If you have a pixhawk then no more cabling is required as the receiver will be sending all the rc channels to the pixhawk through ppm. If you have an apm then yes, you will need to connect the receiver’s channel 8 to the apm’s channel 8 input.
Then, if you set -
Then look in the HUD on mission planner and choose the status tab, you can see what the channel 8 value goes to with the transmitter on and off.
Then you set
RSSI_CHAN_HIGH, to the pwm at 100% rssi
RSSI_CHAN_LOW, to the pwm at 0% rssi
Obviously this is only valid for plane v3.4
As far as I’m aware that should work, only used the analog pin from my d8r.