ESP32-S3里面的usb_webcam的例子中为什么要"prevent the USB host from retrieving USB-Serial-JTAG's descriptor"?

[jacky_gong_ssh]

为什么不能保留USB-Serial-JTAG？是因为硬件限制吗？UVC和CDC不能共存？

esp-iot-solution/examples/usb/device/usb_webcam/bootloader_components/boot_hooks/boot_hooks.c

Code: Select all

 void bootloader_before_init(void)
 {
     // Disable D+ pullup, to prevent the USB host from retrieving USB-Serial-JTAG's descriptor.
     SET_PERI_REG_MASK(USB_SERIAL_JTAG_CONF0_REG, USB_SERIAL_JTAG_PAD_PULL_OVERRIDE);
     CLEAR_PERI_REG_MASK(USB_SERIAL_JTAG_CONF0_REG, USB_SERIAL_JTAG_DP_PULLUP);
     CLEAR_PERI_REG_MASK(USB_SERIAL_JTAG_CONF0_REG, USB_SERIAL_JTAG_USB_PAD_ENABLE);
 }