Klen,
Actually USB joystick with pots use this as voltage divider: vary voltage from 0 to 5 volts (some, like entry level Saitek and Logitec vary from 0 to 3,5 volts).
HALL sensor work in the same way, vary the voltage from 0 to 5 volts when a magnetic field change in front them.
Like Recoilfix say, HALL like Alegro A1302 come whit 3 prongs - but pay attention in HALL .PDF for where prongs go.
Potentiometers prongs typically are:
+5V - Signal - Gnd (if you need invert response change wires between +5 and Gnd).
Alegro A1302 use this arrange - front view (BTW search for A1321 that is more sensible):
+5V - Gnd - Signal (If you need invert response just turn magnets 180 degrees).
The major difficulty in this assemble is find correct alignment between HALL and magnets, due small size o HALL ~ 3 x 4 x 2 mm.
Basic setup:
But this assemble is flexible, you can place HALL in front magnet, between two magnets (ie around Bic pen tube), inside a circular magnet...
Sample o pot convert to HALL:
Note - If stick circuit aliment pots with +5V volts, you just solder pots wires in HALL (accord HALL .PDF).
If stick circuit only proven 3,5 v to pots (Saitek EVO, Logitech 3D PRO...) you need wire HALL direct to USB +5V and Gnd cable and use additional components (resistor and trim pot) to fool USB circuit that he still handled 3,5v pots. Look here:
http://simhq.com/forum/ubbthreads.ph...ml#Post3161753
For joystick firmware the change from pots to HALL dont make difference - they continue receiving voltages changes. So no additional software or drives is need.
And finally: HALL is cheap.
(But some joystick makers prefer use 0,09U$ pots... Laudable exception is CH that use ~5,00U$ ones.)
Sokol1