Espressif Systems ESP Faq page 105

Chapter 4. Software framework
How can I confirm if ESP32-S2/ESP32-S3 USB supports a certain USB camera or not?
ESP32-S2/ESP32-S3 USB only supports USB cameras that correspond to wMaxPacketSize Video
Streaming endpoints which include 512 bytes at the maximum. You can use USB Stream Example
<https://github.com/espressif/esp-iot-solution/tree/master/examples/usb/host/usb_camera_mic_spk>__ to
test. An error log will be printed if the camera is not supported.
What is the maximum resolution of USB cameras that ESP32-S2/ESP32-S3 support?
• If we do not consider local JPEG decoding, the bottleneck is the throughput rate of USB. The USB camera
generally adopts synchronous transmission. ESP USB has a limitation of FIFO size, which can reach 500 KB/s
at the maximum currently. Thus, if you want to achieve 15 frames, the size of each frame can only be 33 KB.
The maximum resolution that can be achieved by 33 KB depends on the compression rate, and generally it can
reach 480 * 320.
• If you take local JPEG decoding into consideration, you also need to consider whether this resolution can reach
15 frames per second.
Can the ESP32-S2/ESP32-S3 USB recognize the USB plugging and unplugging action when it is used as a
USB CDC Device?
• Yes, the USB device uses the tinyusb protocol stack, including mount and umount callback functions to response
the USB plugging and unplugging events.
• It should be noted that if this device is a self-powered USB device, please reserve a VBUS detec-
tion pin if you need to detect plugging and unplugging actions when it is powered on.
please refer to Solution of Self-Powered USB Device <https://docs.espressif.com/projects/espressif-esp-iot-
solution/en/latest/esp32/usb/usb_device_self_power.html>__.
After enabling the RNDIS and CDC functions on the ESP32-S3 USB, I found that the PC can recognize the
COM port. However, the automatic programming function of the COM port is invalid. Is it expected?
• Yes. The USB auto-programming function is implemented through the USB-Seial-JTAG peripheral, and the
USB RNDIS function is implemented through the USB-OTG peripheral. However, only one of the two pe-
ripherals can work at a moment.
• If the USB-OTG peripheral is used in the application, the automatic programming function implemented by
the USB-Seial-JTAG peripheral will not be available. But you can manually enter the download mode for USB
burning.
Does the ESP32-S2/ESP32-S3 support the USB CDC NCM protocol?
• Currently, ESP32-S2/ESP32-S3 only supports the USB CDC ECM protocol, but does not support the USB
CDC NCM protocol.
After I initialize the USB pins of ESP32-C3/ESP32-S3 to GPIO or other peripheral pins, why cannot I burn
firmware through USB?
-The USB pin of the ESP32-C3/ESP32-S3 can be initialized to GPIO or other peripheral pins. However,
please note that after the initialization, the original USB download function will be disconnected, and the
download mode cannot be entered automatically through USB. But you can manually pull down the Boot
pin (GPIO9 in ESP32-C3 and GPIO0 in ESP32-S3) to make ESP32-C3/ESP32-S3 enter the download
mode. Then you can download firmware through USB.
Espressif Systems 88
Submit Document Feedback
For detail,
Release master