The circuit will be used in a test console.
The unit under test have 2 analog inputs and supply 5v to the joystick.
By trying to keep it simple I went for an game console joystick, a single spring loaded potmeter .
In center position the 2 analog inputs to the unit needs 2.5V each
When joystick is moved, the unit perform a calculation on the 2 analog inputs, the sum of the 2 analog channels must be 5V
Example: If potmeter output is 1.5V
OUT1 = 1.5V
OUT2 = 3.5V
If the 2 values calculated together, is not 5V, the unit gives an fault.