ExpressLRS backpack and ELRS options from your phone

ExpressLRS has two kinds of backpack. A TX backpack is an ESP chip on or next to the transmitter module; many modules have one built in. A VRx backpack sits in the video side: inside HDZero goggles, or wired to a module such as SkyZone SteadyView, ImmersionRC RapidFIRE or another supported video receiver. Paired by the same binding phrase, the two talk over ESP-NOW, so the radio can change the video channel, start DVR recording from a switch and pass telemetry on, without a cable between them.

There are also backpacks for antenna trackers and race timers, each with its own hotspot. FlySpark recognises the TX, VRx, Timer and AAT backpack hotspots, and on a VRx backpack it reads which receiver the firmware was built for: HDZero, SteadyView, SkyZone, RapidFIRE, Fusion or Orqa.

Turn on the Wi-Fi of the device you want. On a TX module, open the ExpressLRS Lua script on the radio and choose WiFi Connectivity, then Enable WiFi for the module or Enable Backpack WiFi for its backpack. A receiver starts its own hotspot after a while without a link. HDZero goggles start their backpack Wi-Fi from the goggles' own menu.

Join the hotspot (the password is expresslrs) and connect to 10.0.0.1. On Android, the quickest route is the ExpressLRS tool: it searches for any 'ExpressLRS …' hotspot, joins it, and when it finds a backpack its FlySpark view opens this page. If the device is already on your home Wi-Fi, keep the phone on the same network and tap the matching .local chip instead.

When it connects, the device card shows the product name, whether it is a TX module, receiver or backpack, the firmware version and target, whether Wi-Fi is on its own hotspot or your home network, and the binding UID in use.

Since ExpressLRS 3.0, many choices that used to be build flags live in an options file on the device. FlySpark reads that file, shows the options this firmware has, and writes it back with only your changes. Wi-Fi turns on after sets how many seconds without a link pass before the hotspot starts, or -1 for never. A home Wi-Fi name and password let the device join your network instead of starting a hotspot. On 900 MHz hardware you can pick the regulatory domain: AU915, FCC915, EU868, IN866, AU433, EU433, US433 or US433 wide.

A TX module adds unlock higher power (where the firmware still has it), the telemetry report interval and the fan's minimum runtime. A receiver adds its UART baud rate, which must match the flight controller (420000 for CRSF by default), and lock on first connection, which keeps the receiver on the packet rate it first links at. Saving reboots the device; its Wi-Fi turns off as it restarts.

Each TX module has a hardware file from its maker that sets which output powers it may use. FlySpark shows the four limits from that file, minimum, default, high (the level that needs unlock) and maximum, and refuses to save if they are out of order. These are ceilings, not the power you fly with. Choose everyday power and dynamic power in the ELRS Lua menu or on the radio.

Raising a limit above what the amplifier is built for can overheat or damage the module, and may break your local radio rules, so FlySpark asks you to confirm before it saves and reboots.