FAQ

ExpressLRS is a high-performance, open-source radio control protocol built from the ground up to be an extremely fast (Express), extremely sensitive (Long Range) System. ELRS uses Semtech SX12xx LoRa transceivers and a lightweight, highly optimized over-the-air (OTA) protocol to provide superior performance compared to legacy RC links. While ExpressLRS started with DIY and repurposed hardware, a large number of manufacturers are now producing high-quality, low-cost transmitters and receivers to make it easy for anyone to get started!

ExpressLRS is capable of extremely high packet rates (up to 1000 Hz) and extreme sensitivity (ranges well over 100+ km have been achieved with 2.4 GHz hardware), making it extremely competitive with any commercially available system. And since ExpressLRS is open-source, it costs much less than other systems too!

ExpressLRS requires OpenTX 2.3.12 or newer, as it depends on CRSFShot (a.k.a mixer sync) to work properly. However, as OpenTX is no longer being maintained, it is strongly recommended that you update to EdgeTX in order to take advantage of the latest performance improvements and bug fixes.

Click here to read more about radio firmware requirements and setup.

See Getting Started for a Quick Setup guide and detailed instructions on flashing, features, hardware, and troubleshooting.

Any Receiver and TX Module from the same Band (e.g. 2.4 GHz or 900 MHz) will work together. For example, a 900 MHz receiver from BetaFPV will work with a 900 MHz TX module from HappyModel. Likewise, any 2.4 GHz receiver will work with any 2.4 GHz TX Modules, from any manufacturer (including DIY ones). This of course assumes the hardware is working properly, flashed with the same major ELRS version (e.g. 3.x), and is using the same binding phrase and configuration options (e.g. Regulatory Domain).

Early ELRS receivers like the HappyModel PP used an STM32 MCU, while later designs EP1/EP2/etc use ESP MCUs. All offer firmware updates via UART or Betaflight Passthrough, but the ESP-based hardware also support firmware update and configuration over WiFi. The EP1/RP1 receivers use u.fl (external) antennas, while the EP2/RP2 receivers use on-board ceramic antennas. Receivers like the RP3 and R24D have two antennas for antenna diversity, while receivers like the EP1 Dual, RP4TD, and SuperD add a second parallel RF path to provide full receiver diversity.

See here for more about different antenna configurations.

In order to achieve the fastest packet rate, your radio must be running a supported firmware, set to a minimum hardware baud rate of 921000, and be connected to a serial ELRS receiver (SPI receivers do not support the FLRC modes required). Also make absolutely sure ADC filter is disabled on your radio, and that you have applied the appropriate RC Link Preset in Betaflight.

You can use the ELRS lua to check your current packet rate and ensure the radio mixer sync is working properly. See Using the Lua Script for more details.

ELRS supports up to 16 channels*. Channels 1-4 are always sent at full-resolution (10-bit). The resolution and update rate of the remaining channels can be configured as follows, based on your requirements:

• 4x full-resolution (10-bit) channels for sticks (CH1-4) with either:
  • HYBRID Mode 1x 2-position channel, AUX1 (CH5; Must be used for Arming), 6x 2-position/3-position/6-position (AUX2-7) and 1x 16-position (AUX8), OR
  • WIDE Mode 1x 2-position channel, AUX1 (CH5; Must be used for Arming), 7x 64 or 128-position channels (AUX2-8). Available via the Lua Script since 2.0.
• 8x full-resolution (10-bit, ext-limits) with 1x 2-position channel, AUX1
• 16x full-resolution (10-bit, ext-limits, all half rate) with 1x 2-position channel, AUX1
• 12x full-resolution (10-bit, ext-limits) with 1x 2-position channel, AUX1, channels AUX2-9 run at half rate.

See Switch Modes for more details on switch modes and how they work.

No, just like what channel your VTX is on is not a secret. If everyone kept their VTX channel a secret, the chances of you blasting someone out of the sky accidentally is high. The binding phrase is not used for security, it is used to prevent collisions. Specifically, the binding phrase is hashed and used to seed the random number generator that determines the frequency hopping pattern. Thus, each binding phrase results in a unique hopping pattern, minimizing the likelihood of collisions with other users. To provide the best chance of not interfering with other pilots and them not interfering with you, be sure you're not using the same dumb bind phrase as someone else. Express your style with a hilarious or saucy bind phrase.

See the Signal Health page for more info on interpreting link stats.