How to Bind with External ExpressLRS Receiver

1. Power on and power off the receiver or FC continuously three times.

2. The indicator light of the receiver blinks twice as a cycle, which means that the receiver has entered the binding mode. The indicator light of the receiver is shown below.

3.  Using the remote controller or TX module to send the binding signal. If using the BETAFPV Nano TX module, with stock firmware (RC5 version), press the TX module binding button once to enter the binding mode. With major release 1.0.0 version or above, press the button three times to enter the binding mode. Besides, the Nano TX module could enter binding status via the ELRS Lua script.

4. The indicator light of the receiver is solid, which means binding success.

The firmware version of the receiver and TX module must be consistent before binding,  the factory default firmware version of the receiver is RC 0.5, which cannot be bound with TX module with firmware version of RC 1.0 or above. If binding is required, the receiver firmware needs to be upgraded. 

How to Bind (Binding Phrase)

If your receiver and TX module have set the same binding phrase from the ELRS configurator, the binding steps as shown below：

If the binding phrase is used, the receiver cannot enter the binding state through three consecutive power-on, you only need to power on the TX module and the receiver with the same phrase, they will bind automatically. This is available for both the RC5 version and the 1.0.0 version.

The binding steps for the ELRS receiver integrated on FC are the same as above.

You could learn more details from this.