Connecting ESP32-S3 Native USB to Quectel EG800Q Modem (USB Interface)

[Noval@riod]

Hi everyone,

I’m trying to connect my ESP32-S3 (native USB host) directly to a Quectel EG800Q modem through USB, to send and receive AT commands.

What I tried

Using UART, the modem works perfectly — I can send AT commands and get replies.

When I connect through USB, I get some USB descriptor data, so the hardware connection seems okay.

But I don’t get any readable AT response — it looks like the modem is in diagnostic (DM) mode.

Setup

ESP32-S3 with native USB host

Quectel EG800Q modem

Tried in Arduino IDE → didn’t work

Switched to ESP-IDF, as it supports USB host better

What I need

Any working example of ESP32-S3 communicating with a USB modem (CDC/ACM).

How to select and open the AT port (modems usually have multiple ports: DM, NMEA, AT, and data).

Has anyone successfully sent AT commands via USB (not UART) to a Quectel modem?

Any tips, code samples, or guidance would be really helpful.
Thanks!

Note: I am new to IDF , so please explain in simple ways

[horace99]

have a look at the ESP-IDF ESP32S3 OTG VCP example https://forum.arduino.cc/t/esp32-s3-as- ... /1412367/8