156 lines
8.3 KiB
Plaintext
156 lines
8.3 KiB
Plaintext
/**
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@page CDC_Standalone USB Device Communication (CDC) example
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@verbatim
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******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
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* @file USB_Device/CDC_Standalone/readme.txt
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* @author MCD Application Team
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* @brief Description of the USB Device CDC example.
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******************************************************************************
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* @attention
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*
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* <h2><center>© Copyright (c) 2016 STMicroelectronics.
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* All rights reserved.</center></h2>
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*
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* This software component is licensed by ST under Ultimate Liberty license
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* SLA0044, the "License"; You may not use this file except in compliance with
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* the License. You may obtain a copy of the License at:
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* www.st.com/SLA0044
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*
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******************************************************************************
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@endverbatim
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@par Example Description
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Use of the USB device application based on the Device Communication Class (CDC) and
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following the PSTN subprotocol. This application uses the USB Device and UART peripherals.
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This is a typical example on how to use the STM32F1xx USB Device peripheral where the STM32 MCU
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behaves as a USB-to-RS232 bridge following the Virtual COM Port (VCP) implementation.
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- On one side, the STM32 exchanges data with a PC host through USB interface in Device mode.
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- On the other side, the STM32 exchanges data with other devices (same host, other host,
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other devices…) through the UART interface (RS232).
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At the beginning of the main program the HAL_Init() function is called to reset all the peripherals,
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initialize the Flash interface and the systick. The user is provided with the SystemClock_Config()
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function to configure the system clock (SYSCLK) to run at 72 MHz.
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The Full Speed (FS) USB module uses internally a 48-MHz clock, which is generated from an integrated PLL.
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When the VCP application is started, the STM32 MCU is enumerated as serial communication port and is
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configured in the same way (baudrate, data format, parity, stop bit) as it would configure a standard
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COM port. The 7-bit data length with no parity control is NOT supported.
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During enumeration phase, three communication pipes "endpoints" are declared in the CDC class
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implementation (PSTN sub-class):
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- 1 x Bulk IN endpoint for receiving data from STM32 device to PC host:
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When data are received over UART they are saved in the buffer "UserTxBuffer". Periodically, in a
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timer callback the state of the buffer "UserTxBuffer" is checked. If there are available data, they
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are transmitted in response to IN token otherwise it is NAKed.
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The polling period depends on "CDC_POLLING_INTERVAL" value.
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- 1 x Bulk OUT endpoint for transmitting data from PC host to STM32 device:
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When data are received through this endpoint they are saved in the buffer "UserRxBuffer" then they
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are transmitted over UART using interrupt mode and in meanwhile the OUT endpoint is NAKed.
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Once the transmission is over, the OUT endpoint is prepared to receive next packet in
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HAL_UART_TxCpltCallback().
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- 1 x Interrupt IN endpoint for setting and getting serial-port parameters:
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When control setup is received, the corresponding request is executed in CDC_Itf_Control().
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In this application, two requests are implemented:
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- Set line: Set the bit rate, number of Stop bits, parity, and number of data bits
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- Get line: Get the bit rate, number of Stop bits, parity, and number of data bits
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The other requests (send break, control line state) are not implemented.
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@note Receiving data over UART is handled by interrupt while transmitting is handled by DMA allowing
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hence the application to receive data at the same time it is transmitting another data (full-
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duplex feature).
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The support of the VCP interface is managed through the ST Virtual COM Port driver available for
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download from www.st.com.
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@note The user has to check the list of the COM ports in Device Manager to find out the number of the
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COM ports that have been assigned (by OS) to the VCP interface.
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This application uses UART as a communication interface. The UART instance and associated resources
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(GPIO, NVIC) can be tailored in "usbd_cdc_interface.h" header file according to your hardware
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configuration. Moreover, this application can be customized to communicate with interfaces other than UART.
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For that purpose a template CDC interface is provided in:
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Middlewares/ST/STM32_USB_Device_Library/Class/CDC/Src directory.
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To run this application, the user can use one of the following configurations:
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- Configuration 1:
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Connect USB cable to host and UART (RS232) to a different host (PC or other device) or to same host.
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In this case, you can open two hyperterminals to send/receive data to/from host to/from device.
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Hyperterminal is configured as follows:
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- Data Length = 8 Bits
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- One Stop Bit
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- None parity
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- BaudRate = 115200 baud
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- Flow control: None
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- Configuration 2:
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Connect USB cable to Host and connect UART TX pin to UART RX pin on the STM3210E-EVAL board
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(Loopback mode). In this case, you can open one terminal (relative to USB com port or UART com port)
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and all data sent from this terminal will be received by the same terminal in loopback mode.
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This mode is useful for test and performance measurements.
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- In case of error LED3 is turned on.
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@note Care must be taken when using HAL_Delay(), this function provides accurate delay (in milliseconds)
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based on variable incremented in SysTick ISR. This implies that if HAL_Delay() is called from
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a peripheral ISR process, then the SysTick interrupt must have higher priority (numerically lower)
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than the peripheral interrupt. Otherwise the caller ISR process will be blocked.
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To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.
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@note The application need to ensure that the SysTick time base is always set to 1 millisecond
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to have correct HAL operation.
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@note To reduce the example footprint, the toolchain dynamic allocation is replaced by a static allocation
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by returning the address of a pre-defined static buffer with the CDC class structure size.
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@par Directory contents
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- USB_Device/CDC_Standalone/Src/main.c Main program
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- USB_Device/CDC_Standalone/Src/system_stm32f1xx.c STM32F1xx system clock configuration file
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- USB_Device/CDC_Standalone/Src/stm32f1xx_it.c Interrupt handlers
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- USB_Device/CDC_Standalone/Src/stm32f1xx_hal_msp.c HAL MSP module
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- USB_Device/CDC_Standalone/Src/usbd_cdc_interface.c USBD CDC interface
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- USB_Device/CDC_Standalone/Src/usbd_conf.c General low level driver configuration
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- USB_Device/CDC_Standalone/Src/usbd_desc.c USB device CDC descriptor
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- USB_Device/CDC_Standalone/Inc/main.h Main program header file
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- USB_Device/CDC_Standalone/Inc/stm32f1xx_it.h Interrupt handlers header file
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- USB_Device/CDC_Standalone/Inc/stm32f1xx_hal_conf.h HAL configuration file
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- USB_Device/CDC_Standalone/Inc/usbd_conf.h USB device driver Configuration file
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- USB_Device/CDC_Standalone/Inc/usbd_desc.h USB device descriptor header file
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- USB_Device/CDC_Standalone/Inc/usbd_cdc_interface.h USBD CDC interface header file
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@par Hardware and Software environment
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- This example runs on STM32F1xx devices.
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- This example has been tested with a STM3210E-EVAL board embedding
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a STM32F103ZGx device and can be easily tailored to any other supported device
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and development board.
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- STM3210E-EVAL Set-up
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- Connect the STM3210E-EVAL board to the PC through 'USB Type A-Male to A-Male'
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- Connect the STM3210E-EVAL board to the PC (or to another evaluation board) through RS232 (USART)
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serial cable CN12 connector.
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- For loopback mode test: remove RS232 cable on CN12 and connect directly USART TX and RX pins:
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GPIOA GPIO_PIN_9 and GPIO_PIN_10.
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@par How to use it ?
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In order to make the program work, you must do the following :
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- Open your preferred toolchain
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- Rebuild all files and load your image into target memory
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- Run the example
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- Install the USB virtual COM port driver
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- Find out the number of the COM port assigned to the STM32 CDC device
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- Open a serial terminal application and start the communication
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* <h3><center>© COPYRIGHT STMicroelectronics</center></h3>
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*/
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