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/**
@page CDC_Standalone USB Device Communication (CDC) application
@verbatim
******************************************************************************
* @file USB_Device/CDC_Standalone/readme.txt
* @author MCD Application Team
* @brief Description of the USB Device CDC application.
******************************************************************************
*
* Copyright (c) 2019-2021 STMicroelectronics.
* All rights reserved.
*
* This software is licensed under terms that can be found in the LICENSE file
* in the root directory of this software component.
* If no LICENSE file comes with this software, it is provided AS-IS.
*
******************************************************************************
@endverbatim
@par Application Description
This application describes how to use USB device application based on the Device
Communication Class (CDC) following the PSTN sub-protocol on the STM32WBxx devices.
This example is part of the USB Device Library package using STM32Cube firmware.
This is a typical application on how to use the stm32wbxx USB OTG Device peripheral where the STM32 MCU
behaves as a USB-to-UART bridge following the Virtual COM Port (VCP) implementation.
- On one side, the STM32 exchanges data with a PC host through USB interface in Device mode.
- On the other side, the STM32 exchanges data with other devices (same host, other host,
other devices…).
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 clock (SYSCLK).
When the VCP application is started, the STM32 MCU is enumerated as serial communication port and is
configured in the same way (baudrate, data format, parity, stop bit) as it would configure a standard
COM port. The 7-bit data length with no parity control is NOT supported.
During enumeration phase, three communication pipes "endpoints" are declared in the CDC class
implementation (PSTN sub-class):
- 1 x Bulk IN endpoint for receiving data from STM32 device to PC host:
When data are received over UART they are saved in the buffer "UserTxBufferFS". Periodically, in a
timer callback the state of the buffer "UserTxBufferFS" is checked. If there are available data, they
are transmitted in response to IN token otherwise it is NAKed.
- 1 x Bulk OUT endpoint for transmitting data from PC host to STM32 device:
When data are received through this endpoint they are saved in the buffer "UserRxBufferFS" then they
are transmitted over UART using DMA mode and in meanwhile the OUT endpoint is NAKed.
Once the transmission is over, the OUT endpoint is prepared to receive next packet in
HAL_UART_TxCpltCallback().
- 1 x Interrupt IN endpoint for setting and getting serial-port parameters:
When control setup is received, the corresponding request is executed in CDC_Control_FS().
In this application, two requests are implemented:
- Set line: Set the bit rate, number of Stop bits, parity, and number of data bits
- Get line: Get the bit rate, number of Stop bits, parity, and number of data bits
The other requests (send break, control line state) are not implemented.
@note Receiving data over UART is handled by interrupt while transmitting is handled by DMA allowing
hence the application to receive data at the same time it is transmitting another data (full-
duplex feature).
The support of the VCP interface is managed through the ST Virtual COM Port driver available for
download from www.st.com.
@note The user has to check the list of the COM ports in Device Manager to find out the number of the
COM ports that have been assigned (by OS) to the VCP interface.
This application uses UART as a communication interface. The UART instance and associated resources
(GPIO, NVIC) can be tailored in "usbd_cdc_if.h" header file according to your hardware
configuration. Moreover, this application can be customized to communicate with interfaces other than UART.
For that purpose a template CDC interface is provided in:
Middlewares/ST/STM32_USB_Device_Library/Class/CDC/Src directory.
To run this application, the user can use one of the following configuration:
- Configuration 1:
By default the USART interface available of the microcontroller is connected to ST-LINK MCU. (The USART
communication between the target MCU and ST-LINK MCU is enabled.) The choice can be changed by
setting the related jumpers.
- Configuration 2:
Connect USB cable to Host and connect UART TX pin to UART RX pin on the P-NUCLEO-WB55 board
(Loopback mode). In this case, you can open one terminal (relative to USB com port)
and all data sent from this terminal will be received by the same terminal in loopback mode.
This mode is useful for test and performance measurements.
@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 Device library, please refer to UM1734
"STM32Cube USB Device library".
@par Keywords
Connectivity, USB_Device, USB, CDC, Virtual COM Port
@par Directory contents
- USB_Device/CDC_Standalone/Core/Src/main.c Main program
- USB_Device/CDC_Standalone/Core/Src/system_stm32wbxx.c STM32WBxx system clock configuration file
- USB_Device/CDC_Standalone/Core/Src/stm32wbxx_it.c Interrupt handlers
- USB_Device/CDC_Standalone/Core/Src/stm32wbxx_hal_msp.c HAL MSP Module
- USB_Device/CDC_Standalone/USB_Device/App/usb_device.c USB Device application code
- USB_Device/CDC_Standalone/USB_Device/App/usb_desc.c USB device descriptor
- USB_Device/CDC_Standalone/USB_Device/App/usbd_cdc_if.c CDC interface
- USB_Device/CDC_Standalone/USB_Device/Target/usbd_conf.c General low level driver configuration
- USB_Device/CDC_Standalone/Core/Inc/main.h Main program header file
- USB_Device/CDC_Standalone/Core/Inc/stm32wbxx_it.h Interrupt handlers header file
- USB_Device/CDC_Standalone/Core/Inc/stm32wbxx_hal_conf.h HAL configuration file
- USB_Device/CDC_Standalone/USB_Device/App/usb_device.h USB Device application header file
- USB_Device/CDC_Standalone/USB_Device/App/usbd_desc.h USB device descriptor header file
- USB_Device/CDC_Standalone/USB_Device/App/usbd_cdc_if.h CDC interface header file
- USB_Device/CDC_Standalone/USB_Device/Target/usbd_conf.h USB device driver Configuration file
@par Hardware and Software environment
- This example runs on STM32WBxx devices.
- This example has been tested with STMicroelectronics P-NUCLEO-WB55
board and can be easily tailored to any other supported device and development board.
- P-NUCLEO-WB55 Set-up
- Connect the P-NUCLEO-WB55 board CN1 to the PC through micro A-Male to standard A Male cable.
- The USART1 interface available on PB6 and PB7 of the microcontroller is
connected to ST-LINK MCU. By default connect to USART ComPORT using ST-Link interface.
(For loopback mode test: connect directly USART1 TX and RX pins.)
- Hyperterminal configuration:
- BaudRate = 115200 baud
- Word Length = 8 Bits
- Stop Bit = 1
- Parity = None
- Flow control = None
@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
- Install the USB virtual COM port driver
- Find out the number of the COM port assigned to the STM32 CDC device
- Open a serial terminal application and start the communication
* <h3><center>© COPYRIGHT STMicroelectronics</center></h3>
*/
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