K//Z

ELRS 3.4+ · IOS WI-FI JOYSTICK

CHECK BEFORE YOU FLASH.

The official ExpressLRS UDP/WiFi Joystick feature was introduced in ELRS 3.4.0. Killzone's native iOS flow has been physically verified on a RadioMaster Pocket running ELRS 4.1, but 4.1 is not the minimum protocol version. If your fleet is already on ELRS 3.x, stay on the 3.x major line and move to a supported 3.4+ build; if it is on 4.x, stay on 4.x. Do not cross major versions solely to get WiFi Joystick.

IMPORTANT · RF MIGRATION IS SEPARATE

Keep the transmitter and receivers on the same ELRS major line. If you are on 3.1 or 3.3, upgrade within 3.x to a supported 3.4+ release; if you are already on 4.x, choose a supported 4.x release. Do not move a transmitter from 3.x to 4.x solely for WiFi Joystick: a major-version migration requires matching receiver updates and bench testing across the fleet.

Why update?

THE UPSIDE

ELRS 3.4.0+ is the minimum feature line for this iOS app's official WiFi Joystick input. The radio must still be a supported WiFi-capable transmitter target. Newer ELRS releases can bring feature, performance, and bug-fix improvements, depending on your exact hardware and firmware options.

THE TRADE-OFF

If you are below 3.4 on the 3.x line—for example, 3.1—move within 3.x to a supported 3.4+ release. If you are already on 4.x, stay on 4.x. A move from 3.x to 4.x is a separate major-version migration that can interrupt links to older receivers; bench-test every model before trusting it in the air.

The official V3.4.0 release notes identify UDP/WiFi Joystick as the feature that avoids the Bluetooth/USB joystick restrictions on platforms such as iOS. ExpressLRS documentation describes same-major-version pairing as the compatibility assumption—for example, 3.x with 3.x. Record your current setup and keep the old firmware files until any migration is proven.

Before you flash

  1. Check the current version first. If the transmitter already reports a supported 3.4+ or 4.x build and exposes the WiFi Joystick option, try the iOS path before flashing anything. If you are below 3.4 on 3.x, update within 3.x; if you are on 4.x, stay on 4.x. The feature does not require a 3.x-to-4.x fleet migration.
  2. Back up the radio. If an update is needed, copy the radio's SD card and model data somewhere safe. Write down the binding phrase, regulatory domain, packet-rate choices, and any other custom options you rely on.
  3. Inventory your fleet. List each receiver and the drone it belongs to. A transmitter major-version update can leave an otherwise healthy drone link unavailable until that receiver is updated with the matching target and options.
  4. Identify the exact target. In the official ExpressLRS Web Flasher ↗, select the exact internal transmitter target and the deliberate release line for your hardware. Do not choose by brand name alone, and do not flash a file made for a different target.
  5. Plan time for testing. Keep the radio, every receiver you plan to update, a flight battery, and a safe bench area available. Do not start the migration immediately before a flight.

If you do need to update the radio

  1. Update the internal radio BIN. Open the official ExpressLRS Web Flasher ↗ in another tab. Select the release line you intentionally chose, the exact internal transmitter target, and your required firmware options, then build and download the target-specific .bin. On the radio, open the current ExpressLRS Lua script and choose WiFi Connectivity → Enable WiFi. Join the ExpressLRS TX network from your computer; if it says there is no internet, choose Join Without Internet. Open http://10.0.0.1, or use http://elrs_tx.local if home Wi-Fi is configured, and upload the BIN. Do not unplug or power off the radio until the update finishes and the Lua screen returns.
  2. Update the Lua script. Download the current official elrs.lua from the ExpressLRS Lua Script guide ↗. Before replacing anything, find the old elrs.lua or elrs v3.lua in the radio's SCRIPTS/TOOLS folder and copy it to your computer or another safe backup location so you can revert easily. Then delete the old script from the radio before copying in the new one; do not leave both versions in the folder. Use either method:

    USB Storage: Power the radio on, connect it to the computer with a USB data cable, and choose USB Storage when the radio asks for a USB mode. The radio's SD card will mount as a drive; copy elrs.lua into SCRIPTS/TOOLS.

    SD card: Power the radio off, remove the microSD card, insert it into the computer with a card reader, and copy elrs.lua into SCRIPTS/TOOLS.

    Safely eject the drive or card, put it back in the radio, and open the ExpressLRS script from the radio's Tools menu. The Lua script is separate from firmware: updating the BIN does not update the script.

Then update your receivers

The transmitter BIN and Lua script only update the radio. Preserve the current RF major line whenever possible: a 3.x fleet should move from 3.1/3.3 to a supported 3.4+ build within 3.x, while a 4.x fleet should stay on 4.x. If you intentionally move the radio from ELRS 3.x to 4.x, build and flash matching receiver BINs for every drone before flying; a 4.x transmitter and 3.x receiver are not a drop-in pair. Staying within the current major line avoids that migration.

Do not flash a BIN made for the wrong target. After each receiver update, restore only the settings the documented workflow requires and bench-test that model before flying.

After the update

  1. Power the radio and receiver on the bench with propellers removed.
  2. Confirm every updated receiver connects, the expected model responds, and the flight controller sees the correct channel order and arm switch.
  3. Test failsafe behavior and range in a controlled area before flying normally.
  4. Only after the RF link is proven, enable WiFi Joystick and use the iOS app's Direct Radio Wi-Fi or Home Wi-Fi path.
OFFICIAL EXPRESSLRS WEB FLASHER →OFFICIAL TRANSMITTER UPDATE GUIDE →OFFICIAL WI-FI UPDATE GUIDE →OFFICIAL LUA SCRIPT GUIDE →OFFICIAL ELRS 3.4 RELEASE NOTES →OFFICIAL WI-FI JOYSTICK PROTOCOL →OFFICIAL EDGETX USB STORAGE GUIDE →