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OpenRX Gemini — front
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File 03 · ELRS Receiver

An ExpressLRS receiver, open from antenna to firmware.

Four board designs, one firmware. Lite runs SX1281 on 2.4 GHz with a ceramic antenna. Lite-UFL swaps to a U.FL pigtail. Mono steps up to a single LR1121 for multi-band. Gemini runs dual LR1121 in ExpressLRS Xrossband mode for frequency-diverse links.

Model· pick your build

€39.00
SKU OPENRX-GEMINIincl. VAT · excl. shipping
In stock · ships from Belgium
01Teardown

One ESP32-C3, one (or two) radios, careful RF.

Every variant runs on the ESP32-C3 at the MCU layer. Lite uses Semtech SX1281 with the 2450FM07D0034 BPF; Mono and Gemini use Semtech LR1121 with the RFX2401C + SKY13373 + Johanson IPD front-end. Firmware targets upstream to ExpressLRS (Unified_ESP32C3_2400_RX for Lite, Unified_ESP32C3_LR1121_RX for Mono/Gemini).

  • ①ESP32-C3, Wi-Fi OTA + CRSF
  • ②SX1281 (Lite) or LR1121 (Mono/Gemini)
  • ③RFX2401C + SKY13373 front-end (Mono/Gemini)
  • ④U.FL or ceramic antenna
02Open for learning

Published so you can study it. Produced so you don't have to.

Study

GitHub repo ↗

Schematic · PCB · BOM · 3D STEP · design notes

Iterate

Open issues ↗

Rev candidates · bugs · community discussion

License

CERN-OHL-S v2 ↗

Strong reciprocal: share your changes

Last commit · OpenRX

updated HW files as ordered

cab939fBastian13 h ago

03In the box

Everything that ships, down to the grommet.

Here is the actual parts list. Anything missing from a build, say so and we'll ship it.

  • 1×OpenRX boardtier selected at checkout
  • 1×CRSF servo cable3-pin JST-SH1.0, pre-crimped, 10 cm
  • 1×Heat-shrink sleeve + double-sided tape
  • 1×Build cardbatch ID, QC initials, ExpressLRS flash target, GitHub rev
  • 2×U.FL dipole antennadiversity pair

Provenance

  • DesignedLeuven, Belgium · schematic, PCB, BOM, firmware partnerships
  • AssembledShenzhen, China · first runs, while we bring up an EU line
  • NextEU assembly · in planning
04The €1

What you pay, what the people who wrote the firmware get.

€38.00
€1.00
€39.00

€38 for the board.
€1 for the ExpressLRS ↗ maintainers.

05Datasheet

Every spec, in one table.

Firmware
ExpressLRS (3.5.0+)
Telemetry
CRSF
MCU
ESP32-C3, 4 MB flash
Wi-Fi antenna
Dedicated on-board ceramic, separate from the link antenna
Flashing
UART with on-board BOOT button, Wi-Fi OTA, BF passthrough
License
CERN-OHL-S-2.0
Radio
2× Semtech LR1121, two complete radio chains
Flash target
Unified_ESP32C3_LR1121_RX
Telemetry power
12–22 dBm per radio (~158 mW), 12 dB RX LNA per chain
Antenna
2× U.FL, one per radio
Size
17.05 × 15.75 mm, 6-layer

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