[A request for the USB device descriptor failed]

Hello 

I have built a usb rubber with at32uc3b1256. but it does not work. when I plug it in to my computer, I receive this error :"A request for the USB device descriptor failed". could anyone tell me, what I should do? 

thanks.

 I've used a 12 MHz crystal. this is the conf_clock file:

/**
 * \file
 *
 * \brief Chip-specific system clock manager configuration
 *
 * Copyright (c) 2011 Atmel Corporation. All rights reserved.
 *
 * \asf_license_start
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * 3. The name of Atmel may not be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * 4. This software may only be redistributed and used in connection with an Atmel
 *    AVR product.
 *
 * THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
 * EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * \asf_license_stop
 *
 */
#ifndef CONF_CLOCK_H_INCLUDED
#define CONF_CLOCK_H_INCLUDED

// ===== System Clock Source Options
//#define CONFIG_SYSCLK_SOURCE        SYSCLK_SRC_RCSYS
//#define CONFIG_SYSCLK_SOURCE          SYSCLK_SRC_OSC0
#define CONFIG_SYSCLK_SOURCE        SYSCLK_SRC_PLL0

// ===== PLL0 Options
#define CONFIG_PLL0_SOURCE            PLL_SRC_OSC0
//#define CONFIG_PLL0_SOURCE          PLL_SRC_OSC1
#define CONFIG_PLL0_MUL               2 /* Fpll = (Fclk * PLL_mul) / PLL_div */
#define CONFIG_PLL0_DIV               2 /* Fpll = (Fclk * PLL_mul) / PLL_div */

// ===== PLL1 Options
#define CONFIG_PLL1_SOURCE          PLL_SRC_OSC0
//#define CONFIG_PLL1_SOURCE          PLL_SRC_OSC1
#define CONFIG_PLL1_MUL             8 /* Fpll = (Fclk * PLL_mul) / PLL_div */
#define CONFIG_PLL1_DIV             2 /* Fpll = (Fclk * PLL_mul) / PLL_div */

// ===== System Clock Bus Division Options
//#define CONFIG_SYSCLK_CPU_DIV       1 /* Fcpu = Fsys/(2 ^ CPU_div) */
//#define CONFIG_SYSCLK_PBA_DIV       1 /* Fpba = Fsys/(2 ^ PBA_div) */
//#define CONFIG_SYSCLK_PBB_DIV       1 /* Fpbb = Fsys/(2 ^ PBB_div) */

// ===== Peripheral Clock Management Options
//#define CONFIG_SYSCLK_INIT_CPUMASK  ((1 << SYSCLK_SYSTIMER) | (1 << SYSCLK_OCD))
//#define CONFIG_SYSCLK_INIT_PBAMASK  (1 << SYSCLK_USART0)
//#define CONFIG_SYSCLK_INIT_PBBMASK  (1 << SYSCLK_HMATRIX)
//#define CONFIG_SYSCLK_INIT_HSBMASK  (1 << SYSCLK_MDMA_HSB)

// ===== USB Clock Source Options
//#define CONFIG_USBCLK_SOURCE        USBCLK_SRC_OSC0
//#define CONFIG_USBCLK_SOURCE          USBCLK_SRC_PLL0
#define CONFIG_USBCLK_SOURCE        USBCLK_SRC_PLL1
#define CONFIG_USBCLK_DIV             1 /* Fusb = Fsys/(2 ^ USB_div) */

#endif /* CONF_CLOCK_H_INCLUDED */
 

 

and this is the conf_usb.h file:

 

/**
 * \file
 *
 * \brief USB configuration file
 *
 * Copyright (c) 2009 Atmel Corporation. All rights reserved.
 *
 * \asf_license_start
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * 3. The name of Atmel may not be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * 4. This software may only be redistributed and used in connection with an Atmel
 *    AVR product.
 *
 * THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
 * EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * \asf_license_stop
 *
 */

#ifndef _CONF_USB_H_
#define _CONF_USB_H_

#include "compiler.h"

/**
 * USB Device Configuration
 * @{
 */

//! Device definition (mandatory)
#define  USB_DEVICE_VENDOR_ID             USB_VID_ATMEL
#define  USB_DEVICE_PRODUCT_ID            USB_PID_ATMEL_AVR_HIDKEYBOARD
#define  USB_DEVICE_MAJOR_VERSION         1
#define  USB_DEVICE_MINOR_VERSION         0
#define  USB_DEVICE_POWER                 100 // Consumption on Vbus line (mA)
#define  USB_DEVICE_ATTR                  \
    (USB_CONFIG_ATTR_REMOTE_WAKEUP|USB_CONFIG_ATTR_SELF_POWERED)
//    (USB_CONFIG_ATTR_REMOTE_WAKEUP|USB_CONFIG_ATTR_BUS_POWERED)
//    (USB_CONFIG_ATTR_SELF_POWERED)
//    (USB_CONFIG_ATTR_BUS_POWERED)

//! USB Device string definitions (Optional)
#define  USB_DEVICE_MANUFACTURE_NAME      "ALVAND"
#define  USB_DEVICE_PRODUCT_NAME          "HAMEDAN"
// #define  USB_DEVICE_SERIAL_NAME           "12...EF"

/**
 * Device speeds support
 * @{
 */
//! To define a Low speed device
//#define  USB_DEVICE_LOW_SPEED

//! To authorize the High speed
#if (UC3A3||UC3A4)
//#define  USB_DEVICE_HS_SUPPORT
#endif
//@}

/**
 * USB Device Callbacks definitions (Optional)
 * @{
 */
#define  UDC_VBUS_EVENT(b_vbus_high)      main_vbus_action(b_vbus_high)
#define  UDC_SOF_EVENT()                  main_sof_action()
#define  UDC_SUSPEND_EVENT()              main_suspend_action()
#define  UDC_RESUME_EVENT()               main_resume_action()
//! Mandatory when USB_DEVICE_ATTR authorizes remote wakeup feature
#define  UDC_REMOTEWAKEUP_ENABLE()        main_remotewakeup_enable()
#define  UDC_REMOTEWAKEUP_DISABLE()       main_remotewakeup_disable()
//! When a extra string descriptor must be supported
//! other than manufacturer, product and serial string
// #define  UDC_GET_EXTRA_STRING()
//@}

//@}

/**
 * USB Interface Configuration
 * @{
 */
/**
 * Configuration of HID Keyboard interface
 * @{
 */
//! Interface callback definition
#define  UDI_HID_KBD_ENABLE_EXT()       main_kbd_enable()
#define  UDI_HID_KBD_DISABLE_EXT()      main_kbd_disable()
#define  UDI_HID_KBD_CHANGE_LED(value)  ui_kbd_led(value)
//@}
//@}

/**
 * USB Device Driver Configuration
 * @{
 */
//@}

//! The includes of classes and other headers must be done at the end of this file to avoid compile error
#include "udi_hid_kbd_conf.h"
#include "main.h"
#include "ui.h"

#endif // _CONF_USB_H_
 

and this is my main.c file:

/**
 * \file
 *
 * \brief Main functions for Keyboard example
 *
 * Copyright (c) 2009-2011 Atmel Corporation. All rights reserved.
 *
 * \asf_license_start
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * 3. The name of Atmel may not be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * 4. This software may only be redistributed and used in connection with an Atmel
 *    AVR product.
 *
 * THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
 * EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * \asf_license_stop
 *
 */

#include "compiler.h"
#include "preprocessor.h"
#include "board.h"
#include "gpio.h"
#include "sysclk.h"
#include "sleepmgr.h"
#include "conf_usb.h"
#include "udc.h"
#include "udd.h"
#include "ui.h"

//volatile static bool main_b_kbd_enable = false;
volatile static bool main_b_kbd_enable = true;

/*! \brief Main function. Execution starts here.
 */
int main(void)
{
    irq_initialize_vectors();
    cpu_irq_enable();

    // Initialize the sleep manager
    sleepmgr_init();

    sysclk_init();

    
    board_init();
    ui_init();
    ui_powerdown();
    ui_wakeup_enable();
volatile uint32_t freq = sysclk_get_cpu_hz();
freq ++;
LED_Toggle(LED3);

    // Start USB stack to authorize VBus monitoring
    udc_start();
    //udc_attach();
    
    if (!udc_include_vbus_monitoring()) {
        // VBUS monitoring is not available on this product
        // thereby VBUS has to be considered as present
        main_vbus_action(true);
    }

    // The main loop manages only the power mode
    // because the USB management is done by interrupt
    while (true) {
#ifdef   USB_DEVICE_LOW_SPEED
        // No USB "Keep a live" interrupt available in low speed
        // to scan keyboard interface then use main loop
        if (main_b_kbd_enable) {
            static uint16_t virtual_sof_sub = 0;
            if (700 == virtual_sof_sub++) {
                virtual_sof_sub = 0;
                static uint16_t virtual_sof = 0;
                ui_process(virtual_sof++);
            }
        }
#else
        sleepmgr_enter_sleep();
#endif
    }
}

void main_vbus_action(bool b_high)
{
    //if (b_high) {
        // Attach USB Device
        udc_attach();
    //} else {
        // VBUS not present
        //udc_detach();
    //}
}

void main_suspend_action(void)
{
    ui_powerdown();
}

void main_resume_action(void)
{
    ui_wakeup();
}

void main_sof_action(void)
{
    if (!main_b_kbd_enable)
        return;
    ui_process(udd_get_frame_number());
}

void main_remotewakeup_enable(void)
{
    ui_wakeup_enable();
}

void main_remotewakeup_disable(void)
{
    ui_wakeup_disable();
}

bool main_kbd_enable(void)
{
    main_b_kbd_enable = true;
    return true;
}

void main_kbd_disable(void)
{
    main_b_kbd_enable = false;
}

/**
 * \mainpage ASF USB Device HID Keyboard
 *
 * \section intro Introduction
 * This example shows how to implement a USB Device HID Keyboard
 * on Atmel MCU with USB module.
 * The application note AVR4903 provides information about this implementation.
 *
 * \section startup Startup
 * The example uses the buttons or sensors available on the board
 * to simulate a standard keyboard.
 * After loading firmware, connect the board (EVKxx,XPlain,...) to the USB Host.
 * When connected to a USB host system this application provides a keyboard application
 * in the Unix/Mac/Windows operating systems.
 * This example uses the native HID driver for these operating systems.
 *
 * \copydoc UI
 *
 * \section example About example
 *
 * The example uses the following module groups:
 * - Basic modules:
 *   Startup, board, clock, interrupt, power management
 * - USB Device stack and HID modules:
 *   <br>services/usb/
 *   <br>services/usb/udc/
 *   <br>services/usb/class/hid/
 *   <br>services/usb/class/hid/keyboard/
 * - Specific implementation:
 *    - main.c,
 *      <br>initializes clock
 *      <br>initializes interrupt
 *      <br>manages UI
 *    - specific implementation for each target "./examples/product_board/":
 *       - conf_foo.h   configuration of each module
 *       - ui.c        implement of user's interface (buttons, leds)
 */