In this article, we will look at the differences between FrSky EU & Non-EU firmware and how it affects you and your craft. If you are familiar with FrSky and its products and have been flying or using their radio transmitters, you may have come across the term FCC or EU_LBT while flashing new firmware on the transmitter.


What is a firmware?

Firmware is the piece of code or program that runs on your transmitter radios and receivers. It is what enables the transmitter and receiver to “talk” to each other. Each manufacturer uses their own firmware for their products. FrSky’s internal (and external modules) XJT module uses two types firmware - FrSky EU & Non-EU (LBT).


What kind of firmware are there?


That is a great question! Your devices have differents part in the whole system - The transmitter radio controller, its transmission module and the receiver. Each of these three systems uses different firmware since each of them has a different purpose in the system.


Transmitter radio controller firmware - FrOS or OpenTX (Like the X9D uses OpenTX 2.3)

Transmitter module (XJT module) - FCC or LBT (Also called FrSky EU & Non-EU firmware)

Receiver module - Here too, FCC or LBT (Also called FrSky EU & Non-EU firmware)


Though both the XJT module and receiver have FCC or LBT type of firmware, it is important to note that they are not interchangeable - you can not use the XJT FCC or LBT (FrSky EU & Non-EU) firmware on the receiver or vice versa on the XJT module.


Why two different firmware?

You might be wondering why there are two types of firmware - FrSky EU & Non-EU for the transmitter module and the receiver.


The answer is simple - Local Regulations & Laws ;)


As you might know, each country has its own local regulations regarding the usage of radio transmitters and frequencies it occupies and these regulations make it difficult for manufacturers to have a universal firmware that works and is legal in all countries.

Enter FrSky EU & Non-EU firmware. These have been designed to tackle this issue right at its core - frequency hopping pattern.



FrSky EU & Non-EU firmware differences


The Non-EU firmware or the FCC firmware from FrSky is what is used worldwide except in the EU region because the laws are more strict in the EU.


ACCEST Protocol


The ACCST protocol from FrSky uses a “frequency hopping” technique to transmit the data from the transmitter to the receiver and the telemetry data the other way. The protocol allows the transmitter and receiver to transmit on a particular frequency - say ‘n’ and then move to the next available frequency - say ‘n+1’. If the data has not to be received at the reception side, the device jumps to the next frequency - ‘n+2’ and so on. The FrSky EU & Non-EU firmware has a similar working principle


The transmission on a single frequency last only a small amount of time and this ensures that many users can operate in the same frequency bands without having interference with each other.


Non-EU (FCC) Firmware


Now, this is fine in the FCC version as the frequencies spectrum allotted for the transmission is already in the spectrum of 2.4GHz is already certified by the manufacturer - FrSky in this case and is up to the user to use the transmitter without legal issues.


EU (LBT) firmware


In the case of the EU, there are few frequencies that aren’t legal to transmit on. To tackle this, the transmitter has to ‘Listen Before Talk’ or LBT. This basically means that the transmitter has to check the frequency it’s about to transmit on and is only allowed to transmit if no other transmission is occurring in that particular frequency at the time of transmission.



Which firmware should I use between FrSky EU & Non-EU?


I feel the answer to this question is obvious - choose EU (LBT) firmware if you are using it in the EU region or use the Non-EU (FCC) version if you are using it anywhere else.

Just make sure both your transmitter module (XJT) and your receiver both have the same firmware - FrSky EU & Non-EU.


It is also to be noted that the FrSky EU version will NOT support the D8 protocol in case you want to use it with micro quads like whoops with an in-built receiver.




In this article, we have discussed what firmware and protocols are and how the FrSky EU & Non-EU differ and which one to use for your radio. Hopefully, with this article, you now have an idea about the ACCST protocol and how the frequency hopping system works.