CDC_EVENT_SET_LINE_CODING:
            SetLineCoding(pvMsgData);
            break;

        // Set the current serial communication parameters.
        case USBD_CDC_EVENT_SET_CONTROL_LINE_STATE:
            SetControlLineState((uint16_t)ui32MsgValue);
            break;
#endif
        // Ignore SUSPEND and RESUME for now.
        case USB_EVENT_SUSPEND:
        case USB_EVENT_RESUME:
            break;

        // We don't expect to receive any other events.  Ignore any that show
        // up in a release build or hang in a debug build.
        default:
#ifdef DEBUG
            while(1);
#else
            break;
#endif

    }

    return(0);
}

//*****************************************************************************
//
// Handles CDC driver notifications related to the transmit channel (data to
// the USB host).
//
// \param ui32CBData is the client-supplied callback pointer for this channel.
// \param ui32Event identifies the event we are being notified about.
// \param ui32MsgValue is an event-specific value.
// \param pvMsgData is an event-specific pointer.
//
// This function is called by the CDC driver to notify us of any events
// related to operation of the transmit data channel (the IN channel carrying
// data to the USB host).
//
// \return The return value is event-specific.
//
//*****************************************************************************
uint32_t
TxHandler(void *pvCBData, uint32_t ui32Event, uint32_t ui32MsgValue,
          void *pvMsgData)
{
    // Which event have we been sent?
    switch(ui32Event)
    {
        case USB_EVENT_TX_COMPLETE:
            // Since we are using the USBBuffer, we don't need to do anything
            // here.
            break;

        // We don't expect to receive any other events.  Ignore any that show
        // up in a release build or hang in a debug build.
        default:
#ifdef DEBUG
            while(1);
#else
            break;
#endif

    }
    return(0);
}

//*****************************************************************************
//
// Handles CDC driver notifications related to the receive channel (data from
// the USB host).
//
// \param ui32CBData is the client-supplied callback data value for this channel.
// \param ui32Event identifies the event we are being notified about.
// \param ui32MsgValue is an event-specific value.
// \param pvMsgData is an event-specific pointer.
//
// This function is called by the CDC driver to notify us of any events
// related to operation of the receive data channel (the OUT channel carrying
// data from the USB host).
//
// \return The return value is event-specific.
//
//*****************************************************************************
uint32_t
RxHandler(void *pvCBData, uint32_t ui32Event, uint32_t ui32MsgValue,
          void *pvMsgData)
{
    uint32_t ui32Count;
    uint32_t ui32Read, ui32Space;
    uint8_t  ui8Char;

    // Which event are we being sent?
    switch(ui32Event)
    {
        // A new packet has been received.
        case USB_EVENT_RX_AVAILABLE:
        {
            // How much space do we have in the buffer?
            ui32Space = USBBufferSpaceAvailable((tUSBBuffer *)&g_sTxBuffer);

            // Read data from the USB until there is none left or we run
            // out of space in our Tx buffer.
            while(ui32Space)
            {
                // Read the USB buffer
                if(USBBufferRead((tUSBBuffer *)&g_sRxBuffer, &ui8Char, 1))
                {
                    // Write the rceived character back into Tx buffer
                    USBBufferWrite((tUSBBuffer *)&g_sTxBuffer, (uint8_t *)&ui8Char, 1);
                    // Decrement the number of bytes we know the buffer can accept.
                     ui32Space--;
                    // Update our count of bytes received via the USB.
                    g_ui32UARTRxCount++;
                }
                else break;
            }

            break;
        }

        // We are being asked how much unprocessed data we have still to
        // process. We send 0 if USB Tx buffer can take data
        case USB_EVENT_DATA_REMAINING:
        {
            USBBufferFlush((tUSBBuffer *)&g_sTxBuffer);
            return(0);
        }

        // We are being asked to provide a buffer into which the next packet
        // can be read. We do not support this mode of receiving data so let
        // the driver know by returning 0. The CDC driver should not be sending
        // this message but this is included just for illustration and
        // completeness.
        case USB_EVENT_REQUEST_BUFFER:
        {
            return(0);
        }

        // We don't expect to receive any other events.  Ignore any that show
        // up in a release build or hang in a debug build.
        default:
#ifdef DEBUG
            while(1);
#else
            break;
#endif
    }

    return(0);
}

//*****************************************************************************
//
// This is the main application entry function.
//
//*****************************************************************************
int
main(void)
{
    uint32_t ui32TxCount;
    uint32_t ui32RxCount;
    uint32_t ui32SysClock;

    // Enable lazy stacking for interrupt handlers.  This allows floating-point
    // instructions to be used within interrupt handlers, but at the expense of
    // extra stack usage.
    MAP_FPULazyStackingEnable();

    // Set the clocking to run from the PLL at 50MHz
    MAP_SysCtlClockSet(SYSCTL_SYSDIV_4 | SYSCTL_USE_PLL | SYSCTL_OSC_MAIN |
                       SYSCTL_XTAL_16MHZ);
    ui32SysClock = MAP_SysCtlClockGet();

    // Configure the required pins for USB operation.
    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);
    MAP_GPIOPinTypeUSBAnalog(GPIO_PORTD_BASE, GPIO_PIN_5 | GPIO_PIN_4);

    // Enable the GPIO port that is used for the on-board LED.
    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);

    // Enable the GPIO pins for the LED (PF2 & PF3).
    MAP_GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_3|GPIO_PIN_2);

    // Not configured initially.
    g_bUSBConfigured = false;

    // TODO: Add code to configure handshake GPIOs if required.

    // Enable the system tick.
    MAP_SysTickPeriodSet(ui32SysClock / SYSTICKS_PER_SECOND);
    MAP_SysTickIntEnable();
    MAP_SysTickEnable();

    // Initialize the transmit and receive buffers.
    USBBufferInit(&g_sTxBuffer);
    USBBufferInit(&g_sRxBuffer);

    // Set the USB stack mode to Device mode with VBUS monitoring.
    USBStackModeSet(0, eUSBModeForceDevice, 0);

//----------------------------------------------------------
    // Initialize each of the device instances that will form our composite
    // USB device.
    USBDCDCCompositeInit(0, &g_sCDCDevice, &(g_sCompDevice.psDevices[0]));

    USBDDFUCompositeInit(0, &g_sDFUDevice, &(g_sCompDevice.psDevices[1]));

    // Pass the USB library our device information, initialize the USB
    // controller and connect the device to the bus.
    void *pvCompositeInstance = USBDCompositeInit(0, &g_sCompDevice, DESCRIPTOR_BUFFER_SIZE, g_pui8DescriptorBuffer);
//-----------------------------------------------------------

    // Clear our local byte counters.
    ui32RxCount = 0;
    ui32TxCount = 0;

    // Main application loop.
    while(!g_bUpdateSignalled)
    {
        // Wait for USB configuration to complete.
        while(!g_bConnected)
        {
        }

        // Now keep processing the mouse as long as the host is connected and
        // we've not been told to prepare for a firmware upgrade.
        while(g_bConnected && !g_bUpdateSignalled)
        {
            // Have we been asked to update the status display?
            if(g_ui32Flags & COMMAND_STATUS_UPDATE)
            {
                //
                // Clear the command flag
                //
                MAP_IntMasterDisable();
                g_ui32Flags &= ~COMMAND_STATUS_UPDATE;
                MAP_IntMasterEnable();
            }

            //
            // Has there been any transmit traffic since we last checked?
            //
            if(ui32TxCount != g_ui32UARTTxCount)
            {
                //
                // Turn on the Green LED.
                //
                GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_3, GPIO_PIN_3);

                //
                // Delay for a bit.
                //
                SysCtlDelay(MAP_SysCtlClockGet() / 3 / 20);

                //
                // Turn off the Green LED.
                //
                GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_3, 0);

                //
                // Take a snapshot of the latest transmit count.
                //
                ui32TxCount = g_ui32UARTTxCount;
            }

            //
            // Has there been any receive traffic since we last checked?
            //
            if(ui32RxCount != g_ui32UARTRxCount)
            {
                //
                // Turn on the Blue LED.
                //
                GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_2, GPIO_PIN_2);

                //
                // Delay for a bit.
                //
                SysCtlDelay(MAP_SysCtlClockGet() / 3 / 20);

                //
                // Turn off the Blue LED.
                //
                GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_2, 0);

                //
                // Take a snapshot of the latest receive count.
                //
                ui32RxCount = g_ui32UARTRxCount;

            }
        }
    }

    // Terminate the USB device and detach from the bus.
    // USBDCompositeTerm(pvCompositeInstance);
    USBDCDTerm(0);

    // Disable all interrupts.
    MAP_IntMasterDisable();

    // Disable SysTick and its interrupt.
    MAP_SysTickIntDisable();
    MAP_SysTickDisable();

    // Disable all processor interrupts.  Instead of disabling them one at a
    // time, a direct write to NVIC is done to disable all peripheral
    // interrupts.
    HWREG(NVIC_DIS0) = 0xffffffff;
    HWREG(NVIC_DIS1) = 0xffffffff;
    HWREG(NVIC_DIS2) = 0xffffffff;
    HWREG(NVIC_DIS3) = 0xffffffff;
    HWREG(NVIC_DIS4) = 0xffffffff;

    //
    // Enable and reset the USB peripheral.
    //
    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_USB0);
    MAP_SysCtlPeripheralReset(SYSCTL_PERIPH_USB0);
    MAP_USBClockEnable(USB0_BASE, 4, USB_CLOCK_INTERNAL);

    //
    // Wait for about a second.
    //
    MAP_SysCtlDelay(ui32SysClock / 3);

    //
    // Re-enable interrupts at the NVIC level.
    //
    MAP_IntMasterEnable();

    //
    // Call the USB boot loader.
    //
    ROM_UpdateUSB(0);

    //
    // Should never get here, but just in case.
    //
    while(1)
    {
    }

}

//*****************************************************************************
//
// usb_serial_structs.c - Data structures defining this CDC USB device.
//
// Copyright (c) 2012-2020 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 revision 2.2.0.295 of the EK-TM4C123GXL Firmware Package.
//
//*****************************************************************************

#include <stdint.h>
#include <stdbool.h>
#include "inc/hw_types.h"
#include "driverlib/usb.h"
#include "usblib/usblib.h"
#include "usblib/usbcdc.h"
#include "usblib/usb-ids.h"
#include "usblib/device/usbdevice.h"
#include "usblib/device/usbdcdc.h"
#include "usb_serial_structs.h"
//*****************************************************************************
//
// The languages supported by this device.
//
//*****************************************************************************
const uint8_t g_pui8LangDescriptor[] =
{
    4,
    USB_DTYPE_STRING,
    USBShort(USB_LANG_EN_US)
};

//*****************************************************************************
//
// The manufacturer string.
//
//*****************************************************************************
const uint8_t g_pui8ManufacturerString[] =
{
    (17 + 1) * 2,
    USB_DTYPE_STRING,
    'T', 0, 'e', 0, 'x', 0, 'a', 0, 's', 0, ' ', 0, 'I', 0, 'n', 0, 's', 0,
    't', 0, 'r', 0, 'u', 0, 'm', 0, 'e', 0, 'n', 0, 't', 0, 's', 0,
};

//*****************************************************************************
//
// The product string.
//
//*****************************************************************************
const uint8_t g_pui8ProductString[] =
{
    2 + (16 * 2),
    USB_DTYPE_STRING,
    'V', 0, 'i', 0, 'r', 0, 't', 0, 'u', 0, 'a', 0, 'l', 0, ' ', 0,
    'C', 0, 'O', 0, 'M', 0, ' ', 0, 'P', 0, 'o', 0, 'r', 0, 't', 0
};

//*****************************************************************************
//
// The serial number string.
//
//*****************************************************************************
const uint8_t g_pui8SerialNumberString[] =
{
    2 + (8 * 2),
    USB_DTYPE_STRING,
    '1', 0, '2', 0, '3', 0, '4', 0, '5', 0, '6', 0, '7', 0, '8', 0
};

//*****************************************************************************
//
// The control interface description string.
//
//*****************************************************************************
const uint8_t g_pui8ControlInterfaceString[] =
{
    2 + (21 * 2),
    USB_DTYPE_STRING,
    'A', 0, 'C', 0, 'M', 0, ' ', 0, 'C', 0, 'o', 0, 'n', 0, 't', 0,
    'r', 0, 'o', 0, 'l', 0, ' ', 0, 'I', 0, 'n', 0, 't', 0, 'e', 0,
    'r', 0, 'f', 0, 'a', 0, 'c', 0, 'e', 0
};

//*****************************************************************************
//
// The configuration description string.
//
//*****************************************************************************
const uint8_t g_pui8ConfigString[] =
{
    2 + (26 * 2),
    USB_DTYPE_STRING,
    'S', 0, 'e', 0, 'l', 0, 'f', 0, ' ', 0, 'P', 0, 'o', 0, 'w', 0,
    'e', 0, 'r', 0, 'e', 0, 'd', 0, ' ', 0, 'C', 0, 'o', 0, 'n', 0,
    'f', 0, 'i', 0, 'g', 0, 'u', 0, 'r', 0, 'a', 0, 't', 0, 'i', 0,
    'o', 0, 'n', 0
};

//*****************************************************************************
//
// The descriptor string table.
//
//*****************************************************************************
const uint8_t * const g_ppui8StringDescriptors[] =
{
    g_pui8LangDescriptor,
    g_pui8ManufacturerString,
    g_pui8ProductString,
    g_pui8SerialNumberString,
    g_pui8ControlInterfaceString,
    g_pui8ConfigString
};

#define NUM_STRING_DESCRIPTORS (sizeof(g_ppui8StringDescriptors) /            \
                                sizeof(uint8_t *))

//*****************************************************************************
//
// CDC device callback function prototypes.
//
//*****************************************************************************
uint32_t RxHandler(void *pvCBData, uint32_t ui32Event,
                   uint32_t ui32MsgValue, void *pvMsgData);
uint32_t TxHandler(void *pvCBData, uint32_t ui32Event,
                   uint32_t ui32MsgValue, void *pvMsgData);
uint32_t ControlHandler(void *pvCBData, uint32_t ui32Event,
                        uint32_t ui32MsgValue, void *pvMsgData);

//*****************************************************************************
//
// The CDC device initialization and customization structures. In this case,
// we are using USBBuffers between the CDC device class driver and the
// application code. The function pointers and callback data values are set
// to insert a buffer in each of the data channels, transmit and receive.
//
// With the buffer in place, the CDC channel callback is set to the relevant
// channel function and the callback data is set to point to the channel
// instance data. The buffer, in turn, has its callback set to the application
// function and the callback data set to our CDC instance structure.
//
//*****************************************************************************
tUSBDCDCDevice g_sCDCDevice =
{
    USB_VID_TI_1CBE,
    USB_PID_SERIAL,
    500,
    USB_CONF_ATTR_SELF_PWR,
    ControlHandler,
    (void *)&g_sCDCDevice,
    USBBufferEventCallback,
    (void *)&g_sRxBuffer,
    USBBufferEventCallback,
    (void *)&g_sTxBuffer,
    g_ppui8StringDescriptors,
    NUM_STRING_DESCRIPTORS
};

//*****************************************************************************
//
// Receive buffer (from the USB perspective).
//
//*****************************************************************************
uint8_t g_pui8USBRxBuffer[UART_BUFFER_SIZE];
tUSBBuffer g_sRxBuffer =
{
    false,                          // This is a receive buffer.
    RxHandler,                      // pfnCallback
    (void *)&g_sCDCDevice,          // Callback data is our device pointer.
    USBDCDCPacketRead,              // pfnTransfer
    USBDCDCRxPacketAvailable,       // pfnAvailable
    (void *)&g_sCDCDevice,          // pvHandle
    g_pui8USBRxBuffer,              // pui8Buffer
    UART_BUFFER_SIZE,               // ui32BufferSize
};

//*****************************************************************************
//
// Transmit buffer (from the USB perspective).
//
//*****************************************************************************
uint8_t g_pui8USBTxBuffer[UART_BUFFER_SIZE];
tUSBBuffer g_sTxBuffer =
{
    true,                           // This is a transmit buffer.
    TxHandler,                      // pfnCallback
    (void *)&g_sCDCDevice,          // Callback data is our device pointer.
    USBDCDCPacketWrite,             // pfnTransfer
    USBDCDCTxPacketAvailable,       // pfnAvailable
    (void *)&g_sCDCDevice,          // pvHandle
    g_pui8USBTxBuffer,              // pui8Buffer
    UART_BUFFER_SIZE,               // ui32BufferSize
};

//*****************************************************************************
//
// The DFU runtime interface initialization and customization structures
//
//*****************************************************************************
tUSBDDFUDevice g_sDFUDevice =
{
    DFUDetachCallback,
    (void *)&g_sDFUDevice
};

//****************************************************************************
//
// The number of device class instances that this composite device will
// use.
//
//****************************************************************************
#define NUM_DEVICES             2

//****************************************************************************
//
// The array of devices supported by this composite device.
//
//****************************************************************************
tCompositeEntry g_psCompDevices[NUM_DEVICES];

//****************************************************************************
//
// Additional workspace required by the composite driver to hold a lookup
// table allowing mapping of composite interface and endpoint numbers to
// individual device class instances.
//
//****************************************************************************
uint32_t g_pui32CompWorkspace[NUM_DEVICES];

//****************************************************************************
//
// The instance data for this composite device.
//
//****************************************************************************
tCompositeInstance g_sCompInstance;

//****************************************************************************
//
// Allocate the Device Data for the top level composite device class.
//
//****************************************************************************
tUSBDCompositeDevice g_sCompDevice =
{
    // Stellaris VID.
    USB_VID_TI_1CBE,
    // PID.
    USB_PID_SERIAL,
    // This is in milliamps.
    500,
    // Bus powered device.
    USB_CONF_ATTR_SELF_PWR,
    // Device event handler function pointer (receives connect, disconnect
    // and other device-level notifications).
    ControlHandler,
    // The string table.
    g_ppui8StringDescriptors,
    NUM_STRING_DESCRIPTORS,
    // The Composite device array.
    NUM_DEVICES,
    g_psCompDevices,
};

//****************************************************************************
//
// A buffer into which the composite device can write the combined config
// descriptor.
//
//****************************************************************************
uint8_t g_pui8DescriptorBuffer[DESCRIPTOR_BUFFER_SIZE];