<div dir="auto">I was thinking along these lines, <a href="https://github.com/chegewara/esp-idf/tree/master/examples/peripherals/usb/tusb_serial_device">https://github.com/chegewara/esp-idf/tree/master/examples/peripherals/usb/tusb_serial_device</a><div dir="auto"><br></div><div dir="auto"><a href="https://docs.espressif.com/projects/esp-idf/en/latest/esp32s2/api-reference/peripherals/usb_device.html">https://docs.espressif.com/projects/esp-idf/en/latest/esp32s2/api-reference/peripherals/usb_device.html</a><br></div><div dir="auto"><br></div><div dir="auto">by using the usb lines to transfer data the current Uart level shift is not needed and it does not rely on the simcom firmware supporting gsm multiplexing on the serial interface.</div></div>