HappyModel EP2 as VRx backpack

[i3v]

I am trying to make HappyModel EP2 work with VRx firmware for the RapidFire module.

However, the EP2 module behaves weird - once power-cycled, the green LED first blinks once(?) very fast, then remains solid for ~2 seconds, then slowly blinks 4 times, then remains solid forever (see video below). There seem to be no such LED status code in the docs.

This LED status does look a bit like "The Backpack is in Binding Mode", but the BINDING_PHRASE is embedded with the firmware, and thus it should be unnecessary. (The HOME_WIFI_SSID and HOME_WIFI_PASSWORD do work as expected -they are "saved", btw.) Attempting to perform Binding while it's blinking seem to change nothing at all.

When I try to actually use it ('VTX Admin" -> "Send VTx" in the Lua script), the VTx (the drone) actually switches the channel, but the VRx (the RapidFire) does not switch. I have to manually switch the channel on the RapidFire to get the picture back.

Each 3rd boot is WiFi mode (few slow blinks then constant fast blinking). This mode seem to work OK.

1. Any idea what that kind of LED blinking actually means?
2. Although EP1/EP2 is a supported and (even recommended) module, there seem to be no explicitly matching Target in the ExpressLRS Configurator v1.6.1. I tried the following:
   • "OFFICIAL RELEASES" - "Release1.1.0" - "VRX" - "Rapidfire ESP RX Backpack" / "Rapidfire ESP01F Backpack"/ "HappyModel EP82 VRX Rapidfire Backpack". Sadly, build fails with InvalidEnvNameError: Invalid environment name 'HDZero_RX5.1_ESP32_Backpack_via_WIFI'. The name can contain alphanumeric, underscore, and hyphen characters (a-z, 0-9, -, _)
   • Same for release 1.2.0
   • "OFFICIAL RELEASES" - "Release1.3.0" - "VRX" - "Rapidfire ESP01F Backpack" - the "4 slow blinks and then nothing".
   • "OFFICIAL RELEASES" - "1.4.1" - "rapidFIRE Module" - "ELRS Receiver" - the "4 slow blinks and then nothing".
   • "OFFICIAL RELEASES" - "1.4.1" - "rapidFIRE Module" - "ESP01F Module" - the "4 slow blinks and then nothing".
   • "OFFICIAL RELEASES" - "1.4.1" - "rapidFIRE Module" - "Happymodel EP82" - the "4 slow blinks and then nothing".
   • "GIT BRANCH" - "master" - "rapidFIRE Module" - "ELRS Receiver" - the "4 slow blinks and then nothing". "5917 SPI mode" is shown on the RapidFire screen.
   • "GIT BRANCH" - "master" - "rapidFIRE Module" - "ESP01F Module" - the "4 slow blinks and then nothing".
   • "GIT BRANCH" - "master" - "rapidFIRE Module" - "Happymodel EP82" - the "4 slow blinks and then nothing".

The firmware update via WiFi web page show "master (88ce11)" for both RadioMaster TX16S (mkii, ELRS) radio and the EP2 (when using "master").

WIN_20240131_10_50_43_Pro.mp4