SRXL connection with PX4 firmware

Hi all! I am using PX4 firmware v 1.10.1 and am trying to increase the channels on my AR7700 receiver to 12, instead of just 8 using ppm. I have been trying to get the SRXL connection with my Pixhawk 1, however it is not working (I have not control). Is there a change I need to make in the firmware to make SRXL and PX4 compatible (or remote receiver, just anything to increase the channels). Thank you!