/**
* \file
*
* \brief USB Device Controller (UDC)
*
* Copyright (c) 2014-2015 Atmel Corporation. All rights reserved.
*
* \asf_license_start
*
* \page License
*
* 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 microcontroller 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
*
*/
/**
* \if ASF_MANUAL
* \defgroup asfdoc_udc_group USB Device Controller (UDC)
*
* The UDC provides a high-level abstraction of the USB device.
* You can use these functions to control the main device state
* (start/attach/wakeup).
*
* All USB Device Interface (UDI) in USB Device Stack is based on UDC to support
* USB enumeration.
*
* This documentation describes common USB Device usage based on UDC, as follow:
* - \ref asfdoc_udc_api_overview
* - \ref asfdoc_udc_basic_use_case_setup
* - \ref asfdoc_udc_use_cases
*
* \section asfdoc_udc_api_overview API Overview
* @{
*
*/
/**
* \brief Authorizes the VBUS event
*
* \return True, if the VBUS monitoring is possible.
*
* See \ref asfdoc_udc_vbus_monitoring for more details.
*
*/
static inline bool udc_include_vbus_monitoring(void)
{
return udd_include_vbus_monitoring();
}
/**
* \brief Start the USB Device stack
*/
void udc_start(void);
/**
* \brief Stop the USB Device stack
*/
void udc_stop(void);
/**
* \brief Attach device to the bus when possible
*
* \warning If a VBUS control is included in driver,
* then it will attach device when an acceptable VBUS
* level from the host is detected.
*/
static inline void udc_attach(void)
{
udd_attach();
}
/**
* \brief Detaches the device from the bus
*
* The driver must remove pull-up on USB line D- or D+.
*/
static inline void udc_detach(void)
{
udd_detach();
}
/**
* \brief The USB driver sends a resume signal called \e "Upstream Resume"
*
* This is authorized only when the remote wakeup feature is enabled by host.
*/
static inline void udc_remotewakeup(void)
{
udd_send_remotewakeup();
}
/**
* \brief Returns a pointer on the current interface descriptor
*
* \return Pointer on the current interface descriptor.
*/
usb_iface_desc_t UDC_DESC_STORAGE *udc_get_interface_desc(void);
/**
* @}
* \endif
*/
/*
* Support and FAQ: visit Atmel Support
*/
/**
* \page asfdoc_udc_basic_use_case_setup USB Device Basic Setup
*
* \section asfdoc_udc_device_cfg Custom Configuration
*
* The following USB Device configuration must be included in the conf_usb.h
* file of the application:
*
* \b 1. USB_DEVICE_VENDOR_ID (Word).
*
* Vendor ID provided by USB org (Atmel 0x03EB).
*
* \b 2. USB_DEVICE_PRODUCT_ID (Word).
*
* Product ID (Referenced in usb_atmel.h).
*
* \b 3. USB_DEVICE_MAJOR_VERSION (Byte).
*
* Major version of the device.
*
* \b 4. USB_DEVICE_MINOR_VERSION (Byte).
*
* Minor version of the device.
*
* \b 5. USB_DEVICE_MANUFACTURE_NAME (string).
*
* ASCII name for the manufacture.
*
* \b 6. USB_DEVICE_PRODUCT_NAME (string).
*
* ASCII name for the product.
*
* \b 7. USB_DEVICE_SERIAL_NAME (string).
*
* ASCII name to enable and set a serial number.
*
* \b 8. USB_DEVICE_POWER (Numeric).
*
* (unit mA) Maximum device power.
*
* \b 9. USB_DEVICE_ATTR (Byte).
*
* USB attributes available:
* - USB_CONFIG_ATTR_SELF_POWERED
* - USB_CONFIG_ATTR_REMOTE_WAKEUP
*
* \note If remote wake is enabled, this defines remotewakeup callbacks.
*
* \b 10. USB_DEVICE_LOW_SPEED (Only defined).
*
* Force the USB Device to run in low speed.
*
* \b 11. USB_DEVICE_HS_SUPPORT (Only defined).
*
* Authorize the USB Device to run in high speed.
*
* \b 12. USB_DEVICE_MAX_EP (Byte).
*
* Define the maximum endpoint number used by the USB Device.
*
* This one is already defined in the UDI default configuration.
* E.g.:
* - When endpoint control 0x00, endpoint 0x01, and
* endpoint 0x82 is used, then USB_DEVICE_MAX_EP=2
* - When only endpoint control 0x00 is used, then USB_DEVICE_MAX_EP=0
* - When endpoint 0x01 and endpoint 0x81 is used, then USB_DEVICE_MAX_EP=1
* (configuration not possible on USBB interface)
*
* \section asfdoc_udc_vbus_monitoring VBUS Monitoring
*
* The VBUS monitoring is used only for USB SELF Power application.
*
* - By default the USB device is automatically attached when VBUS is high
* or when USB starts for devices without internal VBUS monitoring.
* conf_usb.h file does not contain definition USB_DEVICE_ATTACH_AUTO_DISABLE.
* \code
//#define USB_DEVICE_ATTACH_AUTO_DISABLE
\endcode
*
* - Add custom VBUS monitoring. conf_usb.h file contains define
* USB_DEVICE_ATTACH_AUTO_DISABLE:
* \code
#define USB_DEVICE_ATTACH_AUTO_DISABLE
\endcode
* User C-file contains:
* \code
// Authorize VBUS monitoring
if (!udc_include_vbus_monitoring()) {
// Implement custom VBUS monitoring via GPIO or other
}
Event_VBUS_present() // VBUS interrupt or GPIO interrupt or other
{
// Attach USB Device
udc_attach();
}
\endcode
*
* - Case of battery charging. conf_usb.h file contains define
* USB_DEVICE_ATTACH_AUTO_DISABLE:
* \code #define USB_DEVICE_ATTACH_AUTO_DISABLE \endcode
* User C-file contains:
* \code
Event VBUS present() // VBUS interrupt or GPIO interrupt or ..
{
// Authorize battery charging, but wait key press to start USB.
}
Event Key press()
{
// Stop batteries charging
// Start USB
udc_attach();
}
\endcode
*
* \section asfdoc_udc_basic_use_case_setup USB Device Setup Steps
*
* \subsection asfdoc_udc_basic_use_case_setup_prereq USB Device Controller (UDC) - Prerequisites
*
* Common prerequisites for all USB devices.
*
* This module is based on USB device stack full interrupt driven, and supporting
* \ref sleepmgr_group "sleepmgr".
* For AVR® and Atmel® | SMART ARM®-based SAM3/4 devices the
* \ref clk_group "clock services" is supported.
* For SAM D21 devices the \ref asfdoc_sam0_system_clock_group "clock driver" is supported.
*
* The following procedure must be executed to set up the project correctly:
* - Specify the clock configuration:
* - XMEGA® USB devices need 48MHz clock input.
* XMEGA USB devices need CPU frequency higher than 12MHz.
* You can use either an internal RC 48MHz auto calibrated by Start of Frames
* or an external OSC.
* - UC3 and SAM3/4 devices without USB high speed support need 48MHz clock input.
* You must use a PLL and an external OSC.
* - UC3 and SAM3/4 devices with USB high speed support need 12MHz clock input.
* You must use an external OSC.
* - UC3 devices with USBC hardware need CPU frequency higher than 25MHz
* - SAM D21 devices without USB high speed support need 48MHz clock input.
* You should use DFLL with USBCRM.
* - In conf_board.h, the define CONF_BOARD_USB_PORT must be added to enable USB lines.
* (Not mandatory for all boards).
* - Enable interrupts
* - Initialize the clock service
*
* The usage of \ref sleepmgr_group "sleep manager" service is optional, but recommended to reduce power
* consumption:
* - Initialize the sleep manager service
* - Activate sleep mode when the application is in IDLE state
*
* For AVR and SAM3/4 devices, add to the initialization code:
* \code
sysclk_init();
irq_initialize_vectors();
cpu_irq_enable();
board_init();
sleepmgr_init(); // Optional
\endcode
*
* For SAM D21 devices, add to the initialization code:
* \code
system_init();
irq_initialize_vectors();
cpu_irq_enable();
sleepmgr_init(); // Optional
\endcode
*
* Add to the main IDLE loop:
* \code
sleepmgr_enter_sleep(); // Optional
\endcode
*
* \subsection asfdoc_udc_basic_use_case_setup_code USB Device Controller (UDC) - Example Code
* Common example code for all USB devices.
*
* Content of conf_usb.h:
* \code
#define USB_DEVICE_VENDOR_ID 0x03EB
#define USB_DEVICE_PRODUCT_ID 0xXXXX
#define USB_DEVICE_MAJOR_VERSION 1
#define USB_DEVICE_MINOR_VERSION 0
#define USB_DEVICE_POWER 100
#define USB_DEVICE_ATTR USB_CONFIG_ATTR_BUS_POWERED
\endcode
*
* Add to application C-file:
* \code
void usb_init(void)
{
udc_start();
}
\endcode
*
* \subsection asfdoc_udc_basic_use_case_setup_flow USB Device Controller (UDC) - Workflow
* Common workflow for all USB devices.
*
* -# Ensure that conf_usb.h is available and contains the following configuration,
* which is the main USB device configuration:
* \code
// Vendor ID provided by USB org (Atmel 0x03EB)
#define USB_DEVICE_VENDOR_ID 0x03EB // Type Word
// Product ID (Atmel PID referenced in usb_atmel.h)
#define USB_DEVICE_PRODUCT_ID 0xXXXX // Type Word
// Major version of the device
#define USB_DEVICE_MAJOR_VERSION 1 // Type Byte
// Minor version of the device
#define USB_DEVICE_MINOR_VERSION 0 // Type Byte
// Maximum device power (mA)
#define USB_DEVICE_POWER 100 // Type 9-bits
// USB attributes to enable features
#define USB_DEVICE_ATTR USB_CONFIG_ATTR_BUS_POWERED // Flags
\endcode
*
* -# Call the USB device stack start function to enable stack and start USB:
* \code
udc_start();
\endcode
*
* \note In case of USB dual roles (Device and Host) managed through USB OTG connector
* (USB ID pin), the call of udc_start() must be removed and replaced by uhc_start().
* Refer to section "Dual roles" for further information in the application note:
*
* Atmel AVR4950: ASF - USB Host Stack
*
* \section udc_conf_clock conf_clock.h Examples
*
* Content of XMEGA conf_clock.h:
* \code
// Configuration based on internal RC:
// USB clock need of 48MHz
#define CONFIG_USBCLK_SOURCE USBCLK_SRC_RCOSC
#define CONFIG_OSC_RC32_CAL 48000000UL
#define CONFIG_OSC_AUTOCAL_RC32MHZ_REF_OSC OSC_ID_USBSOF
// CPU clock need of clock > 12MHz to run with USB (Here 24MHz)
#define CONFIG_SYSCLK_SOURCE SYSCLK_SRC_RC32MHZ
#define CONFIG_SYSCLK_PSADIV SYSCLK_PSADIV_2
#define CONFIG_SYSCLK_PSBCDIV SYSCLK_PSBCDIV_1_1
\endcode
*
* Content of conf_clock.h for AT32UC3A0, AT32UC3A1, and AT32UC3B devices (USBB):
* \code
// Configuration based on 12MHz external OSC:
#define CONFIG_PLL1_SOURCE PLL_SRC_OSC0
#define CONFIG_PLL1_MUL 8
#define CONFIG_PLL1_DIV 2
#define CONFIG_USBCLK_SOURCE USBCLK_SRC_PLL1
#define CONFIG_USBCLK_DIV 1 // Fusb = Fsys/(2 ^ USB_div)
\endcode
*
* Content of conf_clock.h for AT32UC3A3 and AT32UC3A4 devices (USBB with high speed support):
* \code
// Configuration based on 12MHz external OSC:
#define CONFIG_USBCLK_SOURCE USBCLK_SRC_OSC0
#define CONFIG_USBCLK_DIV 1 // Fusb = Fsys/(2 ^ USB_div)
\endcode
*
* Content of conf_clock.h for AT32UC3C, ATUCXXD, ATUCXXL3U, and ATUCXXL4U devices (USBC):
* \code
// Configuration based on 12MHz external OSC:
#define CONFIG_PLL1_SOURCE PLL_SRC_OSC0
#define CONFIG_PLL1_MUL 8
#define CONFIG_PLL1_DIV 2
#define CONFIG_USBCLK_SOURCE USBCLK_SRC_PLL1
#define CONFIG_USBCLK_DIV 1 // Fusb = Fsys/(2 ^ USB_div)
// CPU clock need of clock > 25MHz to run with USBC
#define CONFIG_SYSCLK_SOURCE SYSCLK_SRC_PLL1
\endcode
*
* Content of conf_clock.h for SAM3S, SAM3SD, and SAM4S devices (UPD: USB Peripheral Device):
* \code
// PLL1 (B) Options (Fpll = (Fclk * PLL_mul) / PLL_div)
#define CONFIG_PLL1_SOURCE PLL_SRC_MAINCK_XTAL
#define CONFIG_PLL1_MUL 16
#define CONFIG_PLL1_DIV 2
// USB Clock Source Options (Fusb = FpllX / USB_div)
#define CONFIG_USBCLK_SOURCE USBCLK_SRC_PLL1
#define CONFIG_USBCLK_DIV 2
\endcode
*
* Content of conf_clock.h for SAM3U device (UPDHS: USB Peripheral Device High Speed):
* \code
// USB Clock Source fixed at UPLL.
\endcode
*
* Content of conf_clock.h for SAM3X and SAM3A devices (UOTGHS: USB OTG High Speed):
* \code
// USB Clock Source fixed at UPLL.
#define CONFIG_USBCLK_SOURCE USBCLK_SRC_UPLL
#define CONFIG_USBCLK_DIV 1
\endcode
*
* Content of conf_clocks.h for SAM D21 devices (USB):
* \code
// System clock bus configuration
# define CONF_CLOCK_FLASH_WAIT_STATES 2
// USB Clock Source fixed at DFLL.
// SYSTEM_CLOCK_SOURCE_DFLL configuration - Digital Frequency Locked Loop
# define CONF_CLOCK_DFLL_ENABLE true
# define CONF_CLOCK_DFLL_LOOP_MODE SYSTEM_CLOCK_DFLL_LOOP_MODE_USB_RECOVERY
# define CONF_CLOCK_DFLL_ON_DEMAND true
// Set this to true to configure the GCLK when running clocks_init.
// If set to false, none of the GCLK generators will be configured in clocks_init().
# define CONF_CLOCK_CONFIGURE_GCLK true
// Configure GCLK generator 0 (Main Clock)
# define CONF_CLOCK_GCLK_0_ENABLE true
# define CONF_CLOCK_GCLK_0_RUN_IN_STANDBY true
# define CONF_CLOCK_GCLK_0_CLOCK_SOURCE SYSTEM_CLOCK_SOURCE_DFLL
# define CONF_CLOCK_GCLK_0_PRESCALER 1
# define CONF_CLOCK_GCLK_0_OUTPUT_ENABLE false
\endcode
*
*/
/**
* \if ASF_MANUAL
* \page asfdoc_udc_use_cases USB Device Advanced Use Cases
* - \subpage udc_use_case_1
* - \subpage udc_use_case_2
* - \subpage udc_use_case_3
* - \subpage udc_use_case_5
* - \subpage udc_use_case_6
* \endif
*/
/**
* \page udc_use_case_1 Change USB Speed
*
* In this use case, the USB device is used with different USB speeds.
*
* \section udc_use_case_1_setup Setup Steps
*
* Prior to implement this use case, be sure to have already
* applied the UDI module "basic use case".
*
* \section udc_use_case_1_usage Usage Steps
*
* \subsection udc_use_case_1_usage_code Example Code
* Content of conf_usb.h:
* \code
#if // Low speed
#define USB_DEVICE_LOW_SPEED
// #define USB_DEVICE_HS_SUPPORT
#elif // Full speed
// #define USB_DEVICE_LOW_SPEED
// #define USB_DEVICE_HS_SUPPORT
#elif // High speed
// #define USB_DEVICE_LOW_SPEED
#define USB_DEVICE_HS_SUPPORT
#endif
\endcode
*
* \subsection udc_use_case_1_usage_flow Workflow
* -# Ensure that conf_usb.h is available and contains the following parameters
* required for a USB device low speed (1.5Mbit/s):
* \code
#define USB_DEVICE_LOW_SPEED
//#define USB_DEVICE_HS_SUPPORT
\endcode
* -# Ensure that conf_usb.h contains the following parameters
* required for a USB device full speed (12Mbit/s):
* \code
//#define USB_DEVICE_LOW_SPEED
//#define USB_DEVICE_HS_SUPPORT
\endcode
* -# Ensure that conf_usb.h contains the following parameters
* required for a USB device high speed (480Mbit/s):
* \code
//#define USB_DEVICE_LOW_SPEED
#define USB_DEVICE_HS_SUPPORT
\endcode
*/
/**
* \page udc_use_case_2 Use USB Strings
*
* In this use case, the usual USB strings are added in the USB device.
*
* \section udc_use_case_2_setup Setup Steps
* Prior to implement this use case, be sure to have already
* applied the UDI module "basic use case".
*
* \section udc_use_case_2_usage Usage Steps
*
* \subsection udc_use_case_2_usage_code Example Code
* Content of conf_usb.h:
* \code
#define USB_DEVICE_MANUFACTURE_NAME "Manufacture name"
#define USB_DEVICE_PRODUCT_NAME "Product name"
#define USB_DEVICE_SERIAL_NAME "12...EF"
\endcode
*
* \subsection udc_use_case_2_usage_flow Workflow
* -# Ensure that conf_usb.h is available and contains the following parameters
* required to enable different USB strings:
* \code
// Static ASCII name for the manufacture
#define USB_DEVICE_MANUFACTURE_NAME "Manufacture name"
\endcode
* \code
// Static ASCII name for the product
#define USB_DEVICE_PRODUCT_NAME "Product name"
\endcode
* \code
// Static ASCII name to enable and set a serial number
#define USB_DEVICE_SERIAL_NAME "12...EF" \endcode
*/
/**
* \page udc_use_case_3 Use USB Remote Wakeup Feature
*
* In this use case, the USB remote wakeup feature is enabled.
*
* \section udc_use_case_3_setup Setup Steps
* Prior to implement this use case, be sure to have already
* applied the UDI module "basic use case".
*
* \section udc_use_case_3_usage Usage Steps
*
* \subsection udc_use_case_3_usage_code Example Code
* Content of conf_usb.h:
* \code
#define USB_DEVICE_ATTR \
(USB_CONFIG_ATTR_REMOTE_WAKEUP | USB_CONFIG_ATTR_..._POWERED)
#define UDC_REMOTEWAKEUP_ENABLE() my_callback_remotewakeup_enable()
extern void my_callback_remotewakeup_enable(void);
#define UDC_REMOTEWAKEUP_DISABLE() my_callback_remotewakeup_disable()
extern void my_callback_remotewakeup_disable(void);
\endcode
*
* Add to application C-file:
* \code
void my_callback_remotewakeup_enable(void)
{
// Enable application wakeup events (e.g. enable GPIO interrupt)
}
void my_callback_remotewakeup_disable(void)
{
// Disable application wakeup events (e.g. disable GPIO interrupt)
}
void my_interrupt_event(void)
{
udc_remotewakeup();
}
\endcode
*
* \subsection udc_use_case_3_usage_flow Workflow
* -# Ensure that conf_usb.h is available and contains the following parameters
* required to enable the remote wakeup feature:
* \code
// Authorizes the remote wakeup feature
#define USB_DEVICE_ATTR (USB_CONFIG_ATTR_REMOTE_WAKEUP | USB_CONFIG_ATTR_..._POWERED)
\endcode
* \code
// Define callback called when the host enables the remotewakeup feature
#define UDC_REMOTEWAKEUP_ENABLE() my_callback_remotewakeup_enable()
extern void my_callback_remotewakeup_enable(void);
\endcode
* \code
// Define callback called when the host disables the remotewakeup feature
#define UDC_REMOTEWAKEUP_DISABLE() my_callback_remotewakeup_disable()
extern void my_callback_remotewakeup_disable(void);
\endcode
* -# Send a remote wakeup (USB upstream):
* \code
udc_remotewakeup();
\endcode
*/
/**
* \page udc_use_case_5 Bus Power Application Recommendations
*
* In this use case, the USB device bus power feature is enabled.
* This feature requires a correct power consumption management.
*
* \section udc_use_case_5_setup Setup Steps
* Prior to implement this use case, be sure to have already
* applied the UDI module "basic use case".
*
* \section udc_use_case_5_usage Usage Steps
*
* \subsection udc_use_case_5_usage_code Example Code
* Content of conf_usb.h:
* \code
#define USB_DEVICE_ATTR (USB_CONFIG_ATTR_BUS_POWERED)
#define UDC_SUSPEND_EVENT() user_callback_suspend_action()
extern void user_callback_suspend_action(void)
#define UDC_RESUME_EVENT() user_callback_resume_action()
extern void user_callback_resume_action(void)
\endcode
*
* Add to application C-file:
* \code
void user_callback_suspend_action(void)
{
// Disable hardware component to reduce power consumption
}
void user_callback_resume_action(void)
{
// Re-enable hardware component
}
\endcode
*
* \subsection udc_use_case_5_usage_flow Workflow
* -# Ensure that conf_usb.h is available and contains the following parameters:
* \code
// Authorizes the BUS power feature
#define USB_DEVICE_ATTR (USB_CONFIG_ATTR_BUS_POWERED)
\endcode
* \code
// Define callback called when the host suspend the USB line
#define UDC_SUSPEND_EVENT() user_callback_suspend_action()
extern void user_callback_suspend_action(void);
\endcode
* \code
// Define callback called when the host or device resume the USB line
#define UDC_RESUME_EVENT() user_callback_resume_action()
extern void user_callback_resume_action(void);
\endcode
* -# Reduce power consumption in suspend mode (max. 2.5mA on VBUS):
* \code
void user_callback_suspend_action(void)
{
turn_off_components();
}
\endcode
*/
/**
* \page udc_use_case_6 USB Dynamic Serial Number
*
* In this use case, the USB serial strings are dynamic.
* For a static serial string refer to \ref udc_use_case_2.
*
* \section udc_use_case_6_setup Setup Steps
* Prior to implement this use case, be sure to have already
* applied the UDI module "basic use case".
*
* \section udc_use_case_6_usage Usage Steps
*
* \subsection udc_use_case_6_usage_code Example Code
* Content of conf_usb.h:
* \code
#define USB_DEVICE_SERIAL_NAME
#define USB_DEVICE_GET_SERIAL_NAME_POINTER serial_number
#define USB_DEVICE_GET_SERIAL_NAME_LENGTH 12
extern uint8_t serial_number[];
\endcode
*
* Add to application C-file:
* \code
uint8_t serial_number[USB_DEVICE_GET_SERIAL_NAME_LENGTH];
void init_build_usb_serial_number(void)
{
serial_number[0] = 'A';
serial_number[1] = 'B';
...
serial_number[USB_DEVICE_GET_SERIAL_NAME_LENGTH-1] = 'C';
}
\endcode
*
* \subsection udc_use_case_6_usage_flow Workflow
* -# Ensure that conf_usb.h is available and contains the following parameters
* required to enable a USB serial number string dynamically:
* \code
#define USB_DEVICE_SERIAL_NAME // Define this empty
#define USB_DEVICE_GET_SERIAL_NAME_POINTER serial_number // Give serial array pointer
#define USB_DEVICE_GET_SERIAL_NAME_LENGTH 12 // Give size of serial array
extern uint8_t serial_number[]; // Declare external serial array
\endcode
* -# Before starting USB stack, initialize the serial array:
* \code
uint8_t serial_number[USB_DEVICE_GET_SERIAL_NAME_LENGTH];
void init_build_usb_serial_number(void)
{
serial_number[0] = 'A';
serial_number[1] = 'B';
...
serial_number[USB_DEVICE_GET_SERIAL_NAME_LENGTH-1] = 'C';
}
\endcode
*/