Migration guidance for EG91 LTE USB CDC modem on ESP-IDF v5.5.x (iot_usbh deprecated) (AEGHB-1397)

[Talha-DPL]

Answers checklist.

• I have read the documentation ESP-IDF Programming Guide and the issue is not addressed there.
• I have updated my IDF branch (master or release) to the latest version and checked that the issue is present there.
• I have searched the issue tracker for a similar issue and not found a similar issue.

General issue report

We are using an EG91 LTE Cat-1 module in our project. The LTE stack is currently based on the following components:

• espressif_iot_usbh_cdc
• espressif_iot_usbh_modem
• (indirect dependency on iot_usbh)

After upgrading to ESP-IDF v5.5.x, we are facing build failures because iot_usbh and related components are deprecated and no longer compatible with the updated USB Host/HCD APIs.

In addition, we previously made some local changes in:

• espressif_iot_usbh_cdc
• espressif_iot_usbh_modem

to allocate buffers in external RAM (PSRAM) instead of internal RAM.

Questions

What is the recommended migration path for projects using a USB CDC–based LTE modem (EG91) on ESP-IDF v5.5.x?

Should we completely remove espressif_iot_usbh_* and migrate to:

• esp_modem
• esp_modem_usb_dte
• usb_host_cdc_acm (ESP-IDF USB Host)?

Is there an official reference or example for using esp_modem with USB CDC modems?

Any guidance on the supported components or internal ESP-IDF APIs we should use going forward would be appreciated.

[TDA-2030]

@Talha-DPL Here is the latest driver for the 4G module, which can run under IDF 5.5.x. You can try it in the example: https://docs.espressif.com/projects/esp-iot-solution/en/latest/usb/usb_host/usb_ppp.html#example-code

If your 4G module supports ECM/RNDIS, you can also try using them.

esp_modem/esp_modem_usb_dte and espressif_iot_usbh_cdc/espressif_iot_usbh_modem have significantly different implementations. I recommend using the components I suggested above. Regarding your local code modifications, you can also re-implement them on the newer driver version.