How to enable 16-channel RC mapping

I am using Pixhawk MINI with FrSky X8R + FrSky Taranis X9D. I enabled 16-channel (D16) on Taranis X9D and I connected the X8R to pixhawk mini through SBUS and SBUS to CPPM.

In qGroundControl I changed RC_CHAN_CNT from 8 to 16, and in the firmware code src/modules/px4iofirmware/px4io.h, I changed the parameter PX4IO_RC_MAPPED_CONTROL_CHANNELS from 8 to 16.

I thought this would enable 16-channel RC communication and mapping, however it did not work and I am still getting 8 channel reading, both in the Qgroundcontrol interface, and by directly accessing system console and listening to topic name input_rc.

I am wondering does PX4 support 16 channel rc mapping? Because I found that seems I am not supposed to change the PX4IO_RC_MAPPED_CONTROL_CHANNELS value.

If PX4 does support 16 channel RC, how should I configure it correctly?

You have to put jumpers on the 1 & 2 and 3 & 4 signal pins of the X8R before binding to the X9D. Download the X8R Manual if you don’t have one.

Good luck.