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ExpressLRS is an open source RC link for RC aircraft. 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 250hz or down to 50hz depending on your prefererence of range or low latency.
At 900 MHz a maximum of 200 Hz packet rate is supported. This makes it the fastest long-range RC link currently on the market. Stick latency of down to 6.5ms is seen on firmware with crsfshot (aka openTX 2.4 mixer scheduler) support. At 2.4 GHz a blistering 250 Hz is supported with plans to extend this to 500 Hz once OpenTX support is added.
Due to the optimized packet structure only basic telemetry that gives up/downlink information is currently supported. Compared to commercial systems 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.
Now supports using easily available TTGO LoRa boards as TX modules for much easier assembly! Build information below.
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.
STLs for printing your own enclosure are available in the STL folder.
- Mini RX Currently Smallest DIY 900MHz RX
- 20x20 SX120 RX Convinient Stack Mounted DIY 2.4GHz RX
Building should be self explanatory given the schematic and BOM for each.
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.