Solid on
Connected to a transmitter, or bootloader mode
- Cause
- Normal connection; bootloader is also possible on single-colour receivers
- Fix
- Confirm the ExpressLRS Lua script shows C and verify stick movement before flight.
Free guide
Binding ELRS, and what the LED means
Binding is where new builders stall. The radio says one thing, the receiver blinks something else, and nothing in either manual connects the two. This is the whole procedure, plus the decoder for every LED pattern you are likely to see.
What this covers
- Radios
- RadioMaster Boxer and Pocket
- Firmware
- ExpressLRS 4.1.x
- Receivers
- RP1, RP2, RP4TD, EP1, EP2, BETAFPV Nano
- Configurator
- Betaflight App / firmware 2025.12.x or newer
Print the one-page sheet (PDF)
Version numbers matter here more than almost anywhere else in FPV. A radio on the reviewed ExpressLRS 4.1.x baseline will not bind to a receiver still on a different major version such as 3.x. Keep both on major 4; the symptom is a blink pattern rather than an error message.
The receiver LED decoder
Find your blink pattern. Almost every bind problem is one of these.
Slow blink (500 ms on/off)
Waiting for connection from the transmitter
- Cause
- Radio off, incompatible major versions, bind phrase mismatch, or link not established
- Fix
- Power the radio, then verify the major versions and bind phrase match.
Fast blink (25 ms on/off)
WiFi mode enabled
- Cause
- Receiver entered WiFi update mode
- Fix
- Use the WebUI if updating; otherwise reboot and reconnect to the transmitter.
Double blink, then pause
Binding mode enabled
- Cause
- Receiver was deliberately put into traditional bind mode
- Fix
- Press Bind in the ExpressLRS Lua script, or reboot to cancel bind mode.
Triple blink, then pause
Connected, but Model Match configuration does not match
- Cause
- The receiver's Model Match ID differs from the active radio model's Receiver ID
- Fix
- Correct or disable Model Match while the transmitter and receiver are connected.
Medium blink (100 ms on/off)
Radio chip not detected
- Cause
- Receiver hardware or firmware cannot communicate with its RF chip
- Fix
- Reboot once, then check the exact target and the receiver manufacturer's support guidance.
Off, no LED
No power
- Cause
- Wiring fault, blown receiver, or reversed polarity
- Fix
- Check for 5 V on the receiver pads. Continuity meter first, then look at the joint.
Brief flicker
Power cycling
- Cause
- Brown-out or poor wiring under load
- Fix
- Check pack voltage and the FC's BEC output. Rework a joint only if inspection or measurement shows poor wetting, cracking, movement, or another defect; a uniformly dull SAC305 surface alone is not a fault.
Anything else
Hardware-specific status
- Cause
- Vendor-specific pattern
- Fix
- Check the manufacturer's datasheet. Most elaborate patterns are vendor status codes.
Set the radio up first
Create the model
System → MODEL → Create model. Pick the template "Multirotor — ELRS", then confirm on the model select screen.
Name it
Page right to MODEL SETUP. Set a name you will recognise three months later — "5inch-2026" beats "model 03". Model number and image are optional.
Internal module → CRSF
MODEL SETUP → Internal RF. Type: CRSF. This is the moment the radio's internal ELRS module wakes up; channel ranges populate automatically.
Bind phrase
With ExpressLRS 4.1 and a compatible Lua tool, set the bind phrase on the transmitter and on a connected receiver directly from the handset. Flashing options and each device's WebUI remain supported alternatives. ExpressLRS recommends at least eight alphanumeric characters. Write it down somewhere that is not the radio.
Packet rate
Tools → ExpressLRS → Packet Rate. 250 Hz for indoor whoops and 5-inch freestyle (the default), 500 Hz for racing, 100 Hz for long range. Higher rate means lower latency and less range.
Save and exit
Long-press EXIT to return to the model screen. Power on the intended receiver and confirm the Lua script shows C before testing stick movement.
The bind phrase. The bind phrase lives on the radio AND on the receiver, and both must match: same string, exactly, case-sensitive, no trailing spaces.
Bind the receiver
Preferred — bind phrase
- On 4.1, use a compatible Lua tool to set the same phrase on the transmitter and a connected receiver directly from the handset where supported. You can alternatively set it while flashing or in each device's WebUI. The Lua Bind command is for traditional binding; it is not needed for devices sharing a bind phrase.
- Power on the radio, then power on the receiver.
- A slow blink means the receiver is waiting for the transmitter. Solid means it connected; also confirm the ExpressLRS Lua script shows C.
Fallback — traditional binding
- Traditional binding requires the receiver to have no bind phrase set. Power-cycle it three times: apply power, remove it within two seconds, and repeat twice more. Supported receivers can also enter bind mode from Betaflight's Receiver tab / `bind_rx`, or by a 1.5-second receiver-button press.
- Confirm the receiver shows a double blink followed by a pause.
- Power on the radio and press Bind in the ExpressLRS Lua script.
- When the binding pulse reaches the receiver, the LED changes to solid.
Verify in Betaflight
- Power the flight controller over USB, open Configurator and connect.
- Open the Receiver tab and confirm Serial Provider is CRSF.
- Power the FC from a pack — props off, on the bench — so the receiver wakes.
- Move the sticks. The channel bars should move with them.
- If they do not move, work the LED decoder below.
Model match. Model match is optional and off by default. Turned on, the receiver only listens to the radio's currently selected model, which is useful once you fly several quads. EdgeTX → Tools → ExpressLRS → Model Match.
The AUX channel map the book recommends
| Channel | Mode | Switch | Active range |
|---|---|---|---|
| AUX1 (ch 5) | ARM | SA (2-position) | 1700–2100 |
| AUX2 (ch 6) | ANGLE5-inch optional | SB (2-position) | 1700–2100 |
| AUX3 (ch 7) | PREARM | Momentary trim or button | 1700–2100 |
| AUX4 (ch 8) | BEEPER | SC (2-position) | 1700–2100 |
| AUX5 (ch 9) | BLACKBOX | SD (3-position, top) | 1700–2100 |
| AUX6 (ch 10) | GPS RESCUE5-inch only | SD (3-position, middle) | 1300–1700 |
| AUX7 (ch 11) | FLIP / TURTLE | SE (2-position) | 1700–2100 |
| AUX8 (ch 12) | Spare / reserved | — | — |
The book is opinionated, not religious. If your hand prefers ARM on SB and BEEPER on SA, run the swap and set the aux lines to match. The pattern that matters is deliberate switches with ranges that never overlap.