Upload Firmware with Telemetry Connection

I am using Pixhawk2.4.8 in a submarine with ArduSub_v3.5.3 firmware with Serial-to-Ethernet converter, and would like to upload ArduCopter firmware to be able to change BLHeli32 ESC settings through the same ethernet link, since I cannot reach USB port of Pixhawk in submarine when it is sealed. And switch back to ArduSub for operational testing.

My setup has Pixhawk Telem1 connected to Serial-to-Ethernet converter, an ethernet cable for data transmission, and an application on computer that converts UDP stream from ethernet to Com port. I can establish telemetry very well.

When want to upload firmware with;
a. QGroundControl it waits for USB connection to device forever and does nothing although telemetry data is flowing,
b. Mission Planner detects board correctly, downloads firmware and gives “Error uploading firmware” error while scanning the ports.

When change my connection setup from ethernet to SIK radios, I get the same results.

Does anyone have a solution for uploading different types of firmwares through telemetry (not the USB port)?

Best.

That will not be possible.

@dkemxr, Could you please explain the underlying technical detail?

Is it because some usb driver properties are checked by ground control station sofwares, or is it the additional data flowing from Serial0 (USB) port of Pixhawk?

Someone please correct me if i’m wrong, but as far as I understand, it is because only though the USB can the GCS get the autopilot into boot loader mode.
The serial port is a FW function, which can’t be running if you are going to erase the FW and reload another.