schem_aux_in

  1. This drawing uses a quad opamp from Texas Instruments to buffer and voltage scale as shown in the drawing.  Any opamp with Rail-Rail input and output can be used.
  2. The layout is not critical.   You should use a .1uf capacitor to bypass +5 to ground near the opamp package.
  3. You don’t have to use a quad opamp, you can interface to a single auxiliary channel with a single opamp, if desired.