How to Setup TBS Crossfire and Tracer

TBS

TBS

This tutorial explains how to setup TBS Crossfire for OpenTX radios such as the TX16S. I will also show you how to connect Crossfire receiver to a flight controller and configure it in Betaflight. Tracer is similar to Crossfire when it comes to setup, so most of the steps in this guide also apply.

What’s TBS Crossfire?

TBS Crossfire is a popular radio control link for FPV drones, which is known to be reliable, easy to setup and great for long range flying.

Crossfire is an external RF module that can be installed directly on the back of a radio transmitter (i.e. JR module bay). The TBS Tango 2 radio also has Crossfire built in.

Rather than using the more common 2.4GHz,  Crossfire operates on the 900MHz band. The low frequency is better at signal penetration through obstacles. Many pilots prefer Crossfire even though they don’t intent to fly long range but for the stable link connection and resistance to failsafe in challenging environment. Range can largely depend on the conditions of the environment, but based on personal experience, I can fly 5 miles out easily using 250mW, and I wasn’t even pushing the limit there. One of the main downsides of Crossfire is perhaps the larger receiver antennas which can be challenging to mount on smaller FPV drones.

Installing Crossfire TX module in the Radio

You can install the Crossfire TX module directly in the external JR module bay on the back of the radio. Insert the module carefully, make sure all the pins go into the sockets of the Crossfire module properly.

 

The Crossfire module is fully compatible with radios with a JR module bay such as the Frsky Taranis X9D+, Jumper T18, T16, the RadioMaster TX16S and Radiomaster Boxer.

It also works with Taranis Q X7, and Horus X10S, but there are some minor issues due to these radios’ inability to operate at full baud rate, causing problems such as constant warning of “telemetry lost”. There is a DIY mod you can do to fix it, but it’s quite difficult to do (involves soldering to the main processor) and therefore I don’t recommend using these radios with Crossfire. Update: by flashing EdgeTX to these radios, you no longer need to do this hardware mod.

 

RX and FC Connection

Remember that almost all of the pins on the Crossfire receiver can be mapped in software. This means you can configure them to output whatever you want, and so there are more than 1 way to connect your RX to the flight controller.

The way I show you here is kind of the standard way that most people use, here are the connections:

  • 5V to 5V
  • GND to GND
  • CH1 (Crossfire RX) to UART RX (FC)
  • CH2 (Crossfire RX) to UART TX (FC)

You can use any spare UART on the flight controller.

You can also configure Crossfire receiver to output SBUS, this allows you to connect only CH1 to an RX pin on the FC, and leave CH2 unconnected. This is useful if you don’t have a TX pin on the FC, but CRSF is a better protocol than SBUS because it’s faster and also allows telemetry and that’s what I would recommend.

You must not use Soft Serial for Crossfire receiver because it’s not fast enough to handle CRSF signal.

In this example, I am connecting the Crossfire receiver to the UART 6 of the Kakute F4 AIO V2 FC.

Frequency

It’s important to make sure you are using the correct frequency depends on where you fly. You have two options, 868MHz and 915MHz, one of these frequency will be used by the cellular system, which you should avoid otherwise you will get interference from cellular system, causing dropouts and failsafe.

According to the Crossfire manual, the Blue and Purple regions should be using 915MHz while the Yellow region should be using 868MHz. For example, US should be using 915MHz while Europe should be using 868MHz.

Here are the different frequency options. Only use the Race frequencies if you are actually racing as they sacrifice range for bandwidth for more consistent data packets. LBT means “listen before talk”.

Region and frequency are not available for Tracer as it’s on 2.4GHz which the same frequency band worldwide.

Max Power

Higher output power means more range, but you don’t always want to run at max output power.

Firstly, higher output power drains the battery faster. Secondly if you fly with other people (especially if you are all using Crossfire or other 900MHz systems), it can interfere with other pilots and cause signal dropouts and failsafe if all are using max output power. For short distance (such as racing), it’s probably a good idea to use 25mW.

For a typical FPV drone setup, setting power to around 250mW is adequate in most situations, which can give you miles of range in line of sight.

Dyn. Power

The dynamic output power option can help mitigate some of the problems mentioned with maximum output power. It dynamically adjusts the output power depending on signal strength. Beware that as soon as you unplug the quad, the transmitter will automatically go to maximum output power, which is not a good idea when you fly with other people who are also using Crossfire.

In Tracer, you have 25mW, 100mW and Ludicrous which is about 1W. Because Tracer doesn’t have as much range as Crossfire most people would just run Ludicrous with Dynamic power enabled so it brings the power down when you are flying nearby.

Receiver Mode

There’s one more settings you want to change, which is “Mode” in Receiver settings. You can only access receiver option when you have your receiver bound to the transmitter and powered on. These options are saved per receiver, so you have to set these for every quad you have.

Mode is the number of channels you want to use, you have two options, 8 Ch and 12 Ch.

Just select 12 channels.

You will get four more channels to use. Maybe you don’t need them, but 8Ch mode and 12Ch modes have basically no difference in terms of performance, the extra 4 channels will come in handy when you need them.

However for fixed wings if you want all channels to have full resolution, you should leave it at 8Ch instead. But for multirotor it’s fine to use 12ch.

Make sure telemetry is on, and set Failsafe to Cut so that the motors stop spinning in the event of signal loss, and your quad will drop out of the sky to minimize damage.

RF Profile

You can select which packet rate you want to run, options are 50Hz, 150Hz or Dynamic.

It depends on if you want lower latency or long distance. 50Hz will have higher latency but gives you way more range because it has higher receiver sensitivity and also uses LORA modulation while 150Hz has lower latency but less range.

You can set it to dynamic, it will shift to the lower latency as your signal gets weaker. However Betaflight devs actually don’t recommend using Dynamic due to RC signal smoothing in the FC firmware which is tied to a fixed packet rate value, it won’t work properly with dynamically changing packet rate. If you fly long range, lock it to 50Hz, if you do racing or just in close range, 150Hz should be fine.

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