/**
  @page CDC_Standalone USB Host Communication Class (CDC) application
  
  @verbatim
  ******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
  * @file    USB_Host/CDC_Standalone/readme.txt  
  * @author  MCD Application Team
  * @brief   Description of the USB Host CDC application.
  ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; Copyright (c) 2017 STMicroelectronics International N.V. 
  * All rights reserved.</center></h2>
  *
  * Redistribution and use in source and binary forms, with or without 
  * modification, are permitted, provided that the following conditions are met:
  *
  * 1. Redistribution 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. Neither the name of STMicroelectronics nor the names of other 
  *    contributors to this software may be used to endorse or promote products 
  *    derived from this software without specific written permission.
  * 4. This software, including modifications and/or derivative works of this 
  *    software, must execute solely and exclusively on microcontroller or
  *    microprocessor devices manufactured by or for STMicroelectronics.
  * 5. Redistribution and use of this software other than as permitted under 
  *    this license is void and will automatically terminate your rights under 
  *    this license. 
  *
  * THIS SOFTWARE IS PROVIDED BY STMICROELECTRONICS AND CONTRIBUTORS "AS IS" 
  * AND ANY EXPRESS, IMPLIED OR STATUTORY WARRANTIES, INCLUDING, BUT NOT 
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A 
  * PARTICULAR PURPOSE AND NON-INFRINGEMENT OF THIRD PARTY INTELLECTUAL PROPERTY
  * RIGHTS ARE DISCLAIMED TO THE FULLEST EXTENT PERMITTED BY LAW. IN NO EVENT 
  * SHALL STMICROELECTRONICS OR CONTRIBUTORS 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.
  *
  ******************************************************************************
  @endverbatim

@par Application Description

This application shows how to use the USB host application based on the Communication Class (CDC) on the STM32Fxx devices.

This is a typical application on how to use the STM32F469xx USB OTG Host peripheral to operate with an USB 
CDC device application based on the two CDC transfer directions with a dynamic serial configuration:

 - Transmission: 
   Send dummy data to the Device board, data to be transmitted is stored in CDC_TX_Buffer buffer.

 - Reception: 
   The data entered by the user using the Hyperterminal in ASCII format are transferred by the device
   board to the Host board and displayed on its LCD screen. The CDC_RX_Buffer is the buffer used for 
   data reception.
   
At the beginning of the main program the HAL_Init() function is called to reset all the peripherals,
initialize the Flash interface and the systick. The user is provided with the SystemClock_Config()
function to configure the system clock (SYSCLK) to run at 180 MHz. The Full Speed (FS) USB module uses
internally a 48-MHz clock which is coming from a specific output of two PLLs PLL or PLL SAI.
In the High Speed (HS) mode the USB clock (60 MHz) is driven by the ULPI.

The 48 MHz clock for the USB FS can be derived from one of the two following sources:
   PLL clock (clocked by the HSE): If the USB uses the PLL as clock source, the PLL clock must be programmed
    to output 48 MHz frequency (USBCLK = PLLVCO/PLLQ).
   PLLSAI clock (clocked by the HSE): If the USB uses the PLLSAI as clock source, the PLLSAI clock must be programmed
    to output 48 MHz frequency (USBCLK = PLLSAIVCO/PLLSAIP).

When the application is started, the connected USB CDC device is detected in CDC mode and 
gets initialized. The STM32 MCU behaves as a CDC Host, it enumerates the device and extracts VID, PID, 
manufacturer name, Serial no and product name information and displays it on the LCD screen. 

User can start any operations using User button:
 - "Send Data" operation starts the Data Transmission.
 - "Receive Data" operation starts the Data Reception.

@note Care must be taken when using HAL_Delay(), this function provides accurate delay (in milliseconds)
      based on variable incremented in SysTick ISR. This implies that if HAL_Delay() is called from
      a peripheral ISR process, then the SysTick interrupt must have higher priority (numerically lower)
      than the peripheral interrupt. Otherwise the caller ISR process will be blocked.
      To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.
      
@note The application needs to ensure that the SysTick time base is always set to 1 millisecond
      to have correct HAL operation.

For more details about the STM32Cube USB Host library, please refer to UM1720  
"STM32Cube USB Host library".

@par USB Library Configuration
      
It is possible to fine tune needed USB Host features by modifying defines values in USBH configuration
file usbh_conf.h available under the project includes directory, in a way to fit the application
requirements, such as:
- Level of debug: USBH_DEBUG_LEVEL
                  0: No debug messages
                  1: Only User messages are shown
                  2: User and Error messages are shown
                  3: All messages and internal debug messages are shown
   By default debug messages are displayed on the debugger IO terminal; to redirect the Library
   messages on the LCD screen, lcd_log.c driver need to be added to the application sources.


@par Directory contents

  - USB_Host/CDC_Standalone/Src/main.c                  Main program
  - USB_Host/CDC_Standalone/Src/system_stm32f4xx.c      STM32F4xx system clock configuration file
  - USB_Host/CDC_Standalone/Src/stm32f4xx_it.c          Interrupt handlers
  - USB_Host/CDC_Standalone/Src/menu.c                  CDC State Machine
  - USB_Host/CDC_Standalone/Src/usbh_conf.c             General low level driver configuration
  - USB_Host/CDC_Standalone/Src/cdc_receive.c           CDC Receive State Machine
  - USB_Host/CDC_Standalone/Src/cdc_send.c              CDC Send State Machine
  - USB_Host/CDC_Standalone/Inc/main.h                  Main program header file
  - USB_Host/CDC_Standalone/Inc/stm32f4xx_it.h          Interrupt handlers header file
  - USB_Host/CDC_Standalone/Inc/lcd_log_conf.h          LCD log configuration file
  - USB_Host/CDC_Standalone/Inc/stm32f4xx_hal_conf.h    HAL configuration file
  - USB_Host/CDC_Standalone/Inc/usbh_conf.h             USB Host driver Configuration file
 

@par Hardware and Software environment

  - This application runs on STM32F469xx devices.
    
  - This application has been tested with STMicroelectronics STM32469I-Discovery 
    boards and can be easily tailored to any other supported device 
    and development board.

  - STM32469I-Discovery Set-up
    - Plug the CDC device into the STM32469I-Discovery board 
      through 'USB micro A-Male to A-Female' cable
      - CN13: to use USB Full Speed (FS)


@par How to use it ?

In order to make the program work, you must do the following :
 - Open your preferred toolchain 
 - Rebuild all files and load your image into target memory
 - Run the application
 
 * <h3><center>&copy; COPYRIGHT STMicroelectronics</center></h3>
 */
