The 7 onboard I/O of the Smartmotor will accept 0-5VDC... (at it's rawest resolution that is a 10bit analog value)... but the analog output device must be able to drive enough current to overcome the 5kOhm pull up resistor(tied up to the internal 5VDC regulator).
Using a 10K pot tied between pins 12(5VDC) and 13(GND) can also have some non-linearity. This is due to the pull up resistor. You may get better results if you tie the 0-5VDC signal(which can be 0-10VDC if you can limit it to 5VDC max)... with a 5kOhm pull down resistor tied to Pin13(GND) to balance the circuit.
With all that said... the analog option may work ok if you have enough resolvability with only 0-512 counts from your 0-10VDC analog output(even if it has 16bit resolution).
The best option is to use an analog device that can communicate or respond to/with an ASCII string to the Smartmotor... either using the RS232 or RS485 port. This gives you the best position resolution.
Please look at our Youtube videos. There is one using a Laser to detect distance that interfaces to the SmartMotor via RS485.