[dkuenzel]

The LilyGo_T-Echo-Lite_companion_radio_usb env was missing -D ENABLE_USB_INTERFACE.

Without this flag, ArduinoSerialInterface is never registered with the MultiSerialInterface in main.cpp:

#if defined(ENABLE_USB_INTERFACE)
  usb_serial_interface.begin(Serial);
  interface_manager.addInterface(InterfaceType::USB, &usb_serial_interface);
#endif

The result: the USB CDC port enumerates correctly (the device shows up as a serial port), but checkRecvFrame and writeFrame are never called for it — the companion protocol is silently inactive. No frame the host sends receives a response.

Every other companion_radio_usb build in the codebase carries this flag; the T-Echo Lite was the only exception.

Verified against v1.18.0: flashing the device with non_shell_companion_radio_usb (which already has -D ENABLE_USB_INTERFACE) restores USB companion connectivity immediately. The one-line fix in this PR applies the same correction to the display-capable build.

[liamcottle]

Hey, thanks for the PR. I missed this env when doing the migration. Can you please update the PR to target the dev branch. PRs must be opened against dev, and not main.

[dkuenzel]

Sure thing! :-)

[liamcottle]

Thanks. It's still pulling in commits from main branch though, since you made your commits against main, and only changed the target branch on GitHub. You'd need to rebase your local branch against dev and force push here again.