ExpressLRS is an open source RC link for RC applications. It is based on SX127x/SX1280 hardware combined with an ESP8285, ESP32 or STM32 for RX and TX respectively. ExpressLRS supports both 900 MHz and 2.4 GHz hardware options.
ExpressLRS can be flashed into existing Frsky R9M hardware (RX and TX) or custom PCBs can be make to suit. It can run at up to 500hz or down to 50hz depending on your preference of range or low latency.
At 900 MHz a maximum of 200 Hz packet rate is supported. At 2.4 GHz a blistering 500 Hz is currently supported with a custom openTX binary with plans to extend this to 1000 Hz once OpenTX support is added. This makes ExpressLRS one of the fastest RC links available while still offering long-range preformance.
ExpressLRS aims to achieve the best possible link preformance in both speed/latency and range. However, due to the optimized packet structure only basic telemetry is provided. If you want MavLink this project is not for you. ExpressLRS uses a compressed packet structure which priorities the first 4 control channels, this allows it to achieve better raw performance than other commercial solutions. ExpressLRS is also very affordable, a TX module can be built for $30 and receivers for $15-20. Likewise, new/second hand Frsky R9M gear is compatible and can be acquired inexpensively.
More information can be found in the wiki.
Links:
- Nano 2.4GHz RX Currently Smallest DIY 2.4Ghz RX
- 20x20 2.4GHz RX Convenient Stack Mounted DIY 2.4GHz RX
Links:
- Mini 900MHz RX Currently Smallest DIY 868/915MHz RX
- 20x20 900MHz RX Convenient Stack Mounted DIY 20x20mm 868/915MHz RX
Development is ongoing but the following hardware is currently compatible
| Brand | Type | Name | Notes |
|---|---|---|---|
| FrSky | TX | R9M | 2018 and 2019 versions, up to 2W |
| FrSky | TX | R9M Lite | output power 50mw in accordance with chip specification |
| TTGO | TX | LoRa v1 | not recommended due to bad RF design (~10mW) |
| TTGO | TX | LoRa v2 | power output 50mW |
| FrSky | RX | R9mm | |
| FrSky | RX | R9mini |
For the build you will need a TTGO LoRa board, with or without an OLED. These boards are readily available from ebay, aliexpress, and banggood. The only others parts required are some wire, 5 pin female header, and your favourite 5V regulator that can take the transmitters battery voltage range.
Note - The board I bought came with a female SMA pigtail. Check if your antenna is suitable.
V1 Hardware, (not recommended)
V2 Hardware
STLs for printing your own enclosure are available in the STL folder.
The use and operation of this type of device may require a license and some countries may forbid its use. It is entirely up to the end user to ensure compliance with local regulations. This is experimental software/hardware and there is no guarantee of stability or reliability. USE AT YOUR OWN RISK
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