APM 2.8 FrSky L9R RSSI

I’m having bit of trouble getting RSSI to work. I’m using Mission Planner 1.3.56 and Plane 3.4.0. In 3.4.0 all I have to configure is RSSI_Range and RSSI_PIN. I have RSSI_Range set to 3.3. It doesn’t matter what I set RSSI_PIN to I get rssi: 160 in the “Flight Data” window. It bounces around some some, maybe 145 to 165 (this would be close to it reading 5v) I’m really not sure what to set RSSI_PIN to or where to connect the RSSI out from the L9R. I know I’m missing something simple be it has eluded me all afternoon. Thank for taking the time to read.