从OV7670输出的帧同步VSUNC信号是低电平

嗨社区，
我遵循应用笔记AN7799从原始视频数据流OV7670。我将FX3连接到主机USB 3端口，它成功地将它识别为USB组合设备，我想这工作正常。
然而，由于OV7670不支持1280×720分辨率，所以我在CyfXUVCDSCR C中修改VS帧描述符CYFXUBSSCONDATSCR，在640×480 @ 30fPS。我修改的另一个地方是UVC.C，GLPbBeCrl结构。
此外，从OV7670输出的帧同步VSUNC信号是低电平的，所以我修改了GPIF II项目并覆盖了Eclipse项目中的CyfxGPIF2CONFIG.H文件。
在重建方案后，我将FX3、AMCAP反射为640×480的视频分辨率，但是整个视频屏幕都是空白的。
UARTebug控制台输出打印UVC：完成0帧和0缓存1秒。
这里有没有我遗漏的东西？是否有这样的工作代码示例？
当做！杰基



     以下为原文
  Hi community,
    I'm following application note AN75779 to stream the raw video data from OV7670. I'm connecting the FX3 to the host USB 3.0 port, which successfully recognized it as a USB composite device, I guess that's working alright.
    However, since OV7670 does not support 1280*720 resolution, I'm modifying the VS frame descriptor CyFxUSBSSConfigDscr in cyfxuvcdscr.c, at 640*480@30fps. Another place I modified is uvc.c, the glProbeCtrl structure.
    Also, the frame sync vsync signal output from OV7670 is active low, so I modified the GPIF II project and override the cyfxgpif2config.h file in the eclipse project.
    After rebuilding the solution, I reflashed the FX3, AMCap successfully regonized the video resolution as 640*480, however, the whole video screen is all blank.
    The UART debug console output prints UVC: Completed 0 frames and 0 buffers every one second.
    Is there anything I'm missing in here? Do you have a working code sample for such?
    Regards!
Jackie