With my leg project, I will use absolute encoder instead of potentiometers. During my research, I've found an interesting "cheap" encoder from CUI. The AMT-203. Arduino can "speak" with it by the use of the SPI bus.

I've found a sample code which is working for me. 

It comes from the arduino forum :

Hi,

I'm having trouble to get my PS3 controller working as I want to.

My idea is to move the head when using the left stick.

Joypad is connected, it is detected and everything seems to work.

I want to move the head as long the stick is oblique.

This is the code (simplified withou servo, just prints):

April 6, 2018.

  Fred-X's middle is finished... Sort of.

I have completed the mechanical assembly.  I have discovered that if I change the state of configuration file 9 Neopixel from False to True that it causes the software to run as though there were some process eating up 99 % of the system resources. 

  I recommend not trying to run a NeoPixel ring unless you have a fix for this. I am not at that point yet.

  As soon as I get Fred's right leg finished I eill be standing him on his own legs.