RadioMaster XR2 Receiver User Manual

Product Overview

This document provides detailed information for the RadioMaster XR2 Nano 2.4GHz ExpressLRS Receiver. The receiver is designed for radio control applications, utilizing the ExpressLRS (ELRS) protocol.

The XR2 Nano receiver features a compact design with integrated antenna, powered by an ESP32C3 MCU and Semtech LR1121 RF chip.

Physical Description

The receiver is approximately 16mm in length, 12mm in width, and 6mm in height, weighing only 0.8g. It features a ceramic antenna and connection pins for power (5V), telemetry (TX), and receiver (RX) signals, compatible with CRSF and UART interfaces. Key components visible on the board include the ESP32-C3 microcontroller (marked 322024) and the LR1121 RF chip (marked 2419 480309). A BIND pin is also present for binding procedures.

Specifications

Item	XR2 Nano 2.4GHz ExpressLRS Receiver
Type	ISM2.4
MCU	ESP32C3
RF Chip	Semtech LR1121
Antenna	Integrated 2.4GHz Tower Antenna
Frequency Range	2.400 - 2.479GHz
Telemetry Power	10mW
Maximum Packet rate	DK500Hz
Minimum Packet refresh rate	50Hz
Working voltage	5V
Weight	0.8g
Dimension	16mm * 12mm * 6mm
Firmware Version	ExpressLRS v3.5.1 pre-installed
Bus interface 1	CRSF
Bus interface 2	UART

Includes

1 * XR2 Nano 2.4GHz ExpressLRS Receiver
1 * CRSF Wire
3 * Heat-Shrinkable Tube
1 * Manual Card

Default Firmware

The default firmware is RadioMaster XR2 2.4 RX.

For more information, please visit the ELRS website: https://www.expresslrs.org/2.0/

Configuration

To configure the receiver, follow these steps using Betaflight Configurator:

Open Betaflight Configurator.
Navigate to the
Ports
tab.
Enable the corresponding UART for the receiver as a
Serial RX
(e.g., UART2 as shown in diagrams).
Save and restart the configurator.

In the Configuration tab:

Under the Receiver section, select
Serial-based receiver
.
Choose
CRSF
as the Serial Receiver Provider.

Ensure the UART selected for the receiver is set to 'Serial Rx' in the Ports tab.

Traditional Binding

Follow these steps for traditional binding:

Power OFF your transmitter/radio.
Plug in and unplug your receiver three times.
Verify the receiver's LED is performing a quick double blink, indicating it is in bind mode.
Power ON your transmitter/radio and use the
[BIND]
button on the ExpressLRS Lua script to send a binding pulse.
The receiver is successfully bound when its LED shows a solid light.

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