STM32_UVC示例

/** @page AUDIO_Standalone USB Device AUDIO example @verbatim ******************** (C) COPYRIGHT 2015 STMicroelectronics ******************* * @file USB_Device/AUDIO_Standalone/readme.txt * @author MCD Application Team * @version V1.2.0 * @date 19-June-2015 * @brief Description of the USB Device AUDIO example. ****************************************************************************** * * Licensed under MCD-ST Liberty SW License Agreement V2, (the "License"); * You may not use this file except in compliance with the License. * You may obtain a copy of the License at: * * http://www.st.com/software_license_agreement_liberty_v2 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * ****************************************************************************** @endverbatim @par Example Description This application shows how to use the implementation of the audio streaming (Out: Speaker/Headset) capability. It follows the "Universal Serial Bus Device Class Definition for Audio Devices Release 1.0 March 18, 1998" defined by the USB Implementers Forum for reprogramming an application through USB-FS-Device. Following this specification, it is possible to manage only Full Speed USB mode (High Speed is not supported). This class is natively supported by most Operating Systems: no need for specific driver setup. This is a typical example on how to use the STM32F3xx USB Device peripheral and SAI peripheral to stream audio data from USB Host to the audio codec implemented on the STM32373C-EVAL board. 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 72 MHz. The Full Speed (FS) USB module uses internally a 48-MHz clock, which is generated from an integrated PLL. The device supports the following audio features: - Pulse Coded Modulation (PCM) format - sampling rate: 48KHz. - Bit resolution: 16 - Number of channels: 2 - No volume control - Mute/Unmute capability - Asynchronous Endpoints In order to overcome the difference between USB clock domain and STM32 clock domain, the Add-Remove mechanism is implemented at class driver level. This is a basic solution that doesn't require external components. It is based on adding/removing one sample at a periodic basis to speedup or slowdown the audio output process. This allows to resynchronize it with the input flow. @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 need to ensure that the SysTick time base is always set to 1 millisecond to have correct HAL operation. It is possible to remappe the USB interrupts (USB_LP and USB_WKUP) on interrupt lines 75 and 76. User can select USB line Interrupt through macro defined in main.h. (USE_USB_INTERRUPT_DEFAULT and USE_USB_INTERRUPT_REMAPPED) @note To reduce the example footprint, the toolchain dynamic allocation is replaced by a static allocation by returning the address of a pre-defined static buffer with the HID class structure size. It is possible to fine tune needed USB Device features by modifying defines values in USBD configuration file �usbd_conf.h� available under the project includes directory, in a way to fit the application requirements, such as: - USBD_AUDIO_FREQ, specifing the sampling rate conversion from original audio file sampling rate to the sampling rate supported by the device. @par Directory contents - USB_Device/AUDIO_Standalone/Src/main.c Main program - USB_Device/AUDIO_Standalone/Src/system_stm32f3xx.c STM32F3xx system clock configuration file - USB_Device/AUDIO_Standalone/Src/stm32f3xx_it.c Interrupt handlers - USB_Device/AUDIO_Standalone/Src/usbd_audio_if.c USBD Audio interface - USB_Device/AUDIO_Standalone/Src/usbd_conf.c General low level driver configuration - USB_Device/AUDIO_Standalone/Src/usbd_desc.c USB device AUDIO descriptor - USB_Device/AUDIO_Standalone/Inc/main.h Main program header file - USB_Device/AUDIO_Standalone/Inc/stm32f3xx_it.h Interrupt handlers header file - USB_Device/AUDIO_Standalone/Inc/stm32f3xx_hal_conf.h HAL configuration file - USB_Device/AUDIO_Standalone/Inc/usbd_conf.h USB device driver Configuration file - USB_Device/AUDIO_Standalone/Inc/usbd_desc.h USB device AUDIO descriptor header file - USB_Device/AUDIO_Standalone/Inc/usbd_audio_if.h USBD Audio interface header file @par Hardware and Software environment - This example runs on STM32F373xx devices. - This example has been tested with STMicroelectronics STM32373C-EVAL RevC evaluation boards and can be easily tailored to any other supported device and development board. - STM32373C-EVAL RevC Set-up - Connect the STM32373C-EVAL board to the PC for audio streaming through 'USB A-Male to A-Male' cable to the connector - Use CN21 connector to connect the board to external headset @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 example - Open an audio player application (Windows Media Player) and play music on the PC host * <h3><center>&copy; COPYRIGHT STMicroelectronics</center></h3> */