1. Introduction
The HappyModel 2.4GHz ExpressLRS (ELRS) nano series receivers and the ES24TX Pro Micro ExpressLRS TX Module are open-source radio control components designed for FPV (First Person View) applications. Based on the ExpressLRS project, these modules offer low-latency and high-refresh-rate communication, making them ideal for FPV racing and long-range flights. Their ultra-light and nano-sized design also makes them highly suitable for tiny whoop drones.
2. Components Overview
This manual covers the following HappyModel ExpressLRS components:
- PP RX Receiver: Features an STM32L432KBU6 MCU and SX1280 RF chip with a built-in ceramic antenna.
- EP1 RX Receiver: Utilizes an ESP8285 MCU and SX1280 RF Module with an omnidirectional antenna.
- EP2 RX Receiver: Features an ESP8285 MCU and SX1280 RF Module with an SMD ceramic antenna.
- ES24TX Pro Micro ExpressLRS TX Module: An upgraded TX module with ESP32 (main) and ESP8285 (aux) MCUs, SX1281IMLTRT RF chip, and a Moxon antenna. It supports most OpenTX radio transmitters with a Micro JR bay.
- 2.4GHz Omnidirectional Antennas: Available in 40mm and 90mm lengths, compatible with IPEX/IPX/U.FL connectors.
3. Specifications
3.1 ELRS Receivers (PP RX, EP1 RX, EP2 RX)
| Feature | PP RX | EP1 RX | EP2 RX |
|---|---|---|---|
| MCU | STM32L432KBU6 | ESP8285 | ESP8285 |
| RF Chip | SX1280IMLTRT | SX1280IMLTRT | SX1280IMLTRT |
| Antenna | SMD Ceramic | Omnidirectional | SMD Ceramic |
| Dimension | 10mm*10mm*6mm | 10mm*10mm*3mm | 10mm*10mm*6mm |
| Weight | 0.47g | 0.42g (without antenna) | 0.44g |
| Firmware Target | 6cb8152d | aec8ad82 | aec8ad82 |
| Firmware Upload | Betaflight pass-through | Wifi | Wifi |
| Type | ISM | ISM | ISM |
| Frequency Range | 2400 MHz to 2500 MHz | 2400 MHz to 2500 MHz | 2400 MHz to 2500 MHz |
| Max Receive Refresh Rate | 500Hz | 500Hz | 500Hz |
| Min Receiver Refresh Rate | 25Hz | 25Hz | 25Hz |
| Working Voltage | 5v | 5v | 5v |
| Peak Gain | N/A | 2.23dB | 3.7dB |
3.2 ES24TX Pro Micro ExpressLRS TX Module
| Feature | Specification |
|---|---|
| Regulatory Domain | ISM2400 |
| MCU | ESP32 (main), ESP8285 (aux, as espbackpack) |
| RF Chip | SX1281IMLTRT |
| Socket | JR standard 5pin |
| Frequency Range | 2400 MHz to 2500 MHz |
| Maximum Receive Refresh Rate | 500Hz |
| Minimum Receiver Refresh Rate | 25Hz |
| RF Output Power | >30dBm |
| Power Supply Voltage | 5v~10v |
| Weight | 51g (without antenna) |
| Dimension | 70mm*49mm*32.5mm |
| Antenna Gain | 4.18dBi |
| Firmware Target | HappyModel_ES24TX_Pro_Series_2400_TX |
3.3 2.4GHz Omnidirectional Antenna
| Feature | Specification |
|---|---|
| Frequency | 2400.0 MHz |
| Efficiency | -0.89 dBi |
| Gain | 2.23 dBi |
| Efficiency (%) | 81.46 |
| Directivity | 5.12 dB |
| Peak Gain Position (Theta) | 180.00 |
| Peak Gain Position (Phi) | 330.00 |
| Efficiency ThetaPol (%) | 20.90 |
| Efficiency PhiPol (%) | 60.56 |
| Upper Hem. Efficiency (%) | 39.93 |
| Lower Hem. Efficiency (%) | 41.54 |
| Connector | IPEX/IPX/U.FL |
| Antenna Width | 52mm |
| Antenna Length | 40mm/90mm (optional) |
4. Setup and Binding Procedure
Follow these steps to bind your HappyModel ELRS receiver to your ES24TX Pro TX module or other compatible 2.4G ELRS TX:
- Enter Binding Mode (Receiver):
- Supply power to the PP/EP1/EP2 receiver.
- Wait until the LED on the receiver turns off.
- Immediately turn off the power.
- Repeat the above two steps.
- When the receiver is powered on for the third time, the LED light will start to double-flash, indicating that the receiver has entered binding mode.
- Bind from Transmitter (TX Module):
- Insert the ES24TX module (or other DIY 2.4G ELRS TX) into your radio transmitter's Micro JR bay.
- Choose 'External RF' mode and set it to 'CRSF protocol' in your radio's settings.
- Ensure the ELRS.LUA script is copied to your radio's SD-Card tools.
- Access the ELRS menu from your radio's system settings.
- Press the [Bind] option within the ELRS menu.
- If binding is successful, the LED on the receiver module will become solid.
4.1 Connection Diagrams
Proper wiring is crucial for the functionality of your receivers. Refer to the diagrams below for correct connections.
5. Operating Principles
The HappyModel ExpressLRS system operates on the 2.4GHz ISM band, providing a robust and reliable link for your RC models. The low-latency and high-refresh-rate capabilities ensure precise control and responsiveness, critical for FPV applications. Once bound, the system maintains a stable connection, indicated by a solid LED on the receiver.
6. Maintenance and Firmware Updates
The ExpressLRS firmware is continuously developed. It is recommended to keep your modules updated to the latest official firmware for optimal performance and new features.
- PP RX Firmware Upload: Firmware for the PP RX can be uploaded via Betaflight pass-through.
- EP1/EP2 RX Firmware Upload: EP1 and EP2 receivers support firmware upgrades via WiFi. When the receiver LED flashes fast, it indicates WiFi hotspot mode. Connect to the receiver's WiFi network and navigate to
10.0.0.1in a web browser (password:expresslrs) to upload new firmware. - ES24TX Pro TX Module Firmware: The ES24TX Pro module comes pre-assembled with a beta version of the firmware. Refer to the official ExpressLRS documentation for updating procedures for TX modules.
7. Troubleshooting
7.1 Receiver LED Status Meanings
- PP RX:
- LED solid: Bind successful or connection established.
- LED double-flash: In bind mode.
- LED flash slowly: No signal connection from the TX module.
- EP1/EP2 RX:
- LED solid: Bind successful or connection established.
- LED double-flash: In bind mode.
- LED flash slowly: No signal connection from the TX module.
- LED flash fast: In WiFi hotspot mode (ready for firmware upgrade).
8. User Tips
- Always ensure your receiver and transmitter firmware versions are compatible for best performance.
- For optimal range and signal quality, ensure antennas are mounted correctly and away from carbon fiber or metal obstructions.
- Regularly check the official ExpressLRS project website for the latest firmware releases and community support.
- When upgrading firmware via WiFi for EP1/EP2, ensure a stable power supply to the receiver to prevent interruption.
9. Warranty and Support
For warranty claims, technical support, or further assistance, please contact your retailer or the manufacturer directly. Keep your proof of purchase for any warranty-related inquiries. As these products are based on an open-source project (ExpressLRS), a vast community and extensive documentation are available online for troubleshooting and advanced configurations.
