FrSky sells 2 small Taranis compatible receivers: X4R and X4RSB. By default, they offer only PWM signal. 4 channels on X4R and 3 channels plus S.Bus (16 channels over S.Bus) on X4RSB. And that is problematic. Many flight controllers does not support S.Bus very well (no inverters) or just does not offer enough UART ports. When speaking of small multirotors, PPM signal is often the best choice. That made X4R almost useless. For X4RSB additional S.Bus-PPM conversion cable had to be used.
Luckily, this has changed, since FrSky started offering custom X4R/X4RSB firmware that allows 8 channel PPM signal on receivers port 1. The only thing you have to do is to flash you receiver. And those are the steps to do it:
- Download CPPM firmware from this site. Remember that you need proper EU/non-EU version. It all depends if your Taranis and it’s built in XJT module has EU or non-EU firmware. How to determine EU/non-EU Taranis? If you are living outside EU you probably have non-EU firmware. If you are living in EU but bought from non-EU country (China probably) you have non-EU. Also, if in menu you can select D8 or LR12 internal radio mode, you have non-EU firmware. EU firmware allows only D16 mode,
- Follow those steps to flash X4R/X4RSB using Taranis built in port,
- Put a jumper on signal pins 2 and 3,
- Bind receiver with Taranis,
- Remove jumper.
From now on, pin 1 outputs PPM channels 1-8, pin 2 outputs PWM CH9, pin 3 outputs PWM CH 10, and pin 4 outputs either PWM CH11 in X4R or S.Bus on X4RSB. If you want to go back to non-PPM mode, bind receiver again, without jumper on pins 2 and 3.