Hi all!
I’ve found only one tread very similar to mine, so maybe I’ll be lucky here 
The situation:
I use RM Boxer with external HM ES900TX module, ELRS ver. - 3.5.1, backpack version - 1.5.1.
On the other side - RX betafpv SuperD 900 with the same 3.5.1.
According to the ELRS manual I’ve set RX protocol to Mavlink, Link mode of TX to Mavlink too, Backpack telemetry - to Wi-Fi mode.
Apart from this I’ve set RSSI type, RC protocol and speed of the RX accordingly to the same manual via GCS.
I can see telemetry and switch flight modes from the FC on the Boxer’s screen, so it’s possible to make conclusion that both RX and TX parse telemetry values successfully.
But there’s problem when I try to connect TX to the laptop (Win10): if I connect it via USB-cable, Mission Planner (QGC also) identifies COM-port, but isn’t able to connect by timeout. The 2nd way is Wi-Fi: If I understand correctly, Wi-Fi of Backpack must turn on automatically after powering on (I don’t use “Home Wi-Fi”, but anyway). But it doesn’t. What did I do wrong?
And, BTW, where the ON/OFF switch for Backpack in recent releases? I’ve seen screenshots of older versions with the very first field in LUA aimed to control work of the module.
Thanks in advance!
The HM ES900TX module has DIP switches on the back and you may have simply disconnected the UART of the ESP32 from the USB, you can try the switch combinations you use for flashing.
For WIFI, try disabling Windows Defender for testing. It blocks UDP on port 14550, so you will never connect. There is some complicated method to add rules to allow UDP on port 14550 but I have not managed to do it. I switched to Linux instead.
Thank you for reply, but it’s still not clear: how Backpack Wi-Fi will work and how can I connect to it without specifically turning it via Lua->Enable Wi-Fi and without prewritten home network? So, problem isn’t that I can’t connect to it, I principally don’t observe it among available networks.
And what do you mean by “switch combination”? I’ve turned two switches for flashing Backpack via Wi-Fi but now I try to work with it in “normal operation” condition (only two of six are up).
Don’t enable it this way. Just go to backpack and select Backpack->Telemetry=Wifi.
If you have not set a home network it will open it’s own and you can connect like described in the mavlink howto. Try via USB first.