PRX - Proximity Sensor Understanding

Hi all,

I was recently setting up two Benewake Rangefinders on my Arducopter using UART for both of the rangefinders. I have one mounted downwards and one forwards. I was able to successfully get the rangefinders working and measuring thanks to great documentation on the wiki pages. However, when I went to change the usage of the front facing rangefinder to a Proximity Sensor for simple obstacle avoidance, I couldn’t find much on how to tell which PRXx parameter to use. I set PRX1 to 4, and got it working, but how does Arducopter know which rangefinder is “1” or which is PRX2, or 3, etc in this case? It doesn’t seem to matter which of the two rangefinders is set as RNGFND1 and RNGFND2, does it have something to do with which rangefinder is first in the sequential listing of serial ports? I’d really appreciate any clarification on this scenario - thanks!