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Preparing your Radio


Radio Firmware with CRSFShot/Mixer Sync

ExpressLRS requires CRSFShot or Mixer Sync to ensure full support for high packet rates. Starting with OpenTX-2.3.12, CRSFshot has been fully implemented, and thus you will have to update your OpenTX radio to these newer versions.

Another alternative is EdgeTX, the bleeding edge fork of OpenTX.

These firmwares allow flashing of .elrs files too.

CRSF Protocol

ExpressLRS uses the CRSF serial protocol to communicate between the transmitter and the TX module. To set this up, enter into your model settings, and on the "Model Setup" tab, enable your "External RF" and select "CRSF" as the protocol:

NOTE: Make sure the internal module is turned off.


NOTE: Make sure the internal module is turned off.

Serial Baud Rate

On some transmitters, the baud rate for comms between the opentx and the ExpressLRS module can be changed. The two rates available are 115200 and 400000. ExpressLRS supports both rates (auto switches to the correct rate on power-up), however, we have found that on the R9M 2018 modules, the inverter IC's that are used are not capable of reliably handling 400k baud. If you're using an R9M 2018 module, select 115200 baud in OpenTX, or do the resistor mod described on the R9M 2018 Resistor Mod page.

The QX7, X10/S, X12 will also going to require the Crossfire Mod if you're going to use 400k baud rates for use with higher packet rates, particularly with the 2.4G ExpressLRS Modules. Alternatively, EdgeTX can be flashed into these Radios and have OneBit enabled.

The X9D(plus) can't change its Max Bauds settings, but it has been found to be finicky, causing unstable packet transfers, and constant Telemetry Lost/Recovered messages from OpenTX. One fix for this is the use of the OneBit firmware or EdgeTX. Click here for more info.

Baud Rate

ADC Filter

The ADC filter is enabled by default in OpenTX and is known to cause issues with RC Command data. This can result in "jagged" RC command responses in black box logs, caused by sequential RC packets that have the same command value (which were "smoothed" by the ADC filter). We recommend turning the ADC filter OFF in OpenTX.

Now that your radio is set, you can now proceed with flashing ExpressLRS!